LT8619/LT8619-5
1
Rev. B
For more information www.analog.com
TYPICAL APPLICATION
FEATURES DESCRIPTION
60V, 1.2A Synchronous Monolithic Buck
Regulator with 6µA Quiescent Current
The LT
®
8619 is a compact, high efficiency, high speed
synchronous monolithic step-down switching regulator
that consumes only 6μA of quiescent current. The LT8619
can deliver 1.2A of continuous current. Top and bottom
power switches are included with all necessary circuitry
to minimize the need for external components. Low ripple
Burst Mode
®
operation enables high efficiency down to
very low output currents while keeping the output ripple
to 10mVP-P. A SYNC pin allows forced continuous mode
operation synchronized to an external clock. Internal com
-
pensation with peak current mode topology allows the use
of small inductors and results in fast transient response
and good loop stability. The EN/UV pin has an accurate 1V
threshold and can be used to program VIN undervoltage
lockout or to shut down the LT8619, reducing the input
supply current to below 0.6μA. The PG flag signals when
VOUT is within ±7.5% of the programmed output voltage.
The LT8619 is available in a small 16-lead MSOP and
10-lead 3mm × 3mm DFN packages with exposed pad
for low thermal resistance.
APPLICATIONS
n Wide Input Voltage Range: 3V to 60V
n Fast Minimum Switch-On Time: 30ns
n Ultralow Quiescent Current Burst Mode Operation:
n 6μA IQ Regulating 12VIN to 3.3VOUT
n 10mVP-P Output Ripple at No Load
n Synchronizable/Programmable Fixed Frequency
Forced Continuous Mode Operation: 300kHz
to2.2MHz
n High Efficiency Synchronous Operation:
n 92% Efficiency at 0.5A, 5VOUT from 12VIN
n 90% Efficiency at 0.5A, 3.3VOUT from 12VIN
n Low Dropout: 360mV at 0.5A
n Low EMI
n Accurate 1V Enable Pin Threshold
n Internal Soft-Start and Compensation
n Power Good Flag
n Small Thermally Enhanced 16-Lead MSOP Package
and 10-Lead (3mm × 3mm) DFN Packages
n 12V Automotive Systems
n 12V and 24V Commercial Vehicles
n 48V Electric and Hybrid Vehicles
n Industrial Supplies
All registered trademarks and trademarks are the property of their respective owners.
Efficiency at VOUT = 5V5V, 1.2A Step-Down Converter
L = 10µH, IHLP-2020BZ-01
= 48V
= 24V
= 12V
OSC
= 700kHz
Burst Mode
OPERATION
EFFICIENCY
f
V
V
V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
0.0001
0.001
0.01
EFFICIENCY (%)
POWER LOSS (W)
8619 TA01b
0.1
1
10
Efficiency at V
OUT
= 5V
POWER LOSS
LT8619-5 10µH
66.5k
OFF ON
0.1µF
22µF
8619 TA01a
1µF
2.2µF
V
IN
6V TO 60V
V
OUT
5V
1.2A
BST
SW
BIAS
PG
OUT
INTVCC
VIN
GNDSYNC
fOSC = 700kHz
EN/UV
RT
PG
100k
L = VISHAY IHLP-2020BZ-01
COUT
= TDK C3225X7R1C226K250
Document Feedback
LT8619/LT8619-5
2
Rev. B
For more information www.analog.com
ABSOLUTE MAXIMUM RATINGS
VIN, EN/UV ................................................................60V
BIAS .......................................................................... 30V
BST Pin Above SW Pin................................................4V
PG, SYNC, OUT. ..........................................................6V
FB ...............................................................................2V
(Notes 1, 2)
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT8619EDD#PBF LT8619EDD#TRPBF LGNP 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT8619IDD#PBF LT8619IDD#TRPBF LGNP 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT8619EMSE#PBF LT8619EMSE#TRPBF 8619 16-Lead Plastic MSOP –40°C to 125°C
LT8619IMSE#PBF LT8619IMSE#TRPBF 8619 16-Lead Plastic MSOP –40°C to 125°C
LT8619EMSE-5#PBF LT8619EMSE-5#TRPBF 86195 16-Lead Plastic MSOP –40°C to 125°C
LT8619IMSE-5#PBF LT8619IMSE-5#TRPBF 86195 16-Lead Plastic MSOP –40°C to 125°C
Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
TOP VIEW
11
GND
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
θJA = 43°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
10
9
6
7
8
4
5
3
2
1SW
BST
INTVCC
BIAS
FB*
VIN
EN/UV
RT
PG
SYNC
1
2
3
4
5
6
7
8
NC
VIN
NC
EN/UV
RT
PG
SYNC
GND
16
15
14
13
12
11
10
9
SW
SW
BST
NC
INTVCC
BIAS
FB/OUT*
FB/OUT*
TOP VIEW
17
GND
MSE PACKAGE
16-LEAD PLASTIC MSOP
θJA = 40°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
*FB FOR LT8619, OUT FOR LT8619-5
PIN CONFIGURATION
Operating Junction Temperature (Note 3)
LT8619E, LT8619E-5 .......................... –40°C to 125°C
LT8619I, LT8619I-5 ............................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
LT8619/LT8619-5
3
Rev. B
For more information www.analog.com
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VEN/UV = 2V unless otherwise noted (Notes 2, 3)
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switching Loop
VIN Minimum Input Voltage 3.0 V
VIN Quiescent Current at No Load VIN = 12V, VEN/UV = 0V
l
0.6
0.6
1.0
3.0
µA
µA
VIN = 12V, VOUT = 3.3V, RT = 66.5k, BIAS = VOUT, VSYNC = 0V
l
6
6
10
18
µA
µA
VIN = 12V, VOUT = 3.3V, RT = 66.5k, BIAS = VOUT, Floats SYNC 10 µA
VIN = 12V, VOUT = 3.3V, RT = 66.5k, BIAS = VOUT, VSYNC = INTVCC 3 mA
VIN Current in Regulation VIN = 12V, VOUT = 3.3V, RT = 66.5k, BIAS = VOUT, VSYNC = 0V
ILOAD = 100µA
ILOAD = 1mA
l
l
38
320
65
400
µA
µA
BIAS Pin Current Consumption VIN = 12V, VBIAS = 3.3V, ILOAD = 0.5A, fOSC = 700kHz 2.2 mA
Regulated Output Voltage LT8619-5, VIN = 12V, VSYNC = INTVCC, No Load
l
4.975
4.925
5.0
5.0
5.025
5.075
V
Feedback Voltage LT8619, VIN = 12V, VSYNC = INTVCC, No Load
l
0.796
0.788
0.8
0.8
0.804
0.812
V
V
Feedback Voltage Line Regulation LT8619, VIN = 4V to 50V, VSYNC = INTVCC (Note 5)
LT8619-5, VIN = 6V to 50V, VSYNC = INTVCC (Note 5)
l
l
±0.004
±0.004
±0.03
±0.03
%/V
%/V
Feedback Pin Input Current LT8619, VFB = 0.8V ±20 nA
Minimum On-Time LT8619, ILOAD = 0.5A, VSYNC = INTVCC l30 60 ns
Minimum Off-Time 100 150 180 ns
Top Switch Peak Current Limit l1.5 1.75 2.0 A
Bottom Switch Current Limit 1.8 A
Bottom Switch Reverse Current Limit VSYNC = INTVCC 0.55 A
Soft-Start Duration VIN = 12V, VOUT = 3.3V, No Load, COUT = 22µF 0.2 ms
EN/UV to PG High Delay CINTVCC = 1µF, VOUT = 3.3V, No Load, COUT = 22µF 0.66 ms
EN/UV to PG Low Delay 10 µs
Oscillator and SYNC
Operating Frequency RT = 162k l260 300 340 kHz
RT = 66.5k l630 700 770 kHz
RT = 20k l1.9 2.0 2.1 MHz
Synchronization Frequency fSYNC ≥ fOSC l0.3 2.2 MHz
SYNC Threshold Frequency Synchronization
Burst Mode Operation
Floats SYNC Pin, Pulse-Skipping Mode
Forced Continuous Mode
0.35
1.6
1
0.6
1.2
2.0
0.95
2.4
V
V
V
V
SYNC Pin Current Built-In Sourcing Current, VSYNC = 0V
Built-In Sinking Current, VSYNC = 3.3V
–0.2
3.0
µA
µA
LT8619/LT8619-5
4
Rev. B
For more information www.analog.com
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VEN/UV = 2V unless otherwise noted (Notes 2, 3)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All Voltages are referenced to ground unless otherwise
specified.
Note 3: The LT8619 is tested under pulse load conditions such that
TJ≈ TA. The LT8619E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization, and correlation with statistical process controls. The
LT8619I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 4: This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime.
Note 5: Guaranteed by design, not subject to test.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switch, Logic and Power Good
Top Switch On-Resistance ILOAD = 0.1A 0.45 Ω
Bottom Switch On-Resistance ILOAD = 0.1A 0.22 Ω
EN/UV Power-On Threshold EN/UV Rising l0.94 1.0 1.1 V
EN/UV Power-On Hysteresis 40 mV
EN/UV Shutdown Threshold EN/UV Falling l0.34 0.56 0.92 V
EN/UV Pin Current VEN/UV = 2V –100 100 nA
Overvoltage Threshold VFB/VOUT Rising Wrt. Regulated VFB/VOUT 3.75 %
Positive Power Good Threshold VFB/VOUT Rising Wrt. Regulated VFB/VOUT l5 7.5 10 %
Negative Power Good Threshold VFB/VOUT Rising Wrt. Regulated VFB/VOUT l–5 –7.5 –10 %
Positive Power Good Delay LT8619, VFB = 0.8V ↑ 0.9V to PG Low
LT8619-5, VOUT = 5V ↑ 5.6V to PG Low
LT8619, VFB = 0.9V ↓ 0.8V to PG High
LT8619-5, VOUT = 5.6V ↓ 5V to PG High
60
60
35
35
µs
µs
µs
µs
Negative Power Good Delay LT8619, VFB = 0.8V ↓ 0.7V to PG Low
LT8619-5, VOUT = 5V ↓ 4.4V to PG Low
LT8619, VFB = 0.7V ↑ 0.8V to PG High
LT8619-5, VOUT = 4.4V ↑ 5V to PG High
60
60
35
35
µs
µs
µs
µs
PG Leakage VPG = 3.3V, Power Good ±100 nA
PG VOL IPG = 100µA l0.01 0.3 V
LT8619/LT8619-5
5
Rev. B
For more information www.analog.com
TYPICAL PERFORMANCE CHARACTERISTICS
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
2MHz Efficiency at V
OUT
= 3.3V
8619 G04
V
= 12V
f
OSC
= 2MHz
FORCED
CONTINUOUS
MODE
PULSE-
SKIPPING
MODE
Burst Mode
OPERATION
L = 3.3µH
IHLP-2020AB-01
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
70
75
80
85
90
95
100
EFFICIENCY (%)
Efficiency at V
OUT
= 5V
8619 G05
FORCED CONTINUOUS MODE
Burst Mode OPERATION
L = 10µH, IHLP-2020BZ-01
f
OSC
= 700kHz
12V
24V
48V
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
OUT
8619 G06
Burst Mode OPERATION
= 700kHz
OSC
f
V
= 48V
= 24V
V
= 12V
L = 10µH, IHLP-2020BZ-01
V
V
(V)
0
10
20
30
40
50
60
70
75
80
85
90
95
100
EFFICIENCY (%)
Efficiency vs V
IN
8619 G07
V
OUT
= 3.3V
f
SW
= 700kHz
FORCED CONTINUOUS MODE
L = 10µH IHLP-2020BZ-01
0.5A LOAD
1.2A LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0.5
1
10
20
I
VIN
(µA)
VIN
8619 G09
f
OSC
= 700kHz
Burst Mode OPERATION
SHUTDOWN
12V
12V
60V
60V
2MHz Efficiency at VOUT = 3.3V Efficiency at VOUT = 5V Efficiency at VOUT = 3.3V
Efficiency vs VIN No Load IVIN at 700kHz No Load IVIN vs Temperature
700kHz Efficiency at VOUT = 5V 2MHz Efficiency at VOUT = 5V700kHz Efficiency at VOUT = 3.3V
V
(V)
1
10
100
0.1
1
10
100
1k
10k
I
VIN
(µA)
No Load I
VIN
at 700kHz
8619 G08
FORCED CONTINUOUS MODE
Burst Mode OPERATION
3.3V
5V
3.3V
3.3V
VOUT:
PULSE-
SKIPPING
MODE
SHUTDOWN
f
OSC
= 700kHz
NO LOAD
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
700kHz Efficiency at V
OUT
= 5V
8619 G01
V
= 12V
f
OSC
= 700kHz
FORCED
CONTINUOUS
MODE
PULSE-
SKIPPING
MODE
Burst Mode
OPERATION
L = 10µH
IHLP-2020BZ-01
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
700kHz Efficiency at V
OUT
= 3.3V
8619 G02
V
= 12V
f
OSC
= 700kHz
FORCED
CONTINUOUS
MODE
PULSE-
SKIPPING
MODE
Burst Mode
OPERATION
L = 10µH
IHLP-2020BZ-01
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
10k
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
2MHz Efficiency at V
OUT
= 5V
8619 G03
V
= 12V
f
OSC
= 2MHz
FORCED
CONTINUOUS
MODE
PULSE-
SKIPPING
MODE
Burst Mode
OPERATION
L = 4.7µH
IHLP-2020AB-01
LT8619/LT8619-5
6
Rev. B
For more information www.analog.com
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
= 12V
f
OSC
= 700kHz
NO LOAD
FORCED CONTINUOUS MODE
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
–1.00
–0.75
–0.50
–0.25
0
0.25
0.50
0.75
1.00
∆V
OUT
(%)
OUT
8619 G10
V
= 12V
V
OUT
= 3.3V
f
SW
= 700kHz
FORCED CONTINUOUS MODE
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
–0.2
–0.1
0
0.1
0.2
∆V
OUT
(%)
Load Regulation
8619 G11
V
OUT
= 2.4V, NO LOAD
f
SW
= 400kHz
FORCED CONTINUOUS MODE
V
(V)
1
10
100
–0.10
–0.05
0
0.05
0.10
∆V
OUT
(%)
8619 G12
SHUTDOWN THRESHOLD
POWER–ON THRESHOLD
EN/UV RISING
EN/UV FALLING
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
0.2
0.4
0.6
0.8
1.0
1.2
V
EN/UV
(V)
EN/UV Threshold
8619 G13
f
SW
= 700kHz
L = 10µH
IHLP-2020BZ-01
DUTY CYCLE (%)
0
20
40
60
80
100
1.5
1.6
1.7
1.8
1.9
2.0
CURRENT LIMIT (A)
8619 G14
VOUT = 3.3V
LOAD CURRENT = 100mA
TOP SWITCH
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
100
200
300
400
500
600
700
800
900
1000
RDS(ON) (mΩ)
Switch Resistance
8619 G15
BOTTOM SWITCH
V
OUT
= 3.3V
∆V
OUT
= –1%
f
SW
= 2MHz
L = 3.3µH, IHLP-2020AB-01
FORCED CONTINUOUS MODE
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
0
0.2
0.4
0.6
0.8
1.0
DROPOUT VOLTAGE (V)
8619 G16
EN/UV Threshold
Top FET Current Limit vs
Duty Cycle Switch Resistance
Dropout
VOUT = 3.3V Load Regulation Line Regulation
V
= 12V
V
OUT
= 3.3V, NO LOAD
FORCED CONTINUOUS MODE
f
SW
= 700kHz
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
–5
–4
–3
–2
–1
0
1
2
3
4
5
∆f
SW
(%)
SW
8619 G18
f
SW
= 2MHz
Dropout vs Temperature fSW
1.2A LOAD
NO LOAD
1.0A LOAD
0.5A LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
DROPOUT VOLTAGE (V)
8619 G17
V
OUT
= 3.3V, ∆V
OUT
= –1%
f
OSC
= 700kHz
FORCED CONTINUOUS MODE
(CONTINUOUS OPERATION
ABOVE MAX JUNCTION
TEMPERATURE MAY
PERMANENTLY
DAMAGE THE
DEVICE)
L = 10µH, IHLP-2020BZ-01
LT8619/LT8619-5
7
Rev. B
For more information www.analog.com
TYPICAL PERFORMANCE CHARACTERISTICS
V
OUT
= 3.3V
f
SW
= 2MHz
FORCED CONTINUOUS MODE
0.2A LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
20
40
60
80
100
120
MINIMUM ON-TIME (ns)
Minimum On Time
8619 G19
0.5A LOAD
NO LOAD
NO LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
140
150
160
170
180
MINIMUM OFF TIME (ns)
8619 G20
0.5A LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
–10.0
–7.5
–5.0
–2.5
0
2.5
5.0
7.5
10.0
POWER GOOD, OVERVOLTAGE THRESHOLD (%)
Power Good, Overvoltage Threshold
8619 G21
OV
PPG V
FB
RISING
PPG V
FB
FALLING
NPG V
FB
RISING
NPG V
FB
FALLING
V
FB
– V
PGTH
(mV)
0
20
40
60
80
100
0
25
50
75
100
POWER GOOD DELAY (µs)
8619 G22
V
OUT
= 1.6V, NO LOAD
f
SW
= 700kHz
FORCED CONTINUOUS MODE
V
FALLING
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
2.5
2.6
2.7
2.8
2.9
3.0
V
IN
UVLO (V)
IN
8619 G23
V
RISING
V
= 12V
V
OUT
= 3.3V
FORCED CONTINUOUS MODE
f
SW
= 2MHz
f
SW
= 700kHz
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
0
2
4
6
8
10
12
I
BIAS
(mA)
BIAS
8619 G24
Minimum Off-Time
Power Good, Overvoltage
Threshold
Power Good Delay VIN UVLO IBIAS vs Load
Minimum On-Time
IBIAS vs fSW IBIAS at 700kHz vs Temperature IBIAS at 2MHz vs Temperature
1.2A LOAD
1A LOAD
NO LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
2
4
6
8
10
I
BIAS
(mA)
BIAS
8619 G26
V
= 12V
V
OUT
= 3.3V
FORCED CONTINUOUS MODE
(CONTINUOUS OPERATION
ABOVE MAX JUNCTION
TEMPERATURE MAY
PERMANENTLY
DAMAGE THE
DEVICE)
BIAS = V
OUT
0.5A LOAD
TEMPERATURE (°C)
–50
–25
0
25
50
75
100
125
150
0
4
8
12
16
20
24
IBIAS (mA)
1.2A LOAD
1A LOAD
0.5A LOAD
NO LOAD
I
BIAS
at 2MHz vs Temperature
8619 G27
V
= 12V
V
OUT
= 5V
FORCED CONTINUOUS MODE
(CONTINUOUS OPERATION
ABOVE MAX JUNCTION
TEMPERATURE MAY
PERMANENTLY
DAMAGE THE
DEVICE)
BIAS = V
OUT
0.2
0.6
1.0
1.4
1.8
2.2
0
2
4
6
8
10
V
IN
= 12V
V
OUT
= 3.3V
L = 10µH
FORCED CONTINUOUS MODE
1A LOAD
NO LOAD
f
SW
(MHz)
I
BIAS
(mA)
8619 G25
LT8619/LT8619-5
8
Rev. B
For more information www.analog.com
TYPICAL PERFORMANCE CHARACTERISTICS
Forced Continuous Mode No Load
Switching Waveform
Forced Continuous Mode Switching
Waveform at Minimum On-time
Forced Continuous Mode Transient
Load Step from 10mA to 1A
Pulse-Skipping Mode Transient
Load Step from 10mA to 1A
Bust Mode Transient Load Step
from 10mA to 1A
Forced Continuous Mode
Frequency Synchronization
200ns/DIV
VOUT (AC)
2mV/DIV
IL
200mA/DIV
SW
10V/DIV
8619 G28
VIN = 12V, VOUT = 3.3V
f
SW
= 2MHz, L = 3.3μH, C
OUT
= 22μF
TOP = 200ns/DIV, BOT = 5ns/DIV,
PERSISTENCE MODE
IL
200mA/DIV
SW
20V/DIV
SW
(ZOOM IN)
10V/DIV
8619 G29
VIN = 53.7V, VOUT = 3.3V, 0.5A LOAD
fSW = 2MHz, L = 3.3μH, COUT = 22μF
20μs/DIV
VOUT
200mV/DIV
ILOAD
1A/DIV
SW
10V/DIV
8619 G30
VIN = 12V, VOUT = 3.3V
f
OSC
= 2MHz, L = 3.3μH, C
OUT
= 22μF
20μs/DIV 8619 G31
VOUT
200mV/DIV
ILOAD
1A/DIV
SW
10V/DIV
VIN = 12V, VOUT = 3.3V
f
OSC
= 2MHz, L = 3.3μH, C
OUT
= 22μF
20μs/DIV 8619 G32
VOUT
200mV/DIV
ILOAD
1A/DIV
SW
10V/DIV
VIN = 12V, VOUT = 3.3V
f
OSC
= 2MHz, L = 3.3μH, C
OUT
= 22μF
VOUT (AC)
20mV/DIV
SYNC
2V/DIV
SW
10V/DIV
SW (ZOOM IN)
10V/DIV
SYNC (ZOOM IN)
2V/DIV
8619 G33
V
OUT (AC, ZOOM IN)
20mV/DIV
TOP = 10μs/DIV, BOT = 200ns/DIV
VIN = 12V, VOUT = 3.3V, NO LOAD
fOSC = 700kHz, L = 10μH, COUT = 22μF
fSW (FREE RUNNING) = 700kHZ, fSYNC
= 1.2MHz
LT8619/LT8619-5
9
Rev. B
For more information www.analog.com
TYPICAL PERFORMANCE CHARACTERISTICS
EN/UV Shut Down
VOUT = 2.4V Start-Up Dropout
Performance
VOUT = 5V Start-Up Dropout
Performance
EN/UV Start-Up
1s/DIV
VOUT
1V/DIV
VIN
1V/DIV
PG
2V/DIV
SW
5V/DIV
8619 G34
VIN
VOUT
VOUT = 2.4V, 10Ω LOAD
fSW = 400kHz, L = 15μH, COUT = 47μF
PG 100k PULL-UP BY INTVCC
FORCED CONTINUOUS MODE
8619 G35
1s/DIV
VOUT
1V/DIV
VIN
1V/DIV
PG
2V/DIV
SW
5V/DIV
VIN
VOUT
VOUT = 5V, 10Ω LOAD
fSW = 700kHz, L = 10μH, COUT = 22μF
PG 100k PULL-UP BY INTVCC
FORCED CONTINUOUS MODE
8619 G36
100μs/DIV
VOUT
1V/DIV
EN/UV
2V/DIV
PG
2V/DIV
SW
10V/DIV
VIN = 12V, VOUT = 3.3V, NO LOAD
fOSC = 2MHz, L = 3.3μH, COUT = 22μF
FORCED CONTINUOUS MODE
8619 G37
2μs/DIV
VOUT
1V/DIV
EN/UV
2V/DIV
PG
2V/DIV
SW
10V/DIV
VIN = 12V, VOUT = 3.3V, NO LOAD
fOSC = 2MHz, L = 3.3μH, COUT = 22μF
FORCED CONTINUOUS MODE
LT8619/LT8619-5
10
Rev. B
For more information www.analog.com
PIN FUNCTIONS
NC (Pin 1, 3, 13, MSOP Only): No Connect. These pins
are not connected to the internal circuitry.
VIN (Pin 1/Pin 2): The VIN pin supplies current to the
LT8619 internal circuitry and to the internal topside power
switch. Be sure to place the positive terminal of the input
bypass capacitor as close as possible to the VIN pin, and
the negative capacitor terminal as close as possible to
the GND pin.
EN/UV (Pin 2/Pin 4): The LT8619 is shut down when this
pin is low and active when this pin is high. The EN/UV pin
power-on threshold is 1V. When forced below 0.56V, the
IC is put into a low current shutdown mode. Tie to VIN if
shutdown feature is not used. An external resistor divider
from VIN can be used to program the VIN UVLO.
RT (Pin 3/Pin 5): A resistor is tied between RT and ground
to set the switching frequency. When synchronizing, the
RT resistor should be chosen to set the LT8619 switch-
ing frequency equal to or below the synchronization fre-
quency. Do not apply external voltage to this pin.
PG (Pin 4/Pin 6): Open-Drain Power Good Output. PG
remains low until the FB pin is within ±7.5% of the final
regulation voltage. The PG pull-up resistor can be con-
nected to the INTVCC, VOUT or an external supply voltage
that is lower than 6V.
SYNC (Pin 5/Pin 7): External Clock Synchronization Input.
Tie to a clock source for synchronization to an external
frequency. During clock synchronization, the controller
enters forced continuous mode. Ground the SYNC pin for
Burst Mode operation. Connect to INTVCC to enable forced
continuous mode operation. Floating this pin will enable
pulse-skipping mode operation. During start-up, the con-
troller is forced to run in pulse-skipping mode. When in
pulse-skipping or forced continuous mode operation, the
I
Q
will be much higher compared to Burst Mode operation.
FB (Pin 6/Pin 9, 10, LT8619 Only): The LT8619 regulates
the FB pin to 0.8V. Connect the feedback resistor divider
tap to this pin. Also, connect a phase lead capacitor
between FB and VOUT. Typically, this capacitor is between
4.7pF to 10pF. Do not apply an external voltage to this pin.
OUT (Pin 9, 10, LT8619-5 MSOP Only): Connect to the
regulator output VOUT. The LT8619-5 regulates the OUT
pin to 5V. This pin connects to the internal 10MΩ feed-
back divider that programs the fixed output voltage.
BIAS (Pin 7/Pin 11): The internal regulator will draw cur-
rent from BIAS instead of VIN when the BIAS pin is tied
to a voltage higher than 3.1V. For switching regulator
output voltages of 3.3V and above, this pin should be tied
to VOUT. If this pin is tied to a supply other than VOUT, use
a 1μF local bypass capacitor on this pin.
INTVCC (Pin 8/Pin 12): Internal 3.3V Regulator Output.
The internal power drivers and control circuits are pow-
ered from this voltage. INTVCC maximum output current
is 20mA. INTVCC current will be supplied from BIAS if
VBIAS > 3.1V, otherwise current will be drawn from VIN.
Voltage on INTVCC will vary between 2.8V and 3.3V when
V
BIAS
is between 3.0V and 3.5V. Decouple this pin to GND
with at least a 1μF low ESR ceramic capacitor. Do not load
the INTVCC pin with external circuitry.
BST (Pin 9/Pin 14): This pin is used to provide a drive
voltage, higher than the input voltage, to the topside
power switch. Place a 0.1μF boost capacitor as close as
possible to theIC.
SW (Pin 10/Pin 15, 16): The SW pin is the output of the
internal power switches. Connect this pin to the inductor
and boost capacitor. This node should be kept small on
the PCB for good performance.
GND (Exposed Pad Pin 11/Pin 8, Exposed Pad Pin 17):
Ground. The exposed pad must be connected to the nega-
tive terminal of the input capacitor and soldered to the
PCB in order to lower the thermal resistance.
(DFN/MSOP)
LT8619/LT8619-5
11
Rev. B
For more information www.analog.com
BLOCK DIAGRAM
–
+
LOGIC
RC
VC
ISS
SW
GND
FB/OUT
0.74V
NPG
–
+
OV
OV
OV
0.86V
8619 BD
0.83V
PG
SYNC
RT
EN/UV
R3
OPT
1V ENABLE
VOUT = 5V
CB
CINTVCC
CIN
COUT
CSS
CC
C1
VOUT
R1
R4
OPT
RT
R2
L
BST
BIAS
INTVCC
INTVCC
3.3V
LDO
VIN
0.8V VREF
+ – +
EA
SLOPE
COMP
BURST
DETECT
OSC
0.3MHz–2.2MHz
GLITCH
FILTER
–+
SR
ICMP
VIN
VIN
Q
CLK
–
+
PPG
–
+
UVLO
PG
LT8619/LT8619-5
12
Rev. B
For more information www.analog.com
OPERATION
The LT8619 is a monolithic, constant frequency current
mode step-down DC/DC converter. An oscillator, with fre-
quency set using a resistor on the RT pin, turns on the
internal top power switch at the beginning of each clock
cycle. Current in the inductor then increases until the cur-
rent comparator trips and turns off the top power switch.
The peak inductor current at which the top switch turns off
is controlled by the voltage on the internal VC node. The
error amplifier servos the VC node by comparing the volt-
age on the FB pin with an internal 0.8V reference. When
the load current increases, it causes a reduction in the
feedback voltage relative to the reference leading the error
amplifier to raise the VC voltage until the average induc-
tor current matches the new load current. When the top
power switch turns off, the bottom power switch turns on
until the next clock cycle begins or inductor current falls
to zero (Burst Mode operation or pulse-skipping mode).
If overload conditions result in more than 1.8A flowing
through the bottom switch, the next clock cycle will be
delayed until the switch current returns to a safe level.
If the EN/UV pin is low, the LT8619 is shut down and
draws less than 0.6µA from the input. When the EN/UV
pin is above 1V, the switching regulator starts operation.
First, the internal LDO powers up, followed by the switch-
ing regulator 200μs soft-start ramp. During the soft-start
phase, the switcher operates in pulse-skipping mode and
gradually switches to forced continuous mode when VOUT
approaches the set point (if SYNC pin is forced high or
connected to an external clock). Typically, upon EN/UV
rising edge, it takes about 660μs for the switcher output
voltage to reach regulation and PG to be asserted.
To optimize efficiency at light loads, configure the LT8619
to operate in Burst Mode by grounding the SYNC pin.
At light load, in between bursts, all circuitry associated
with controlling the output switch is shut down, reducing
the input supply current. In a typical application, 6μA will
be consumed from the supply when regulating with no
load. Float the SYNC pin to enable pulse-skipping mode
operation. While in pulse-skipping mode, the oscillator
operates continuously and the bottom power switch turns
off when the inductor current falls to zero. During light
loads, switch pulses are skipped to regulate the output
and the quiescent current will be higher than Burst Mode
operation. Connecting the SYNC pin to INTV
CC
enables
forced continuous mode operation. In forced continuous
mode, the inductor current is allowed to reverse and the
switcher operates at a fixed frequency. If a clock is applied
to the SYNC pin, the part operates in forced continuous
mode and synchronizes to the external clock frequency;
with the rising SW signal synchronized to the external
clock positive edge.
To improve efficiency across all loads, supply current
to internal circuitry can be sourced from the BIAS pin
when biased above 3.1V. Else, the internal circuitry will
draw current from V
IN
. The BIAS pin should be connected
to VOUT if the LT8619 output is programmed to 3.3V or
above.
An overvoltage comparator, OV, guards against transient
overshoots. If VFB is higher than 0.83V, the OV compara-
tor trips, disables the top MOSFET and turns on the bot-
tom power switch until the next clock cycle begins or the
inductor reverse current reaches 0.55A. With high reverse
current, both top and bottom MOSFETs shut off till the
next cycle. Positive and negative power good compara-
tors pull the PG pin low if the FB voltage varies more than
±7.5% (typical) from the set point.
The oscillator reduces the LT8619’s operating frequency
when the voltage at the FB pin is low. This frequency
foldback helps to control the inductor current when the
output voltage is lower than the programmed value which
occurs during overcurrent conditions.
LT8619/LT8619-5
13
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
Achieving Ultralow Quiescent Current
To enhance efficiency at light loads, the LT8619 enters into
Burst Mode operation, which keeps the output capacitor
charged to the desired output voltage while minimizing the
input quiescent current and output ripple voltage. In Burst
Mode operation the LT8619 delivers single small pulses of
current to the output capacitor followed by sleep periods
where the output power is supplied by the output capacitor.
While in sleep mode the LT8619 consumes less than 6μA.
As the output load decreases, the frequency of single cur-
rent pulses decreases (see Figure1) and the percentage
of time the LT8619 is in sleep mode increases, result-
ing in much higher light load efficiency than for typical
converters. For a typical application, when the output is
not loaded, by maximizing the time between pulses, the
regulator quiescent approaches 6µA. Therefore, to opti-
mize the quiescent current performance at light loads,
the current in the feedback resistor divider must be mini-
mized as it appears to the output as load current (See FB
Resistor Network section).
While in Burst Mode operation, the current limit of the
top switch is approximately 380mA resulting in output
voltage ripple shown in Figure2. Increasing the output
capacitance will decrease the output ripple proportionally.
As load ramps upward from zero, the switching frequency
will increase but only up to the switching frequency
programmed by the resistor at the RT pin as shown in
Figure1. The output load at which the LT8619 reaches
the programmed frequency varies based on input voltage,
output voltage, and inductor choice.
For some applications it is desirable for the LT8619 to
operate in pulse-skipping mode, offering two major dif-
ferences from Burst Mode operation. First, the minimum
inductor current clamp present in Burst Mode operation
is removed, providing a smaller packet of charge to the
output capacitor and reduce the output ripple voltage.
For a given load, the chip awake more often, resulting in
higher supply current compared to Burst Mode opera-
tion. Second is that full switching frequency is reached
at lower output load than in Burst Mode operation (see
Figure3). To enable pulse-skipping mode, leave the SYNC
pin floating. Tying the SYNC pin to INTVCC node enables
the programmed switching frequency at no load.
Figure1. Burst Frequency vs Load Current
8619 F02
V
OUT
(AC)
10mV/DIV
IL
200mA/DIV
SW
10V/DIV
SW (ZOOM IN)
10V/DIV
IL (ZOOM IN)
200mA/DIV
V
OUT (AC, ZOOM IN)
10mV/DIV
TOP = 20ms/DIV, BOT = 1μs/DIV
Figure2. Burst Mode Operation Waveform with
VIN = 12V, VOUT = 3.3V at No Load, RT = 66.5k,
L = 10μH, COUT = 22μF
V
OUT
= 3.3V
f
OSC
= 700kHz
L = 10µH
V
IN
(V)
0
10
20
30
40
50
60
0
50
100
150
200
250
300
350
400
LOAD CURRENT (mA)
8619 F03
PULSE-SKIPPING MODE
Burst Mode OPERATION
V
= 12V
V
OUT
= 3.3V
f
OSC
= 700kHz
L = 10µH
Burst Mode OPERATION
LOAD CURRENT (mA)
0.001
0.01
0.1
1
10
100
1k
0.01
0.1
1
10
100
1k
f
SW
(kHz)
8619 F01
Figure3. Minimum Load for Full Frequency Operation
vs VIN in Burst Mode Operation and Pulse-Skipping
Mode Setting
LT8619/LT8619-5
14
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
FB Resistor Network
The output voltage is programmed with a resistor divider
between VOUT and the FB pin. Choose the resistor values
according to:
R1=R2 VOUT
0.8V – 1
⎛
⎝
⎜⎞
⎠
⎟
Reference designators refer to the Block Diagram. 1%
resistors are recommended to maintain output voltage
accuracy.
If low input quiescent current and good light-load effi-
ciency are desired, use a large resistor value for the FB
resistor divider. The current flowing in the divider acts as
a load current, and will increase the no-load input current
to the converter, which is approximately:
IQ=5.2µA +VOUT
R1+R2
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
VOUT
VIN
⎛
⎝
⎜
⎜
⎜
⎞
⎠
⎟
⎟
⎟
1
η
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
where 5.2μA is the quiescent current of the LT8619 and
the second term is the current in the feedback divider
reflected to the input of the buck operating at its light load
efficiency, η. For a 3.3V application with R1 = 1M and
R2 = 316k, the feedback divider draws 2.5μA from VOUT.
With V
IN
= 12V and η = 85%, this adds 0.8μA to the 5.2μA
quiescent current resulting in 6μA quiescent current from
the 12V supply. Note that this equation implies that the
no-load current is a function of VIN; this is plotted in the
Typical Performance Characteristics section.
When using large FB resistors, a 4.7pF to 10pF phase
lead capacitor, C1, should be connected from VOUT to FB.
Setting the Switching Frequency
The LT8619 uses a constant frequency PWM architec-
ture that can be programmed to switch from 300kHz to
2.2MHz by using a resistor tied from the RT pin to ground.
The R
T
resistor required for a desired oscillator frequency
can be roughly obtain using:
RT=
50.07
fOSC
– 5
where RT is in kΩ and fOSC is the desired switching fre-
quency in MHz.
Table 1 and Figure4 show the typical RT value for a
desired oscillator frequency.
Table1. Oscillator Frequency vs RT Value (1% Standard Value)
fOSC (MHz) RT (kΩ) fOSC (MHz) RT (kΩ)
0.3 162 1.4 30.9
0.4 121 1.6 26.1
0.5 95.3 1.8 22.6
0.6 78.7 2.0 20.0
0.7 66.5 2.2 17.8
0.8 57.6
0.9 51.1
1.0 45.3
1.2 36.5
Figure4. Oscillator Frequency vs RT Value
Operating Frequency Selection and Trade-Offs
Selection of the operating frequency is a trade-off between
efficiency, component size, and input voltage range. The
advantage of high frequency operation is that smaller
inductor and capacitor values may be used. The disadvan-
tages are lower efficiency and a smaller input voltage range.
For force continuous mode operation, the highest oscil-
lator frequency (fOSC(MAX)) for a given application can be
approximately given by the 1st order equation:
fOSC(MAX) =ILOADRSW(BOT) +VOUT
tON(MIN) VIN – ILOADRSW(TOP) +ILOADRSW(BOT)
( )
Where VIN is the input voltage, VOUT is the output volt-
age, RSW(TOP) and RSW(BOT) are the internal switch on
resistance (~0.45Ω, ~0.22Ω, respectively) and tON(MIN)
R
T
(kΩ)
0
20
40
60
80
100
120
140
160
0.2
0.6
1.0
1.4
1.8
2.2
f
OSC
(MHz)
8619 F04
LT8619/LT8619-5
15
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
is the minimum top switch on-time at the loading condi-
tion as shown in Figure5. Figure6 shows the relation-
ship between the maximum input voltage vs the switching
frequency. If a smaller RT is selected, to ensure that the
regulator is switching at the higher frequency as illus-
trated in Figure4, the maximum input supply voltage has
to be lowered; and it needs to be further reduced if the
load is decreased or removed.
For forced continuous mode, if there is a momentarily V
IN
voltage surge higher than the voltage shown in Figure6,
resulting in minimum on-time operation, an overvoltage
comparator guards against transient overshoots as well
as other more serious conditions that may overvoltage the
output. When the VFB voltage rises by more than 3.75%
above its nominal value, the top MOSFET is turned off
and the bottom MOSFET is turned on. At this moment,
the output voltage continues to increase until the inductor
current reverses. The actual peak output voltage will be
higher than 3.75%, depending on external components
value, loading condition and output voltage setting. The
bottom MOSFET remains on continuously until the induc-
tor current exceeds the bottom MOSFET reverse current
or overvoltage condition is cleared. With high reverse cur-
rent, both top and bottom MOSFETs shut off till the next
clock cycle.
Low Supply Operation
The LT8619 is designed to remain operational during
short line transients when the input voltage may briefly
dip below 3.0V. Below this voltage, the INTV
CC
voltage
might drop to a point that is not able to provide adequate
gate drive voltage to turn on the MOSFET. The LT8619 has
two circuits to detect this undervoltage condition. A UVLO
comparator monitors the INTVCC voltage to ensure that it
is above 2.8V during startup; once in regulation, the chip
continues to operate as long as INTV
CC
stays above 2.65V.
If this UVLO comparator trips, the chip is shut down until
INTVCC recovers. Another comparator monitors the VIN
supply voltage, add a resistor divider from VIN to EN/UV
to turn off the regulator if VIN dips below the undesirable
voltage.
The LT8619 is capable of a maximum duty cycle of greater
than 99%, and the VIN-to-VOUT dropout is limited by the
RDS(ON) of the top switch. In deep dropout, the loop
attempt to turn on the top switch continuously. However,
the top switch gate drive is biased from the floating boot-
strap capacitor CB, which normally recharges during each
off cycle; in dropout, this capacitor loses its refresh cycle
and charge depleted. A comparator detects the drop in
boot-strap capacitor voltage, forces the top switch off and
recharges the capacitor.
Figure5. Minimum On-Time vs Load Current
Figure6. Forced Continuous Mode Maximum Input
Voltage vs Switching Frequency
V
OUT
= 3.3V
f
SW
= 2MHz
L = 3.3µH
FORCED CONTINUOUS MODE
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
0
10
20
30
40
50
60
70
80
MINIMUM ON-TIME (ns)
8619 F05
V
OUT
= 3.3V
L = 10µH
FORCED CONTINUOUS MODE
0.2A LOAD
f
SW
(MHz)
0.2
0.6
1.0
1.4
1.8
2.2
0
10
20
30
40
50
60
MAXIMUM V
IN
(V)
8619 F06
0.5A
LOAD
NO LOAD
High Supply Operation
For Burst Mode operation or pulse-skipping mode, V
IN
voltage may go as high as the absolute maximum rating
of 60V regardless of the frequency setting; however, the
LT8619 will reduce the switching frequency as necessary
to regulate the output voltage.
LT8619/LT8619-5
16
Rev. B
For more information www.analog.com
For low VIN applications that cannot allow deviation from
the programmed oscillator frequency, use the following
formula to set the switching frequency:
VIN(MIN) =
V
SW(BOT) +
V
OUT
1– tOFF(MIN) • fOSC
+VSW(TOP) – VSW(BOT)
where VIN(MIN) is the minimum input voltage without
skipped cycles, VOUT is the output voltage, VSW(TOP) and
VSW(BOT) are the internal switch drops (~0.54V, ~0.264V,
respectively at maximum load), fOSC is the oscillating fre-
quency (set by RT), and tOFF(MIN) is the minimum switch-
ing off-time. Note that higher switching frequency will
increase the minimum input voltage below which cycles
will be dropped to achieve higher duty cycle.
Inductor Selection and Maximum Output Current
The LT8619 is designed to minimize solution size by
allowing the inductor to be chosen based on the output
load requirements of the application. During overload or
short-circuit conditions the LT8619 safely tolerates opera-
tion with a saturated inductor through the use of a high
speed peak-current mode architecture.
A good first choice for the inductor value is:
L=2
V
OUT +
V
SW(BOT)
fOSC
where fOSC is the switching frequency in MHz, VOUT is
the output voltage, VSW(BOT) is the bottom switch drop
(~0.264V) and L is the inductor value in μH.
To avoid overheating and poor efficiency, an inductor
must be chosen with an RMS current rating that is greater
than the maximum expected output load of the applica-
tion. In addition, the saturation current (typically labeled
ISAT) rating of the inductor must be higher than the load
current plus one-half of inductor ripple current:
ISAT >ILOAD(MAX) +ΔIL(MAX)
2
APPLICATIONS INFORMATION
where ILOAD(MAX) is the maximum output load for a given
application and ∆IL(MAX) is the inductor ripple current as
calculated in the following equation:
ΔIL(MAX) =1
fOSC •L VOUT 1– VOUT
VIN(MAX)
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
As a quick example, an application requiring 1A output
current should use an inductor with an RMS rating of
greater than 1A and an ISAT of greater than 1.5A. During
long duration overload or short-circuit conditions, the
inductor RMS rating requirement is greater to avoid over-
heating of the inductor. To push for high efficiency, select
an inductor with low series resistance (DCR), preferably
below 0.04Ω, and the core material should be intended
for high frequency application. However, achieving this
requires a large size inductor. An inductor with DCR
around 0.1Ω is generally a good compromise for both
efficiency and board area, at the expense of trimming 1%
to 2% from the efficiency number.
The LT8619 limits the peak switch current in order to pro-
tect the switches and the system from overload faults. The
top switch current limit (ILIM) is at least 1.5A. The induc-
tor value must then be sufficient to supply the desired
maximum output current (ILOAD(MAX)), which is a function
of the switch current limit (ILIM) and the ripple current:
ILOAD(MAX) =ILIM –Δ
I
L
2
Therefore, the maximum output current that the LT8619
will deliver depends on the switch current limit, the induc-
tor value, and the input and output voltages. The inductor
value may have to be increased if the inductor ripple cur-
rent does not allow sufficient maximum output current
(I
LOAD(MAX)
) given the switching frequency, and maximum
input voltage used in the desired application.
In order to achieve higher light load efficiency, more
energy must be delivered to the output during single small
pulses in Burst Mode operation such that the LT8619 can
LT8619/LT8619-5
17
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
stay in sleep mode longer between each pulse. This can
be achieved by using a larger value inductor, and should
be considered independent of switching frequency when
choosing an inductor. For example, while a lower inductor
value would typically be used for a high switching fre-
quency application, if high light load efficiency is desired,
a higher inductor value should be chosen.
The optimum inductor for a given application may differ
from the one indicated by this design guide. A larger value
inductor provides a higher maximum load current and
reduces the output voltage ripple. For applications requir-
ing smaller load currents, the value of the inductor may
be lower and the LT8619 may operate with higher ripple
current. This allows you to use a physically smaller induc-
tor, or one with a lower DCR resulting in higher efficiency.
Be aware that low inductance may result in discontinuous
mode operation, which further reduces maximum load
current.
For details of maximum output current and discontinuous
operation, see Analog Devices’s Application Note 44.
Input Capacitor
Step-down regulators draw current from the input sup-
ply in pulses with very fast rise and fall times. The input
capacitor is required to reduce the resulting voltage rip-
ple at the LT8619 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
In continuous mode, the input capacitor RMS current is
given by:
IRMS(MAX) ≈ILOAD(MAX)
VOUT VIN – VOUT
( )
V
IN
This equation has a maximum RMS current at VIN =
2VOUT, where IRMS(MAX) = ILOAD(MAX)/2.
Bypass the input of the LT8619 circuit with a 2.2μF to
10μF ceramic capacitor of X7R or X5R type placed as
close as possible to the VIN and GND pin. Y5V types have
poor performance over temperature and applied voltage,
and should not be used. Note that larger input capacitance
is required when a lower switching frequency is used.
If the input power source has high impedance, or there
is significant inductance due to long wires or cables, a
ceramic input capacitor combined with the trace or cable
inductance forms a high quality (underdamped) tank cir-
cuit. If the LT8619 circuit is plugged into a live supply, the
input voltage can ring to twice its nominal value, possibly
exceeding the LT8619’s voltage rating. This situation is
easily avoided (see Analog Devices Application Note88),
by adding a lossy electrolytic capacitor in parallel with the
ceramic capacitor.
Output Capacitor and Output Ripple
The output capacitor has two essential functions. Along
with the inductor, it filters the square wave generated
by the LT8619 to produce the DC output. In this role it
determines the output ripple, thus low impedance at the
switching frequency is important. The second function
is to store energy in order to satisfy transient loads and
stabilize the LT8619’s control loop. The current slew rate
of a regulator is limited by the inductor and feedback loop.
When the amount of current required by the load changes,
the initial current deficit must be supplied by the output
capacitor until the feedback loop reacts and compensates
for the load changes. Ceramic capacitors have very low
equivalent series resistance (ESR) and provide the best
ripple performance. For good starting values, see the
Typical Application section.
Transient performance can be improved with a higher
value capacitor and the addition of a feedforward capaci-
tor placed between VOUT and FB. Increasing the output
capacitance will also decrease the output voltage ripple. A
lower value of output capacitor can be used to save space
and cost but transient performance will suffer and may
cause loop instability. See the Typical Application in this
data sheet for suggested capacitor values.
Ceramic Capacitors
When choosing a capacitor, special attention should be
given to the manufacturer’s data sheet in order to accu-
rately calculate the effective capacitance under the rel-
evant bias voltage and operating temperature conditions.
Ceramic dielectrics can offer near ideal performance as
LT8619/LT8619-5
18
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
an output capacitor, i.e. high volumetric efficiency with
extremely low equivalent resistance. There is a downside
however; the high K dielectric material exhibits a substan-
tial temperature and voltage coefficient, meaning that its
capacitance varies depending on the operating tempera-
ture and applied voltage. X7R capacitors provide a range
intermediate capacitance values which varies only ±15%
over the temperature range of –55°C to 125°C. The Y5V
capacitance can vary from 22% to –82% over the –30°C
to 85°C temperature range and should not be used for the
LT8619 application.
Figure7 shows the voltage coefficient of four different
ceramic 22μF capacitors, all of which are rated for 16V
operation. Note that with the exception of the X7R in the
1210 and 1812 package, the capacitors lose more than
30% of their capacitance when biased at more than half of
the rated voltage. Typically, as the package size increases,
the bias voltage coefficient decreases. If the voltage coef-
ficient of a big ceramic capacitor in a particular pack-
age size is not acceptable; multiple smaller capacitors
with less voltage coefficient can be placed in parallel as
an effective means of meeting the capacitance require-
ment. Not All Capacitors are Interchangeable. A wrong
capacitor selection can degrade the circuit performance
considerably.
Ceramic capacitors can also cause problems due to their
piezoelectric nature. During Burst Mode operation, the
switching frequency depends on the load current, and at
very light loads the LT8619 can excite the ceramic capaci-
tor at frequencies that may generate audible noise. Since
the LT8619 operates at a lower inductor current during
Burst Mode operation, the noise is typically very quiet
to a casual ear. If this is unacceptable, consider using
a high performance tantalum or electrolytic capacitor at
the output instead. Low noise ceramic capacitors are also
available.
Ceramic capacitors are also susceptible to mechanical
stress which can result in significant loss of capacitance.
The most common sources of mechanical stress includes
bending or flexure of the PCB, contact pressure during in
circuit parameter testing, and direct contact by a solder-
ing iron tip. Consult the manufacturer’s application notes
for additional information regarding ceramic capacitor
handling.
Enable Pin
The LT8619 is in shutdown when the EN/UV pin is low
and active when the pin is high. The power-on threshold
of theEN comparator is 1.0V, with 40mV of hysteresis,
once EN/UV drops below this power-on threshold, the
MOSFETs are disabled, but the internal biasing circuit
stays alive. When forced below 0.56V, all the internal
blocks are disabled and the IC is put into a low current
shutdown mode. The EN/UV pin can be tied to VIN if the
shutdown feature is not used.
Adding a resistor divider from V
IN
to EN/UV programs the
LT8619 to regulate the output only when VIN is above a
desired voltage (see the Block Diagram). Typically, this
threshold, V
IN(EN/UV)
, is used in situations where the input
supply is current limited, or has a relatively high source
resistance. A switching regulator draws constant power
from the source, so source current increases as source
voltage drops. This looks like a negative resistance load
to the source and can cause the source to current limit
or latch low under low source voltage conditions. The
VIN(EN/UV) threshold prevents the regulator from operating
at source voltages where the problems might occur. This
Figure7. Ceramic Capacitor Voltage Coefficient
X7R, 1210
X7R, 1812
X5R, 1206
X5R, 0805
C3225X7R1C226K250
C4532X7R1C226M200
C3216X5R1C226M160
C2012X5R1C226K125
DC BIAS VOLTAGE (V)
0
2
4
6
8
10
12
14
16
–100
–80
–60
–40
–20
0
20
CAPACITANCE CHANGE (%)
8619 F09
LT8619/LT8619-5
19
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
threshold can be adjusted by setting the values R3 and
R4 such that they satisfy the following equation:
VIN(EN/UV) =1+R3
R4
⎛
⎝
⎜⎞
⎠
⎟• 1V
where the LT8619 will remain off until VIN is above
VIN(EN/UV). Due to the comparator’s hysteresis, switching
will not stop until the input falls slightly below VIN(EN/UV).
When in Burst Mode operation for light load currents,
the current through the VIN(EN/UV) resistor network can
easily be greater than the supply current consumed by
the LT8619. Therefore, the V
IN(EN/UV)
resistors should
be large enough to minimize their impact on efficiency
at low loads.
INTVCC Regulator
An internal low dropout (LDO) regulator produces the 3.3V
supply from VIN that powers the drivers and the internal
bias circuitry. The INTVCC can supply enough current for
the LT8619’s circuitry and must be bypassed to ground
with at least a 1μF ceramic capacitor. Good bypassing is
necessary to supply the high transient currents required
by the power MOSFET gate drivers. To improve efficiency
the internal LDO can draw current from the BIAS pin when
the BIAS pin is at 3.1V or higher. Typically the BIAS pin can
be tied to the output of the switching regulator, or can be
tied to an external supply which must also be at 3.3V or
above. If BIAS is connected to a supply other than VOUT,
be sure to bypass with a local ceramic capacitor. If the
BIAS pin is below 3.0V, the internal LDO will consume
current from V
IN
. Applications with high input voltage and
high switching frequency where the internal LDO pulls
current from V
IN
will increase die temperature because
of the higher power dissipation across the LDO. Do not
connect an external load to the INTVCC pin.
Output Power Good
When the LT8619’s output voltage is within the ±7.5%
window of the regulation point, the open-drain PG pin
goes high impedance and is typically pulled high with an
external resistor. Otherwise, the internal open-drain tran-
sistor will pull the PG pin low. The PG pin is also actively
pulled low during several fault conditions: EN/UV pin is
below 1V, INTVCC drops below its UVLO threshold, VIN is
too low, or thermal shutdown.
Synchronization
Synchronizing the LT8619 oscillator to an external fre-
quency can be done by connecting a square wave (with
20% to 80% duty cycle) to the SYNC pin. The square wave
amplitude should have valleys that are below 0.4V and
peaks above 2V (up to 6V). During frequency synchroni-
zation, the part operates in forced continuous mode with
the SW rising edge synchronized to the SYNC positive
edge. The LT8619 may be synchronized over a 300kHz
to 2.2MHz range. The RT resistor must be chosen to set
the LT8619 switching frequency equal or below the lowest
synchronization input. For example, if the synchroniza-
tion signal will be 500kHz and higher, the RT should be
selected for 500kHz.
Start-Up Inrush Current, Short-Circuit Protection
Upon start-up, the internal soft-start action regulates
the VOUT slew rate; the LT8619 provides the maximum
rated output current to charge up the output capacitor
as quickly as possible. During start-up, if the output is
overloaded, the regulator continues to provide the maxi-
mum sourcing current to overcome the output load, but
at the same time, the bottom switch current is monitored
such that if the inductor current is beyond the safe levels,
switching of the top switch will be delay until such time
as the inductor current falls to safe levels.
Once the soft-start period has expired and the FB voltage
is higher than 0.74V, the LT8619 switching frequency will
be folded back if the external load pulls down the output.
At the same time, the bottom switch current will continue
to be monitored to limit the short-circuit current. Figure 8
shows the frequency foldback transfer curve and Figure 9
shows the short circuit waveform. During this overcurrent
condition, if the SYNC pin is connected to a clock source,
the LT8619 will get out from the synchronization mode.
LT8619/LT8619-5
20
Rev. B
For more information www.analog.com
R
T
= 20kΩ
V
FB
(V)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0
0.5
1.0
1.5
2.0
2.5
f
SW
(MHz)
8619 F08
Figure8. Frequency Foldback Transfer Function
Figure9. Short-Circuit Waveform with VIN = 12V,
VOUT = 3.3V, fOSC = 2MHz, L = 4.7μH, COUT = 22μF
VIN
V
IN
LT8619
EN/UV
GND
8619 F10
PCB Layout
For proper operation and minimum EMI, care must be
taken during printed circuit board (PCB) layout. Figure11
and Figure12 show the recommended component place-
ment with trace, ground plane and via locations. Note that
large, switched currents flow in the LT8619’s VIN, SW,
GND pins, and the input capacitor. The loop formed by
these components should be as small as possible by plac
-
ing the capacitor adjacent to the VIN and GND pins. When
using a physically large input capacitor, the resulting loop
may become too large in which case using a small case/
value capacitor placed close to the VIN and GND pins plus
a larger capacitor further away is preferred. These com-
ponents, along with the inductor and output capacitor,
should be placed on the same side of the circuit board,
and their connections should be made on that layer. Place
a local, unbroken ground plane under the application cir-
cuit on the layer closest to the surface layer. The SW and
BST nodes should be as small as possible. Finally, keep
the FB and RT nodes small so that the ground traces will
shield them from the SW and BST nodes. The exposed
pad on the bottom of the package must be soldered to
ground so that the pad is connected to ground electrically
and also acts as a heat sink thermally. To keep thermal
resistance low, extend the ground plane as much as pos-
sible, and add thermal vias under and near the LT8619 to
additional ground planes within the circuit board and on
the bottom side.
High Temperature Output Current Considerations
The maximum practical continuous load that the LT8619
can drive, while rated at 1.2A, actually depends upon both
the internal current limit (refer to the Typical Performance
Characteristics section) and the internal temperature
which depends on operating conditions, PCB layout and
airflow.
APPLICATIONS INFORMATION
5μs/DIV
VOUT
1V/DIV
ISHORT
10A/DIV
IL
0.5A/DIV
SW
10V/DIV
8619 F09
Reversed Input Protection
Load protection may be necessary in systems where the
output will be held high when the input to the LT8619 is
absent. This may occur in battery charging applications or
in battery backup systems where a battery or some other
supply is diode ORed with the LT8619’s output. If the VIN
pin is allowed to float and the EN/UV pin is held high (either
by a logic signal or because it is tied to VIN), then the
LT8619’s internal circuitry will pull its quiescent current
through its SW pin. This is acceptable if the system can tol-
erate several μA in this state. If the EN/UV pin is grounded
the SW pin current will drop to near 1µA. However, if the
VIN pin is grounded while the output is held high, regard-
less of EN/UV, parasitic body diodes inside the LT8619
can pull current from the output through the SW pin and
the VIN pin. Figure10 shows a connection of the VIN and
EN/UV pins that will allow the LT8619 to run only when
the input voltage is present and that protects against a
shorted or reversed input.
Figure10. Reverse VIN Protection
LT8619/LT8619-5
21
Rev. B
For more information www.analog.com
APPLICATIONS INFORMATION
EN/UV
PG
SYNC
RT
GND
SW
VOUT
VIN INTVCC
BST
BIAS VOUT
FB/OUT
+
8619 F12
EN/UV
PG
RT
SYNC RT
GND
SW
VOUT
VIN
BST
INTVCC
BIAS
VOUT
FB/OUT
+
8619 F11
Figure11. Recommended PCB Layout for LT8619 10-Pin DFN
Figure12. Recommended PCB Layout for LT8619 16-Pin MSOP
LT8619/LT8619-5
22
Rev. B
For more information www.analog.com
Figure13. Case Temperature Rise vs Load Current Figure14. Case Temperature Rise vs Ambient Temperature
For higher ambient temperatures, care should be taken in
the layout of the PCB to ensure good heat sinking of the
LT8619. The exposed pad on the bottom of the package
must be soldered to a ground plane. This ground should
be tied to large copper layers below with thermal vias;
these layers will spread heat dissipated by the LT8619.
Placing additional vias can reduce thermal resistance fur-
ther. Figure13 shows the rise in case temperature vs load
current. Note that a higher ambient temperature will result
in bigger case temperature rise as shown in Figure14.
Power dissipation within the LT8619 can be estimated
by calculating the total power loss from an efficiency
measurement and subtracting the inductor loss. The
die temperature is calculated by multiplying the LT8619
power dissipation by the thermal resistance from junction
to ambient.
Figure15 shows the typical derating maximum output
current curve. As with any monolithic switching regu-
lator, the PCB layout, thermal resistance, air flow, other
heat sources in the vicinity affect how efficiently heat can
be removed from the die and radically change the die
junction temperature. The actual LT8619 switcher output
voltage and current sourcing capability might deviate from
the performance curve stated in this data sheet. When
pushing the LT8619 to its limit, verify its operation in the
actual environment. AT HIGH AMBIENT TEMPERATURE,
CONTINUOUS OPERATION ABOVE THE MAXIMUM
OPERATION JUNCTION TEMPERATURE MAY IMPAIR
DEVICE RELIABILITY OR PERMANENTLY DAMAGE THE
DEVICE.
Figure15. LT8619 Derating Maximum Output
Current with Junction Temperature Less Than 125°C
APPLICATIONS INFORMATION
V
= 12V
V
OUT
= 5V
f
SW
= 700kHz
T
A
= 25°C
FORCED CONTINUOUS MODE
LOAD CURRENT (A)
0
0.2
0.4
0.6
0.8
1.0
1.2
0
5
10
15
20
CASE TEMPERATURE RISE (°C)
8619 F13
V
= 12V
V
OUT
= 5V, 1.2A LOAD
f
SW
= 700kHz
CONTINUOUS OPERATION ABOVE
MAXIMUM JUNCTION TEMPERATURE
MAY PERMANENTLY DAMAGE THE DEVICE
AMBIENT TEMPERATURE (°C)
25
50
75
100
125
0
5
10
15
20
25
30
35
CASE TEMPERATURE RISE (°C)
8619 F14
V
= 12V
V
OUT
= 3.3V
T
J(MAX)
≤ 125°C
FORCED CONTINUOUS MODE
AMBIENT TEMPERATURE (°C)
90
95
100
105
110
115
120
125
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
MAXIMUM OUTPUT CURRENT (A)
8619 F15
f
SW
= 700kHz
f
SW
= 2MHz
LT8619/LT8619-5
23
Rev. B
For more information www.analog.com
3.3V 400kHz Step-Down Converter
15µH
PG
100k
1M
316k
121k
0.1µF
22µF
8619 TA02
V
OUT
3.3V
1.2A
BST
SW
PG
BIAS
FB
GNDSYNC
RT
6.8pF
L = VISHAY IHLP-3232CZ-11
COUT
= TDK C3225X7R1C226K250
fOSC = 400kHz
OFF ON
1µF
2.2µF
V
IN
4V TO 60V
INTVCC
VIN
EN/UV
LT8619
1.8V 2MHz Step-Down Converter
LT8619 2.2µH
PG PG
100k
1.87M
1.5M
20k
OFF ON
0.1µF
22µF
5.6pF
8619 TA03
1µF
2.2µF
V
IN
3.3V TO 12V
V
OUT
1.8V
1.2A
BST
SW
INTVCC
VIN
GNDSYNC
EN/UV
RT
L = VISHAY IHLP-2020AB-01
C
OUT
= TDK C3225X7R1C226K250
FB
BIAS
fOSC = 2MHz
TYPICAL APPLICATIONS
LT8619/LT8619-5
24
Rev. B
For more information www.analog.com
TYPICAL APPLICATIONS
5V 2MHz Step-Down Converter
12V 700kHz Step-Down Converter
LT8619-5 4.7µH
20k
0.1µF
22µF
8619 TA04
V
IN
6V TO 36V
(60V TRANSIENT)
V
OUT
5V
1.2A
BST
SW
GNDSYNC
RT
BIAS
OUT
OFF ON
1µF
2.2µF
INTVCC
VIN
EN/UV
PG PG
100k
L = VISHAY IHLP-2020BZ-01
COUT = TDK C3225X7R1C226K250
fOSC = 2MHz
LT8619 22µH
PG PG
100k
0.931M 401k
66.5k
66.5k
OFF ON
0.1µF
10µF
×2
22pF
8619 TA05
1µF
2.2µF
V
IN
13V TO 60V
V
OUT
12V
1.2A
BST
SW
INTVCC
VIN
GNDSYNC
EN/UV
RT FB
BIAS
L = VISHAY IHLP-2020CZ-11
C
OUT
= MURATA GRM32ER7YA106K
fOSC = 700kHz
LT8619/LT8619-5
25
Rev. B
For more information www.analog.com
PACKAGE DESCRIPTION
3.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
0.40 ±0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ±0.10
(2 SIDES)
0.75 ±0.05
R = 0.125
TYP
2.38 ±0.10
(2 SIDES)
15
106
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DD) DFN REV C 0310
0.25 ±0.05
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ±0.05
(2 SIDES)2.15 ±0.05
0.50
BSC
0.70 ±0.05
3.55 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
LT8619/LT8619-5
26
Rev. B
For more information www.analog.com
PACKAGE DESCRIPTION
MSOP (MSE16) 0213 REV F
0.53 ±0.152
(.021 ±.006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.17 –0.27
(.007 – .011)
TYP
0.86
(.034)
REF
0.50
(.0197)
BSC
16
16151413121110
12345678
9
9
18
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL
NOT EXCEED 0.254mm (.010") PER SIDE.
0.254
(.010) 0° – 6° TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
5.10
(.201)
MIN
3.20 – 3.45
(.126 – .136)
0.889 ±0.127
(.035 ±.005)
RECOMMENDED SOLDER PAD LAYOUT
0.305 ±0.038
(.0120 ±.0015)
TYP
0.50
(.0197)
BSC
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 ±0.102
(.112 ±.004)
2.845 ±0.102
(.112 ±.004)
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
1.651 ±0.102
(.065 ±.004)
1.651 ±0.102
(.065 ±.004)
0.1016 ±0.0508
(.004 ±.002)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
0.280 ±0.076
(.011 ±.003)
REF
4.90 ±0.152
(.193 ±.006)
DETAIL “B”
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
0.12 REF
0.35
REF
MSE Package
16-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1667 Rev F)
LT8619/LT8619-5
27
Rev. B
For more information www.analog.com
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
A 07/18 Clarified SYNC Threshold Units
Clarified Efficiency at VOUT = 5V
3
5
B 10/19 Clarified Conditions on VIN Quiescent Current at No Load and In Regulation
Added Note 5 to Feedback Voltage Line Regulation
Added Note 5
3
3
4
LT8619/LT8619-5
28
Rev. B
For more information www.analog.com
ANALOG DEVICES, INC. 2018–2019
10/19
www.analog.com
RELATED PARTS
TYPICAL APPLICATION
PART DESCRIPTION COMMENTS
LT8602 42V, Quad Output (2.5A + 1.5A + 1.5A + 1.5A) 95% Efficiency,
2.2MHz Synchronous Micropower Step-Down DC/DC
Converter with IQ = 25μA
VIN(MIN) = 3V, VIN(MAX) = 42V, VOUT(MIN) = 0.8V, IQ = 2.5μA,
ISD<1μA, 6mm × 6mm QFN-40
LT8609/LT8609A 42V, 2A, 94% Efficiency, 2.2MHz Synchronous Micropower
Step-Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3V, VIN(MAX) = 42V, VOUT(MIN) = 0.8V, IQ = 2.5μA,
ISD<1μA, MSOP-10E
LT8610 42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, MSOP-16E
LT8610A/LT8610AB 42V, 3.5A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, MSOP-16E
LT8610AC 42V, 3.5A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3V, VIN(MAX) = 42V, VOUT(MIN) = 0.8V, IQ = 2.5μA,
ISD<1μA, MSOP-16E
LT8611 42V, 2.5A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with IQ = 2.5μA and Input/Output
Current Limit/Monitor
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, 3mm × 5mm QFN-24
LT8612 42V, 6A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step-Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 3.0μA,
ISD < 1μA, 3mm × 6mm QFN-28
LT8613 42V, 6A, 96% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with Current Limiting
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 3.0μA,
ISD < 1μA, 3mm × 6mm QFN-28
LT8614 42V, 4A, 96% Efficiency, 2.2MHz Synchronous Silent Switcher
Step- Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, 3mm × 4mm QFN-18
LT8616 42V, Dual 2.5A + 1.5A, 95% Efficiency, 2.2MHz Synchronous
Micropower Step-Down DC/DC Converter with IQ = 5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.8V, IQ = 5μA, ISD<
1μA, TSSOP-28E, 3mm × 6mm QFN-28
LT8620 65V, 2.5A, 94% Efficiency, 2.2MHz Synchronous Micropower
Step- Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 65V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, MSOP-16E, 3mm × 5mm QFN-24
LT8640/LT8640-1 42V, 5A, 96% Efficiency, 3MHz Synchronous Micropower
Step-Down DC/DC Converter with IQ = 2.5μA
VIN(MIN) = 3.4V, VIN(MAX) = 42V, VOUT(MIN) = 0.97V, IQ = 2.5μA,
ISD < 1μA, 3mm × 4mm QFN-18
Ultralow EMI 5V 2MHz Step-Down Converter
LT8619-5 4.7µH
L
IN
4.7µH
FB1
BEAD
20k
0.1µF
22µF
8619 TA06
4.7µF
VIN
6V TO 36V
(60V TRANSIENT)
V
OUT
5V
1.2A
BST
SW
PG
BIAS
OUT
GNDSYNC
RT
4.7µF4.7µF
PG
100k
OFF ON
1µF
INTVCC
VIN
EN/UV
FB1 = TDK MPZ2012S221A
LIN = XFL4020
L = VISHAY IHLP-2020BZ-01
COUT = TDK C3225X7R1C226K250
fOSC = 2MHz