MIC23158/9
3MHz PWM Dual 2A Buck Regulato r with
HyperLight Load
and Power Good
HyperLight Load is a registered trademark of Micrel, Inc.
MLF and MicroLeadFrame are registered trademarks Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
November 2012
M9999-110812-A
General Description
The MIC23158/9 is a high-efficiency, 3MHz, dual, 2A
synchronous buck regulator with HyperLight Load mode,
power good output indicator, and programmable soft start.
The MIC23159 also provides an auto discharge feature
that switches in a 225Ω pull down circuit on its output to
discharge the output capacitor when disabled. HyperLight
Load provides very high efficiency at light loads and ultra-
fast transient response which makes the MIC23158/9
perfectly suited for supplying processor core voltages. An
additiona l b enef it of th is pro pr ietary arch itect ure is very low
output ripple voltage throughout the entire load range with
the use of s mall output ca p ac itor s. The 20-pin 3mm x 4mm
MLF® package saves precious board space and requires
seven external components for each channel.
The MIC23158/9 is designed for use with a very small
inductor, down to 0.47µH, and an output capacitor as small
as 2.2µF that enables a total so lution size, less than 1mm
in height.
The MIC23158/9 has a v ery low quiesc ent curr ent of 45µA
and achieves a peak efficiency of 94% in continuous
conduction mode. In discontinuous conduction mode, the
MIC23158/9 can achieve 83% efficiency at 1mA.
The MIC23158/9 is avail able in a 20-pin 3mm x 4mm MLF
package with an operating junction temperature range
from –40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• 2.7V to 5.5V input voltage
• Adjustab le output voltage (down to 1.0V)
• 2 independent 2A out puts
• Up to 94% peak efficiency
• 83% typ ic al eff ic iency at 1m A
• 2 independent power good indicators
• Independent programmable soft start
• 45µA typical quiescent current
• 3MHz PWM operation in continuous conduction mode
• Ultra-fast transient response
• Fully-integrated MOSFET switches
• Output pre-bias safe
• 0.1µA shutdown current
• Thermal-shutdown and current-limit protection
• 20-pin 3mm x 4mm MLF package
• Internal 225Ω pull-down circuit on output (MIC23159)
• –40°C to +125°C junction temperature range
Applications
• Solid State Drives (SSD)
• Smart phones
• Tablet PCs
• Mobile handsets
• Portable devices (PMP, PND, UMPC, GPS)
• WiFi/WiMax/WiBro applications
_______________________________________________________________________________________________________
Typical Appli cation
Micrel Inc.
MIC23158/9
Ordering Information
Part Number Nominal Output Voltage Output
Auto
Discharge Junction Temperature Range Package
VOUT1 VOUT2
MIC23158YML ADJ ADJ NO –40°C to +125°C 20-Pin 3mm x 4mm MLF
MIC23159YML ADJ ADJ YES –40°C to +125°C 20-Pin 3mm x 4mm MLF
Notes:
1. Fixed output voltage options available. Contact Micrel Marketing for details.
2. MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
1
1
2
3
4
5
6
16
15
14
13
12
11
7 8 10
9
20 19 1718
EP
VIN1
SW2
SW1
PGND1
PGND2
VIN2
AVIN2
AGND2
EN2
SNS2
FB2
PG2
SS2
SS1
PG1
FB1
AVIN1
AGND1
EN1
SNS1
3mm x 4mm MLF (ML) Adjustable Output Voltage
(Top View)
Pin Description
Pin Number
(Adjustable) Pin Name Pin Function
1 VIN1 Power Input Voltage for Regulator 1. C onn ect a capacitor to ground to decouple noise and switching
transients.
2 PGND1 Power Ground for Regul ator 1.
3 SW1 Switch (Output): Internal power MOSFET output switches for regulator 1.
4 SW2 Switch (Output): Internal power MOSFET output switches for regulator 2.
5 PGND2 Power Ground for Regul ator 2.
6 VIN2 Power Input Voltage for Regulator 2. Connect a capacitor to ground to decouple noise and switching
transients.
7 AVIN2 Analog Input Voltage for Regulator 2. Tie to VIN2 and connect a capacitor to ground to decouple
noise.
Micrel Inc.
MIC23158/9
Pin Description (Continued)
Pin Number
(Adjustable) Pin Name Pin Function
8 AGND2 Analog Ground for Regulator 2. Connect to a central ground point where all high current paths meet
(CIN, COUT, PGND2) for best operation.
9 EN2 Enable Input for Regulator 2. Logic high enables operation of regulator 2. Logic low will shut down
regulator 2. Do not leave floating.
10 SNS2 Sense Input for Regulator 2. Connect to the output of regulator 2 as close to the output capacitor as
possible to accurately sense the output voltage.
11 FB2 Feedback Input for Regulator 2. Connect a resistor divider from the output of regulator 2 to ground to
set the output voltage.
12 PG2 Power Good Output for Regulator 2. Open drain output for the power good indicator for output 2. Use
a pull-up resistor between this pin and VOUT2 to indicate a power good condition.
13 SS2 Soft-Start for Regulator 2. C on nect a minimum of 200pF capacitor to ground to set the turn-on time of
regulator 2. Do not leave floating.
14 SS1 Soft-Start fo r Regulator 1. Connect a minimum of 200pF capacitor to ground to set the turn-on time of
regulator 1. Do not leave floating.
15 PG1 Power Good Output for Regulator 1. Open drain output for the power good indicator for output 1. Use
a pull-up resistor between this pin and VOUT1 to indicate a power good condition.
16 FB1 Feedback Input for Regulator 1. Connect a resistor divider from the output of regulator 1 to ground to
set the output voltage.
17 SNS1 Sense Input for Regulator 1. Connect to the output of regulator 1 as close to the output capacitor as
possible to accurately sense the output voltage.
18 EN1 Enable Input for Regulator 1. Logic high enables operation of regulator 1. Logic low will shut down
regulator 1. Do not leave floating.
19 AGND1 Analog Ground for Regulator 1. Connect to a central ground point where all high current paths meet
(CIN, COUT, PGND1) for best operation.
20 AVIN1 Analog Input Voltage for Regulator 1. Tie to VIN1 and connect a capacitor to ground to decouple
noise.
EP ePad Exposed Heat Sink Pad. Connect to PGND.
Micrel Inc.
MIC23158/9
Absolute Maximum Ratings(1)
Supply Voltage (AVIN1, AVIN2, VIN1, VIN2) .... −0.3V to 6V
Switch1 (VSW1), Sense1 (VSNS1) ...................... −0.3V to VIN1
Enable1 (VEN1), Power Good1 (VPG1) ............. −0.3V to VIN1
Feedback1 (VFB1) ......................................... −-0.3V to VIN1
Switch2 (VSW2), Sense2 (VSNS2) ...................... -0.3V to VIN2
Enable2 (VEN2), Power G ood2 (VPG2) ............. −0.3V to VIN2
Feedback2 (VFB2) ........................................... −0.3V to VIN2
Power Dissipation TA = 70°C .................... Inter na lly Limited
Storage Temperature Range .................... −65°C to +150°C
Lead Temperature (soldering, 10s) ............................ 260°C
ESD Rating(3) .................................................. ESD sensitive
Operating Ratings(2)
Supply Voltage (AVIN1, VIN1) ..................... +2.7V to +5.5V
Supply Voltage (AVIN2, VIN2) ..................... +2.7V to +5.5V
Enable Input Voltage (VEN1, VEN2) ...................... 0V to VIN1,2
Output Voltage Range (VSNS1, VSNS2) .......... +1.0V to +3.3V
Junction Temperature Range (TJ) ...... −40°C ≤ TJ ≤ +125°C
Thermal Resistance
3mm x 4mm MLF-20 (θJA) ................................. 53°C/W
Electrical Characteristics(4)
TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified.
Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
Typ.
Max.
Units
Supply Voltage Range 2.7 5.5 V
Undervoltage Lockout Threshold Rising 2.45 2.55 2.65 V
Undervoltage Lockout Hysteresis
75
mV
Quiescent Current IOUT = 0mA , SNS > 1.2 * VOUTNOM (both outputs) 45 90 µA
Shutdown Current VEN = 0V; VIN = 5.5V (per output) 0.1 5 µA
Feedback Regulation Voltage IOUT = 20mA 0.6045 0.62 0.6355 V
Feedback Bias Current (per output) 0.01 µA
Current Limit SNS = 0.9*VOUTNOM 2.2 4.3 A
Output Voltage Line Regulation
VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, IOUT = 20mA
0.45 %/V
VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, IOUT = 20mA
Output Voltage Load Regulation
DCM, VIN = 3.6V if VOUTNOM < 2.5V 0.55
%
DCM, VIN = 5.0V if VOUTNOM ≥ 2.5V 1.0
CCM, VIN = 3.6V if VOUTNOM < 2.5V
0.8
CCM, VIN = 5.0V if VOUTNOM ≥ 2.5V
PWM S witch RDSON ISW1,2 = 100mA PMOS
ISW1,2 = -100mA NMOS 0.20
0.19 Ω
Switching Frequency IOUT = 180mA 3 MHz
Soft-Start Time VOUT = 90%, CSS = 470pF 300 µs
Soft-Start Current VSS = 0V 2.7 µA
Power Good Threshold (Rising) 86 92 96 %
Power Good Threshold Hysteresis 7 %
Power Good Delay Time Rising 68 µs
Power Good Pull-Down Resistance 95 Ω
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to functi on outside its operati ng rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4. Specific at i on for packaged product only.
Micrel Inc.
MIC23158/9
Electrical Characteristics(4) (Continued)
TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified.
Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter Condition Min. Typ. Max. Units
Enable Input Voltage Logic Low
0.4
V
Logic High
1.2
Enable Input Current 0.1 2 µA
Output Discharge Resistance MIC23159 Only; EN = 0V, IOUT = 250µA 225 Ω
Overtemperature Shutdown 160 °C
Shutdown Hysteresis 20 °C
Micrel Inc.
MIC23158/9
Typical Characteris tics
Eff iciency (V OUT = 3. 3V ) vs.
Output C urrent
0
10
20
30
40
50
60
70
80
90
100
110 100 1000 10000
O UT PUT CURRE NT (mA)
EFFI CIENCY ( %)
VIN = 4. 2V
V IN = 5V
C
OUT
=4.7µF
L=1µH
Eff iciency (V OUT = 2. 5V ) vs.
Output C urrent
0
10
20
30
40
50
60
70
80
90
100
110 100 1000 10000
O UT PUT CURRE NT (mA)
EFFI CIENCY ( %)
VIN = 4. 2V
VIN = 3. 6V
V IN = 5V
C
OUT
=4.7µF
L=1µH
Eff iciency (V OUT = 1. 8V ) vs.
Output C urrent
0
10
20
30
40
50
60
70
80
90
100
110 100 1000 10000
O UT PUT CURRE NT (mA)
EFFI CIENCY (% )
VIN = 2. 7V
VIN = 4. 2V
VIN = 3. 6V
V IN = 5V
COUT=4.7µF
L=1µH
Efficiency (V
OUT
= 1.5V) vs.
Output Current
0
10
20
30
40
50
60
70
80
90
100
110 100 1000 10000
O UT PUT CURRE NT (mA)
EFFI CIENCY (% )
VIN = 2. 7V
VIN = 4. 2V
VIN = 3. 6V
V IN = 5V
C
OUT
=4.7µF
L=1µH
V
OUT
Rise Time
vs. C
SS
10
100
1000
10000
100000
1000000
100 1000 10000 100000 1000000
CSS (pF)
RI SE TIME (µs)
V
OUT
= 1.8V
C
OUT
= 4.7
µF
Current Limi t
vs. Input Voltage
0.0
1.0
2.0
3.0
4.0
5.0
6.0
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
CURRENT LIMII T (A)
V
OUT
= 1.8V
C
OUT
= 4.7
µF
Quiescent Cu rrent
vs. Input Voltage
20
25
30
35
40
45
50
55
60
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
Q UIESCENT CURRE NT (µA)
No Swi t chi ng
SNS > V
OUTNOM
* 1. 2
C
OUT
= 4. 7µF
T = 125°C
T = -40°C
T = 25°C
Shut dow n Current
vs. Input Voltage
1
10
100
1000
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
SHUTDOWN CURRENT (nA)
Li ne Regulat ion
(CCM)
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
O UTPUT VOLTAG E ( V)
I
OUT
= 1A
I
OUT
= 300m A
V
OUTNOM
= 1. 8V
C
OUT
= 4. 7µF
Micrel Inc.
MIC23158/9
Typical Characteristics (Continued)
Li ne Regulat ion
(HLL)
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
O UTPUT VOLTAG E ( V)
I
OUT
= 20m A
I
OUT
= 80m A
I
OUT
= 1m A
V
OUTNOM
= 1. 8V
C
OUT
= 4. 7µF
Load Regulation
(CCM)
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
200 600 1000 1400 1800
O UT PUT CURRE NT (mA)
O UTPUT VOLTAG E ( V)
VIN = 3. 6V
VOUTNOM = 1.8V
COUT = 4.7µF
Load Regulation
(HLL)
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
020 40 60 80 100 120
O UT PUT CURRE NT (mA)
O UTPUT VOLTAG E ( V)
V
IN
= 3. 6V
V
OUTNOM
=1.8V
C
OUT
= 4. 7µF
V
OUTMAX
vs. V
IN
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
2.5 3.0 3.5 4.0 4.5 5.0 5.5
I NPUT VOLTA GE (V)
O UTPUT VOLTAG E ( V)
I
OUT
= 400mA
I
OUT
= 1.2A
I
OUT
= 100mA
T
A
= 25°C
Feedback Voltage
vs. Temperature
0.59
0.60
0.61
0.62
0.63
0.64
0.65
-40 -20 020 40 60 80 100 120
TEM PERATURE (°C)
FEEDBACK V OLTAG E ( V )
V
IN
= 3. 6V
V
OUT
= 1. 8V
Switching Frequency
vs. Temperature
0
1
2
3
4
5
-40 -20 020 40 60 80 100 120
TEM PERATURE (°C)
SWITCHING FREQUENCY ( MHz)
V
IN
= 3. 6V
V
OUTNOM
= 1. 8V
C
OUT
= 4. 7µF
Micrel Inc.
MIC23158/9
Functional Characteristics
Micrel Inc.
MIC23158/9
Functional Characteristics (Continued)
Micrel Inc.
MIC23158/9
Functional Characteristics (Continued)
Micrel Inc.
MIC23158/9
Functional Diagram
Figure 1. Simplified MIC23158 Functional Block Diagram – Adjustable Output Voltage
Micrel Inc.
MIC23158/9
Functional Diagrams (Continued)
Figure 2. Simplified MIC23159 Functional Block Diagram – Adjustable Output Voltage
Micrel Inc.
MIC23158/9
Functional Description
VIN
The input supply (VIN) provides power to the internal
MOSFETs for the switch mode regulator section. The
VIN operating range is 2.7V to 5.5V. An input capacitor
with a minimum voltage rating of 6.3V is recommended.
Due to the high switching speed, a minimum 2.2µF
bypass capacitor placed close to VIN and the power
ground (PG ND) pin is r equired. Ref er to the PC B Layout
Recommendations for details.
AVIN
Analog VI N (A VIN) pro vides power to the interna l cont rol
and analog supply circuitry. AVIN and VIN must be tied
together. Careful layout should be considered to ensure
high frequency switching noise caused by VIN is
reduced before r eachi ng A VIN. A 1µF c apac itor as clo se
to AVIN as possible is recommended. Refer to the PCB
Layout Recom men dat io ns for details.
EN
A logic hig h si gnal on t he e nable pin acti vates the out put
voltage of the device. A logic low signal on the enable
pin deacti vates the output and red uces suppl y current to
0.1µA. Do not leave the EN pin floating. W hen disabled,
the MIC2 315 9 switches i n a 22 5Ω loa d f rom the SN S pin
to AGND, to discharge the output capacitor.
SW
The switch (SW) connects directly to one end of the
inductor and provides the current path during switching
cycles. T he other en d of the in ductor is connected to the
load, SNS pin, and output capacitor. Due to the high
speed switching on this pin, the switch node should be
routed away from sensitive nodes whenever possible.
SNS
The sense (SNS) pin is connected to the output of the
device to provide feedback to the control circuitry. The
SNS connection should be placed close to the output
capacitor. Ref er to th e la yout rec omm endatio ns f or m ore
details. The SNS pin also provides the output active
discharge circuit path to pull down the output voltage
when the device is dis ab led .
AGND
The analog ground (AGND) is the ground path for the
biasing and control circuitry. The current loop for the
signal grou nd s ho ul d be separate f r om the power gr ou nd
(PGND) loop. Refer to the PCB Layout
Recommendations for details.
PGND
The power ground pin is the ground path for the high
current in PWM mode. The current loop for the power
ground should be as small as possible and separate
from the analog ground (AGND) loop as applicable.
Refer to the layout recommendations for more details.
PG
The power good (PG) pin is an open drain output which
indicates when the output voltage is within regulation.
This is indicated by a logic high signal when the output
voltage is above the PG threshold. Connect a pull up
resistor greater than 5kΩ from PG to VOUT.
SS
An external soft start circuitry set by a capacitor on the
SS pin reduces inrush current and prevents the output
voltage from overshooting at start up. T he SS pin is used
to control the output voltage ramp up time and the
approximate equation for the ramp time in milliseconds
is 296 x 103 x ln(10) x CSS. For example, for a CSS =
470pF, TRISE ≈ 300µs. Refer to the “VOUT Rise Time vs.
CSS” graph in the Typical Characteristics section. The
minimum recommended value for CSS is 200pF.
FB
The feedback (FB) pin is provided for the adjustable
voltage option. This is the control input for setting the
output volta ge. A resis tor divider networ k is c onnected to
this pin from the output and is compared to the internal
0.62V reference within the regulation loop.
The output voltage can be calculated using Equation 1:
+⋅= R2
R1
1VV
REF
OUT
Eq. 1
Recommended feedback resistor values:
VOUT R1 R2
1.2V 274k 294k
1.5V 316k 221k
1.8V 301k 158k
2.5V 324k 107k
3.3V 309k 71.5k
Micrel Inc.
MIC23158/9
Application Information
The MIC23158/9 is a high-performance DC/DC step
down regu lator offer ing a sm all solution size. Supporting
two outputs of up to 2A each in a 3mm x 4mm MLF
package. Using the HyperLight Load switching scheme,
the MIC23158/9 is able to maintain high efficiency
throughout the entire load range while providing ultra
fast load transient response. The following sections
provide addit ion al de vice appl icati on inf or mation.
Input Capacitor
A 2.2µF ceramic capacitor or greater should be placed
close to the VIN pin and PGND pin for bypassing. A
Murata GRM188R60J475KE19D, size 0603, 4.7µF
ceramic capacitor is recommended based upon
performance, size and cost. A X5R or X7R temperature
rating is recommended for the input capacitor.
Output Capacitor
The MIC23158/9 is designed for use with a 2.2µF or
greater ceramic output capacitor. Increasing the output
capacitance will lower output ripple and improve load
transient response but could also increase solution size
or cost. A low equivalent series resistance (ESR)
ceramic output capacitor such as the Murata
GRM188R60J475KE19D, size 0603, 4.7µF ceramic
capacitor is recommended based upon performance,
size and cost. Both the X7R or X5R temperature rating
capacitors are recommended.
Inductor Selection
When selecting an inductor, it is important to consider
the following factors:
• Inductance
• Rated current value
• Size requirements
• DC resistance (DCR)
The MIC23158/9 is designed for use with a 0.47µH to
2.2µH inductor. For faster transient response, a 0.47µH
inductor will yield the best result. F or lower o utput rippl e,
a 2.2µH inductor is recommended.
Maximum current ratings of the inductor are generally
given in two methods; permissible DC current, and
saturation current. Permissible DC current can be rated
either for a 40°C temperature rise or a 10% to 20% loss
in inductance. Ensure the inductor selected can handle
the max imum operating c urrent. When saturation cur re nt
is specified, make sure that there is enough margin so
that the peak current does not cause the inductor to
saturate.
Peak current can be calculated in Equation 2:
×
×
−
+
=L
f2 /VV
1
V
II IN
OUT
OUT
OUTPEAK
Eq. 2
As shown by the calculation above, the peak inductor
current is inversely proportional to the switching
frequency and the inductance. The lower the switching
frequenc y or inducta nce, th e higher the peak current. As
input voltage increases, the peak current also increases.
The size of the inductor de pends on the requ irements of
the application. Refer to the typical application circuit
and Bill o f Ma teria ls for details.
Figure 3. Transition between CCM Mode to HLL Mode
DC resistance (DCR) is also important. While DCR is
inversely proportional to size, DCR can represent a
significant efficiency loss. Refer to the “Efficiency
Considerations” subsection.
The transition between continuous conduction mode
(CCM) to HyperLight Load mode is determined by the
inductor ripple current and the load current.
The diagram shows the sig nals f or high-side switch drive
(HSD) for TON control, the Inductor current, and the low-
side switch drive (LSD) for TOFF control.
In HLL mode, the inductor is charged with a fixed TON
pulse on the high side switch. After this, the low side
switch is turned o n a nd c urrent f alls at a rate V OUT/L. The
controller remains in HLL m ode while the induct or falling
current is detec ted to cross approximatel y -5 0m A. When
the LSD (or TOFF) time reaches its minimum and the
inductor falling current is no longer able to reach the
threshold, the part is in CCM mode.
Micrel Inc.
MIC23158/9
Once in CCM mode, the TOFF time will not vary.
Theref or e, it is im por tant to note th at if L is large e nou g h,
the HLL transition level will not be triggered.
That inductor is illustrated in Figure 3:
50mA2
135nsV
LOUT
MAX −
−
=
Eq. 3
Du ty Cycle
The typical maximum duty cycle of the MIC23158/9 is
80%.
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power supplied.
100
IV I
V
%Efficiency ININ
OUTOUT ×
×
×
=
Eq. 4
There are two types of losses in switching converters;
DC losses and switching losses. DC losses are simply
the power dissipation of I2R. Power is dissipated in the
high side s witch during the on cycle. Po wer loss is equal
to the high side MOSFET RDSON m ultiplied b y the switch
current squared. During the off cycle, the low side N-
channel MOSFET conducts, also dissipating power.
Device operating current also reduces efficiency. The
product of the quiescent (operating) current and the
supply voltage represents another DC loss. The current
required dr iving the gates on and off at a constant 3MHz
frequency and the switching transitions make up the
switching losses.
Efficien cy (VOUT = 1.8V) vs.
Output Current
0
10
20
30
40
50
60
70
80
90
100
110 100 1000 10000
O UT PUT CURRENT (m A)
EFFICIENCY ( %)
V IN = 2. 7V
V IN = 4. 2V
V IN = 3. 6V
VIN = 5V
C
OUT
=4.7µF
L=1µH
Figure 4. Efficiency under Load
Figure 4 shows an efficiency curve. From 1mA load to
2A, eff icienc y losses are do m inated b y quiesc ent curr ent
losses, gate drive and transition losses. By using the
HyperLight Load mode, the MIC23158/9 is able to
maintain high efficiency at low output currents.
Over 180mA, efficiency loss is dominated by MOSFET
RDSON and inductor losses. Higher input supply voltages
will increase the gate-to-so urce threshold on the inter nal
MOSFETs, thereby reducing the internal RDSON. This
impr oves efficienc y by reducing DC l osses in the de vice.
All but the inductor losses are inherent to the device. In
which case, inductor selection becomes increasingly
critical in efficiency calculations. As the inductors are
reduced in size, the DC resistance (DCR) can become
quite significant. The DCR losses can be calculated as in
Equation 5:
PDCR = IOUT2 x DCR Eq. 5
From that, the loss in efficiency due to inductor
resistance can be calculated as in Equation 6:
100
PIV IV
1LossEfficiency DCROUTOUT
OUTOUT ×
+×
×
−=
Eq. 6
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade off between efficiency and
size in this case.
HyperLight Load Mode
The MIC23158/9 uses a minimum on and off time
proprietary control loop (patented by Micrel). When the
output voltage falls below the regulation threshold, the
error comparator begins a switching cycle that turns the
PMOS on and keeps it on for the duration of the
minimum-on-time. This increases the output voltage. If
the output voltage is over the regulation threshold, then
the error com parator turns the PMO S off for a minim um-
off-time until the output drops below the threshold. The
NMOS acts as an ideal rectifier that conducts when the
PMOS is off. Using an NMOS switch instead of a diode
allows f or lo wer vol tag e dro p ac r oss the s witc h ing de vic e
when it is on. The synchronous switching combination
between the PMOS and the NMOS allows the control
loop to work in discontinuous mode for light load
operations. In discontinuous mode, the MIC23158/9
works in HyperLight Load to regulate the output. As the
output current increases, the off time decreases, thus
provides more energy to the output. This switching
scheme improves the efficiency of MIC23158/9 during
light load currents by only switching when it is needed.
Micrel Inc.
MIC23158/9
As the load c urrent incr eases, the MIC23158/9 g oes into
continuous conduction mode (CCM) and switches at a
frequency centered at 3MHz. The equation to calculate
the load when the MIC23158/9 goes into continuous
conduction mode may be approximated by the following
formula:
×
×−
>f2L D)V(V
IOUTIN
LOAD
Eq. 7
As shown in Equation 7, the load at which the
MIC23158/9 transitions from HyperLight Load mode to
PWM mode is a function of the input voltage (VIN), output
voltage (VOUT), duty cycle (D), inductance (L) and
frequency (f). As shown in Figure 5, as the output
current increases, the switching frequency also
increases until the MIC23158/9 goes from HyperLight
Load mode to PW M m ode at approxim ately 180mA. The
MIC23158/9 will s witc h at a r elativel y constant f reque nc y
around 3MHz once the output current is over 180mA.
Switching Frequency
vs. Output Current
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0.1 110 100 1000 10000
O UT PUT CURRENT (m A)
SWITCHING FRE QUENCY ( MHz)
L=1.0µH
L=0.47µH
Figure 5. SW Frequency vs. Output Current
Micrel Inc.
MIC23158/9
Typical Application Circuit (Adjustable Output)
Bill of Materials
Item
Part Name
Manufacturer
Description
Qty.
C1, C2
06036D105KAT2A
AVX (1)
1µF, 0603, 6.3V 2
GRM188R60J105KA01D
Murata (2)
C1608X5R0J105K
TDK (3)
C3, C4, C5, C6
06036D475KAT2A
AVX
4.7µF, 6.3V, X5R, 0603 4
GRM188R60J475KE19D
Murata
C1608X5R0J475K
TDK
C7, C8
06035A471JAT2A
AVX
470pF, 50V, 0603 2
GRM1885C1H471JA01D
Murata
C1608C0G1H471J
TDK
L1, L2
CDRH4D28CLDNP-1R0P
SUMIDA (4)
1µH, 3.0A, 14mΩ, L5.1mm x W5.1mm x H3.0mm
2
LQH44PN1R0NJ0
MURATA
1µH, 2.8A, 14mΩ, L5.1mm x W5.1mm x H3.0mm
R1
CRCW06033013FKEA
Vishay/Dale (5)
301KΩ, 1%, 1/10W, 0603
1
R2
CRCW06031583FKEA
Vishay/Dale
158KΩ, 1%, 1/10W, 0603
1
R3
CRCW06033163FKEA
Vishay/Dale
316KΩ, 1%, 1/10W, 0603
1
R4
CRCW06032213FKEA
Vishay/Dale
221KΩ, 1%, 1/10W, 0603
1
R5, R6
CRCW06031003FKEA
Vishay/Dale
100KΩ, 1%, 1/10W, 0603
2
R7, R8
CRCW06031002FKEA
Vishay/Dale
10KΩ, 1%, 1/10W, 0603
2
U1 MIC23158/9YML Micrel, Inc (6)
3MHz PWM Dual 2A Buck Regulator with HyperLight
Load and Power Good
1
Notes:
1. AVX: www.avx.com.
2. Murata: www.murata.com.
3. TDK: www.tdk.com.
4. Sumi da: www.sumida.com.
5. Vishay/Dale: www.vishay.com.
6. Micrel, Inc.: www.micrel.com.
Micrel Inc.
MIC23158/9
PCB Layout Recommendations
Top Layer
Bottom Layer
Micrel Inc.
MIC23158/9
Package Information(1)
20-Pin 3mm x 4mm MLF
Note:
1. Package i nformat i on is correct as of the publication date. For updates and most current inform ati on, go t o www.micrel.com.
Micrel Inc.
MIC23158/9
Recommended Land Pattern
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informat i on is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
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lant
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