2007-2012 Microchip Technology Inc. DS22042B-page 1
MCP1603/B/L
Features
• Over 90% Typical Efficiency
• Output Current Up To 500 mA
• Low PFM Quiescent Current = 45 µA, typical
(MCP1603/L)
• Low Shutdown Current = 0.1 µA, typical
• Adjustable Output Voltage:
- 0.8V to 4.5V
• Fixed Output Voltage:
- 1.2V, 1.5V, 1.8V, 2.5V, 3.3V (MCP1603/L)
- 1.8V, 3.3V (MCP1603B)
• 2.0 MHz Fixed-Frequency PWM (Heavy Load)
• Automatic PWM-to-PFM Mode Transition
(MCP1603/L)
• PWM Mode Only Option (MCP1603B)
• 100% Duty Cycle Operation
• Intern all y Co mp ens ated
• Undervoltage Lockout (UVLO)
• Overtemperature Protection
• Space Saving Packages:
- 5-Lead TSOT , Two Pinout Types (MCP1603/L)
- 8-Lead 2 x 3 DFN
Applications
• Cellu lar Telephones
• Portable Computers
•Organizers / PDAs
• USB Powered Devices
•Digital Cameras
• Port ab le Equi pm ent
• +5V or +3.3V Distributed Systems
• Headsets
General Description
The MCP1603/B/L is a high-efficiency, fully-integrated
500 mA synchronous buck regulator whose 2.7V to
5.5V input voltage range makes it ideally suited for
applications powered from 1-cell Li-Ion or 2-cell/3-cell
NiMH/NiCd batteries.
At heavy loads, the MCP1603/B/L operates in the
2.0 MHz fixed frequency pulse-width modulation
(PWM) mode, which provides a low noise, low-output
ripple, sm all-s ize sol ution. Wh en the load is reduce d to
light levels, the MCP1603/L automatically changes
operation to a Pulse Frequency Modulation (PFM)
mode to minimize quiescent current draw from the
battery. No intervention is necessary for a smooth
transiti on fr om one mode t o anoth er. These t wo mo des
of operation allow the MCP1603/L to achieve the
highest efficiency over the entire operating current
range.
The MCP1603B device disables the PFM mode
switching, and operates only in normal PWM mode
over the entire load range (without skipping).
MCP1603B is for applications that cannot tolerate the
low-frequency output ripple associated with PFM
switching.
The MCP1603/B/L family is available with either an
adjustable or fixed-output voltage. The available fixed
output voltage options for MCP1603/L are 1.2V, 1.5V,
1.8V, 2.5V and 3.3V, and for MCP1603B are 1.8 and
3.3V. Whe n a fixed option is use d, only three add itional
small external components are needed to form a
complete solution. Couple this with the low profile,
small-foot print packages and the entire system
solution is achieved with minimal size.
Additional protection features include: UVLO,
overtemperature and overcurrent protection.
2.0 MHz, 500 mA Synchronous Buck Regulator
MCP1603/B/L
DS22042B-page 2 2007-2012 Microchip Technology Inc.
Package Types
Typical Application Circuit
1
2
34
5LX
VFB/VOUT
SHDN
GND
VIN 1
2
34
5
LX
VFB/VOUT
SHDN
GND
VIN
MCP1603/MCP1603B
TSOT MCP1603L
TSOT MCP1603
2x3 DFN*
SHDN
NC
VFB/VOUT
VIN
NC
1
2
3
4
8
7
6
5NC
GNDLX
* Includes Exposed Thermal Pad (EP); see Table 3-1.
EP
9
VIN
SHDN
GND
VFB
LX
VIN
2.7V to 4.5V VOUT
1.8V @ 500 mA
COUT
4.7 µF
CIN
4.7 µF
L1
4.7 µH
30
40
50
60
70
80
90
100
Efficiency (%)
VOUT = 1.8V VIN = 2.7V
VIN = 3.6V VIN = 4.5V
10
20
30
0.1 1 10 100 1000
Output Current (mA)
__ PFM/PWM (MCP1603/L)
--- PWM (MCP1603B)
2007-2012 Microchip Technology Inc. DS22042B-page 3
MCP1603/B/L
Functional Block Diagram
ILIMPWM
ILIMPFM
IPEAKPWM
IPEAKPFM
VIN
SHDN
VFB /V
OUT
GND
LX
Band
Gap
UVLO
Switch Drive
UVLO
VREF
Logic and Timing
S
RQ
Q
Soft Start
VREF
PWM/PFM
Logic
VREF
Slope
Comp. OSC
-IPK Limit
UVLO
Thermal
Shutdown
TSD
EA
POFF NOFF
PWM/PF M - PWM ONLY
TSD
PFM Error Amp
PWM Error Amp
OV Threshold
UV Threshold
IPK Limit
-ILPK
IPEAKPWM
IPEAKPFM
Disable
Switcher
-ILPK
PWM-ONLY
+
+
MCP1603/B/L
DS22042B-page 4 2007-2012 Microchip Technology Inc.
NOTES:
2007-2012 Microchip Technology Inc. DS22042B-page 5
MCP1603/B/L
1.0 ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings †
VIN - GND... ...... ...... ....... ...... ...... ...... ....... ...... ..................+6.0V
All Other I/O...............................(GND - 0.3V) to (VIN + 0.3V)
LX to GND.............................................. -0.3V to (VIN + 0.3V)
Output Sh o rt Circuit Cur r e n t ......... ............. ...... .....Con tinuous
Power Dissipation (Note 5)............. .............Internally Limite d
Storage Temperature .......... .... .. .. .... ....... .. .. ...-65°C to +150°C
Ambient Temp. with Power Applied ................-40°C to +85°C
Operating Junction Temperature...................-40°C to +125°C
ESD Protection On All Pins:
HBM .............................................................................4 kV
MM ..............................................................................300V
† Notice: S tresses above those listed und er "Maximum
Ratings" may cause permanent damage to the device.
This is a stress rating only and functional operation of
the devi ce at those or any other c onditions ab ove those
indicated in the operational sections of this specifica-
tion is not intended. Exposure to maximum rating con-
ditions for extended periods may affect device
reliability.
DC CHARACTERISTICS
Electrical Charac teris tics: Unless otherwise indicated, MCP1603/L, VIN = SHDN = 3.6V, COUT = CIN = 4.7 µF,
L = 4.7 µH, VOUT(ADJ) = 1.8V, IOUT =100mA, T
A = +25°C. Boldface speci fication s apply over the T A rang e of -40°C
to +85°C.
Parameters Sym Min Typ Max Units Conditions
Input Characteristics
Input Voltage VIN 2.7 —5.5 VNote 1
Maximum Output Current IOUT 500 ——mANote 1
Shutdown Current IIN_SHDN — 0.1 1 µA SHDN = GND
Quiescent Current - PFM IQ—4560 µA SHDN = VIN, IOUT = 0 mA,
device switching
Quiescent Current - PWM IQ1.0 2.7 4 mA SHDN = VIN, IOUT = 0 mA,
device switching (MCP1603B)
Shutdown/UVLO/Thermal Shutdown Characteristics
SHDN, Logic Input Voltage Low VIL ——15 %VIN VIN = 2.7V to 5.5V
SHDN, Logic Input Voltage High VIH 45 ——%V
IN VIN = 2.7V to 5.5V
SHDN, Input Leakage Current IL_SHDN -1.0 ±0.1 1.0 µA VIN = 2.7V to 5.5V
Undervoltage Lockout UVLO 2.12 2.28 2.43 VV
IN Falling
Undervoltage Lockout Hysteresis UVLOHYS —140—mV
Thermal Shutdown TSHD —150— °CNote 4, Note 5
Thermal Shutdown Hysteresis TSHD-HYS —10—°CNote 4, Note 5
Note 1: The input voltage should be greater then the output voltage plus headroom voltage; higher load currents
increase the input voltage required for regulation. MCP1603B device requires a minimum load for
regulation. See Section 2.0, Typical Performance Curves for typical operating voltage ranges.
2: Reference Feedback Voltage Tolerance applies to adjustable output voltage setting.
3: VR is the output voltage setting.
4: The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable
temperature and the thermal resistance from junction to air (i.e. TA, TJ, JA). Exceeding the maximum
allowable power di ssipation causes the device to initiate thermal shutdown.
5: The internal MOSFET switches have an integral diode from the LX pin to the VIN pin, and from the LX pin
to the GND pin. In cases where these diodes are forward-biased, the package power dissipation limits
must be adhered to. Thermal protection is not able to limit the junction temperature for these cases.
6: The current limit threshold is a cycle-by-cycle peak current limit.
MCP1603/B/L
DS22042B-page 6 2007-2012 Microchip Technology Inc.
Output Characteristics
Adjustable Output Voltage Range VOUT 0.8 —4.5 VNote 2
Reference Feedback Voltage VFB —0.8— V
Reference Feedback Voltage
Tolerance -3.0 — +3.0 % TA = -40°C to +25°C
-2.5 — +2.5 % TA = +25°C to +85°C
Feedbac k Inpu t Bias C urren t IVFB —0.1—nA
Output Voltage Tolerance Fixed VOUT -3.0% VR+3.0% % TA = -40°C to +25°C, Note 3
VOUT -2.5 VR+2.5 % TA = +25°C to +85°C, Note 3
Line Regulation VLINE-REG —0.3—%/VV
IN = V R+ 1V to 5.5V,
IOUT = 100 mA
Load Regulation VLOAD-REG —0.35— %V
IN =V
R+1.5V,
ILOAD =100mAto500mA
Internal Os ci llator Frequen cy FOSC 1.5 2.0 2.8 MHz
Start Up Time TSS —0.6—msT
R= 10% to 90%
RDSon P-Channel RDSon-P —500—mIP=100mA
RDSon N-Channel R DSon-N —500—mIN= 100 mA
LX Pin Leakage Current ILX -1.0 ±0.1 1.0 µA SHDN =0V, V
IN =5.5V,
LX=0V, L
X=5.5V
Positive Current Limit Threshold +ILX(MAX) —860—mANote 6
TEMPERATURE SPECIFICATIONS
Electrical Specifications: Unless otherwise indicated, all limits are specified for: VIN + 2.7V to 5.5V
Parameters Sym Min Typ Max Units Conditions
Temperature Ranges
Operati ng Junction Te mp erat ure Ra ng e TJ-40 — +125 °C Steady State
Storage Temperature Range TA-65 — +150 °C
Maximum Junct ion Temperature TJ— — +150 °C Transient
Package Thermal Resistances
Thermal Resistance, 5L-TSOT JA — 207.4 — °C/W Typical 4-layer Board with
Internal Ground Plane
Thermal Resistance, 8L-2x3 DFN JA — 68 — °C/W Typical 4-layer Board with
Internal Gro und Plane and
2-Vias in Thermal Pad
DC CHARACTERISTICS (CONTINUE D)
Electrical Charac teris tics: Unless otherwise indicated, MCP1603/L, VIN = SHDN = 3.6V, COUT = CIN = 4.7 µF,
L = 4.7 µH, VOUT(ADJ) = 1.8V, IOUT =100mA, T
A = +25°C. Boldface speci fication s apply over the T A rang e of -40°C
to +85°C.
Parameters Sym Min Typ Max Units Conditions
Note 1: The input voltage should be greater then the output voltage plus headroom voltage; higher load currents
increase the input voltage required for regulation. MCP1603B device requires a minimum load for
regulation. See Section 2.0, Typical Performance Curves for typical operating voltage ranges.
2: Reference Feedback Voltage Tolerance applies to adjustable output voltage setting.
3: VR is the output voltage setting.
4: The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable
temperature and the thermal resistance from junction to air (i.e. TA, TJ, JA). Exceeding the maximum
allowable power di ssipation causes the device to initiate thermal shutdown.
5: The internal MOSFET switches have an integral diode from the LX pin to the VIN pin, and from the LX pin
to the GND pin. In cases where these diodes are forward-biased, the package power dissipation limits
must be adhered to. Thermal protection is not able to limit the junction temperature for these cases.
6: The current limit threshold is a cycle-by-cycle peak current limit.
2007-2012 Microchip Technology Inc. DS22042B-page 7
MCP1603/B/L
2.0 TYPICAL PERFORMANCE CURVES
Note: Unless otherwise indicated, MCP1603/L, VIN = SHDN =3.6V, C
OUT =C
IN = 4.7 µF, L = 4.7 µH,
VOUT(ADJ) = 1.8V, ILOAD = 100 mA, T A= +25°C. Adj ustable or f ixed output vo ltage optio ns can be used to ge nerate the
Typical Performance Characteristics.
FIGURE 2-1: PFM IQ vs. Ambient
Temperature (MCP1603/L).
FIGURE 2-2: PWM IQ vs. Ambient
Temperature (MCP1603B).
FIGURE 2-3: Efficiency vs. Input Voltage
(VOUT = 1.2V).
FIGURE 2-4: PFM IQ vs. Input Voltage
(MCP1603/L).
FIGURE 2-5: PWM IQ vs. Input Voltage
(MCP1603B).
FIGURE 2-6: Efficiency vs. Output Load
(VOUT = 1.2V).
Note: The gra phs and table s pro vi ded follo w ing this note are a statistical sum ma ry ba se d on a li mited numb er of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
42
43
44
45
46
47
48
49
50
e
scent Current (µA)
VOUT = 1.8V
VIN = 4.2V
V
=30V
VIN = 3.6V
40
41
42
-40 -25 -10 5 20 35 50 65 80 95 110 125
Qui
e
Ambient Temperature (oC)
V
IN
=3
.
0V
2.7
2.8
2.9
3
3.1
3.2
3.3
s
cent Current (mA)
V
OUT
= 1.8V
V
IN
= 3.0V
V
IN
=
3.6V
V
IN
= 4.2V
2.4
2.5
2.6
2.7
-40-25-105 2035506580
Quie
s
Ambient Temperature (oC)
V
IN
3.6V
70
75
80
85
90
95
100
Efficiency (%)
VOUT = 1.2V
IOUT = 100 mA
IOUT = 500 mA
IOUT = 300 mA
60
65
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Input Voltage (V)
44
46
48
50
52
i
escent Current (µA)
TA= +25oC
TA= +90oC
40
42
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Qu
i
Input Voltage (V)
TA= -40oC
2.6
2.8
3
3.2
3.4
s
cent Current (mA)
TA= +25oC
TA= +90oC
VOUT = 1.8V
2
2.2
2.4
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Quie
s
Input Voltage (V)
TA= -40oC
30
40
50
60
70
80
90
100
E
fficiency (%)
V
OUT
= 1.2
V
VIN = 2.7V
VIN = 3.6V
0
10
20
30
0.1 1 10 100 1000
E
Output Current (mA)
OUT
VIN = 4.2V PFM/PWM
PWM Only
MCP1603/B/L
DS22042B-page 8 2007-2012 Microchip Technology Inc.
Note: Unless otherwise indicated, MCP1603/L, VIN = SHDN =3.6V, C
OUT =C
IN = 4.7 µF, L = 4.7 µH,
VOUT(ADJ) = 1.8V, ILOAD = 100 mA, T A= +25°C. Adjus table or fixe d output volt age optio ns can be used to ge nerate the
Typical Performance Characteristics.
FIGURE 2-7: Efficiency vs. Input Voltage
(VOUT = 1.8V).
FIGURE 2-8: Effi ciency vs. Output Load
(VOUT = 1.8V).
FIGURE 2-9: Efficiency vs. Input Voltage
(VOUT = 2.4V).
FIGURE 2-10: Line Regulation vs. Ambient
Temperature (VOUT = 1.8V).
FIGURE 2-11: Output Voltage vs. Load
Current (VOUT = 1.8V).
FIGURE 2-12: PFM/PWM Effi c ien cy vs.
Output Load (VOUT = 2.4V ).
80
85
90
95
100
Efficiency (%)
VOUT = 1.8V
IOUT = 100 mA
IOUT = 500 mA
IOUT = 300 mA
70
75
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Input Voltage (V)
30
40
50
60
70
80
90
100
E
fficiency (%)
V
18V
VIN = 4.2V
VIN = 2.7V
VIN = 3.6V
0
10
20
30
0.1 1 10 100 1000
E
Output Current (mA)
V
OUT =
1
.
8V
PFM/PWM
PWM Only
80
85
90
95
100
Efficiency (%)
VOUT = 2.4V
IOUT = 100 mA
IOUT = 500 mA
IOUT = 300 mA
75
80
33.544.555.5
Input Voltage (V)
02
0.3
0.4
0.5
0.6
n
e Regualtion (%/V)
IOUT = 100 mA
IOUT = 300 mA
VOUT = 1.8V
0.1
0
.
2
-40 -25 -10 5 20 35 50 65 80 95 110 125
Li
n
Ambient Temperature (
o
C)
1.76
1.77
1.78
1.79
1.80
1.81
1.82
O
utput Voltage (V)
TA= +125oC
TA= -40oC
TA= +25oC
TA= +90oC
1.74
1.75
100 150 200 250 300 350 400 450 500
O
Output Current (mA)
30
40
50
60
70
80
90
100
E
fficiency (%)
V
24V
VIN = 4.2V
VIN = 2.7V
VIN = 3.6V
0
10
20
30
0.1 1 10 100 1000
E
Output Current (mA)
V
OUT =
2
.
4V
PFM/PWM
PWM Only
2007-2012 Microchip Technology Inc. DS22042B-page 9
MCP1603/B/L
Note: Unless otherwise indicated, MCP1603/L, VIN = SHDN =3.6V, C
OUT =C
IN = 4.7 µF, L = 4.7 µH,
VOUT(ADJ) = 1.8V, ILOAD = 100 mA, T A= +25°C. Adj ustable or f ixed output vo ltage optio ns can be used to ge nerate the
Typical Performance Characteristics.
FIGURE 2-13: Efficiency vs. Input Voltage
(VOUT = 3.3V).
FIGURE 2-14: Efficiency vs. Output Load
(VOUT = 3.3V).
FIGURE 2-15: PWM-O nly De vice Mini mum
Load for Regulation (MCP1603B).
FIGURE 2-16: Switching Frequency vs.
Ambient Temp er atu re.
FIGURE 2-17: Switching Frequency vs.
Input Voltage.
FIGURE 2-18: Switch Resistance vs. Input
Voltage.
90.0
92.5
95.0
97.5
100.0
Efficiency (%)
VOUT = 3.3V
IOUT = 100 mA
IOUT = 500 mA
IOUT = 300 mA
85.0
87.5
3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5
Input Voltage (V)
40
50
60
70
80
90
100
E
fficiency (%)
VIN = 4.2V
VIN = 3.6V
0
10
20
30
0.1 1 10 100 1000
E
Output Current (mA)
V
OUT = 3.3
V
PFM/PWM
PWM Only
3
4
5
6
7
8
9
10
o
ad Current (mA)
TA= -40oC
TA= +25oC
T
A
=+85
o
C
Regulation
0
1
2
3
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
L
o
VIN -V
OUT (V)
T
A
= +85
C
No Regulation
2.05
2.10
2.15
2.20
h
ing Frequency (MHz)
1.95
2.00
-40 -25 -10 5 20 35 50 65 80 95 110 125
Switc
h
Ambient Temperature (
o
C)
200
2.05
2.10
2.15
2.20
h
ing Frequency (MHz)
1.95
2
.
00
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Switc
h
Input Voltage (V)
0.45
0.50
0.55
0.60
0.65
tch Resistance ()
N-Channel
P-Channel
0.35
0.40
2.7 3.05 3.4 3.75 4.1 4.45 4.8 5.15 5.5
Swit
Input Voltage (V)
MCP1603/B/L
DS22042B-page 10 2007-2012 Microchip Technology Inc.
Note: Unless otherwise indicated, MCP1603/L, VIN = SHDN =3.6V, C
OUT =C
IN = 4.7 µF, L = 4.7 µH,
VOUT(ADJ) = 1.8V, ILOAD = 100 mA, T A= +25°C. Adjus table or fixe d output volt age optio ns can be used to ge nerate the
Typical Performance Characteristics.
FIGURE 2-19: Switch Resistance vs.
Ambient Temperature.
FIGURE 2-20: Output Voltage Startup
Waveform.
FIGURE 2-21: Heavy Load Switching
Waveform.
FIGURE 2-22: PFM Light Load Switching
Wav eforms (MCP1603/L).
FIGURE 2-23: Output Voltage Load Step
Response vs. Time.
FIGURE 2-24: Output Voltage Line Step
Response vs. Time.
0.5
0.6
0.7
0.8
0.9
tch Resistance ()
N-Channel
0.3
0.4
-40 -25 -10 5 20 35 50 65 80 95 110 125
Swit
Ambient Temperature (oC)
P-Channel
2007-2012 Microchip Technology Inc. DS22042B-page 11
MCP1603/B/L
Note: Unless otherwise indicated, MCP1603/L, VIN = SHDN =3.6V, C
OUT =C
IN = 4.7 µF, L = 4.7 µH,
VOUT(ADJ) = 1.8V, ILOAD = 100 mA, T A= +25°C. Adj ustable or f ixed output vo ltage optio ns can be used to ge nerate the
Typical Performance Characteristics.
FIGURE 2-25: PWM Light Load Switc hin g
Wav eforms ( MCP1603B).
IL=20mA/div
VLx =2V/div
IOUT =5mA
0.4 µs/div
VOUT =50mV/div, AC
MCP1603/B/L
DS22042B-page 12 2007-2012 Microchip Technology Inc.
NOTES:
2007-2012 Microchip Technology Inc. DS22042B-page 13
MCP1603/B/L
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
3.1 Power Supply Input Voltage Pin
(VIN)
Connect the input voltage source to VIN. The input
source must be decoupled to GND with a 4.7 µF
capacitor.
3.2 Ground Pin (GND)
Ground p in fo r the dev ic e. Th e lo op a r ea o f the g roun d
traces should be kept as minimal as possible.
3.3 Shutdown Contr ol Input Pin
(SHDN)
The SHDN pin is a logic-level input used to enable or
disable the device. A logic high (>45% of VIN) will
enable the regulator output. A logic low (<15% of VIN)
will ensure that the regulator is disabled.
3.4 Feedback / Output Voltage Pin
(VFB/VOUT)
For adjus table outp ut options, c onnect the cente r of the
output voltage divider to the VFB/VOUT pin. For fixed-
output voltage options, connect the output directly to
the VFB/VOUT pin .
3.5 Switch Node, Buck Inductor
Connection Pin (LX)
Connect the LX pin directly to the buck inductor. This
pin carries large signal-level current; all connections
should be made as short as possible.
3.6 Exposed Metal Pad (EP)
For the DFN package, connect the Exposed Pad to
GND, with vias in to the GN D plane . This con nec tio n to
the GND plane will aid in heat removal from the
package.
TABLE 3-1: PIN FUNCTION TABLE
MCP1603/B
TSOT-23 MCP1603L
TSOT-23 MCP1603
2x3 DFN Symbol Description
147V
IN Power Supply Input Voltage Pin
2 2 8 GND Ground Pin
3 1 3 SHDN Shutdown Control Input Pin
454V
FB/VOUT Feedback / Output Voltage Pin
531L
XSwitch Node, Buck Inductor Connection Pin
— — 2, 5, 6 NC No C onne c t
— — Exposed
Pad EP For the DFN package, the center exposed pad is a thermal
path to remove heat from the device. Electrically, this pad is
at ground potential and should be connected to GND.
MCP1603/B/L
DS22042B-page 14 2007-2012 Microchip Technology Inc.
NOTES:
2007-2012 Microchip Technology Inc. DS22042B-page 15
MCP1603/B/L
4.0 DETAILED DESCRIPTION
4.1 Device Overview
The MCP1603/L is a synchronous buck regulator that
operates in a Pulse Frequency Modulation (PFM)
mode or a Pulse Width Modulation (PWM) mode to
maximize system efficiency over the entire operating
current range. Capable of operating from a 2.7V to
5.5V input voltage source, the MCP1603 can deliver
500 mA of continuous output curre nt.
The MCP1603B device disables the PFM mode
switching, and operates only in normal PWM mode.
When using the MCP1603/B/L, the PCB area required
for a c omplete step-down conve rter is m inimized, since
both the main P-Channel MOSFET and the synchro-
nous N- Channe l MO SFET are integra ted. Al so w hile in
PWM mode, the device switches at a constant
frequency of 2.0 MHz (typical), which allows for small
filtering components. Both fixed and adjustable output
volt age optio ns are av ailable. The fixed volta ge opt ions
(1.2V, 1.5 V 1.8 V, 2.5V, 3.3V) do not re quire an externa l
voltage divider, which further reduces the required
circuit board footprint. The adjustable output voltage
options allow for more flexibility in the design, but
require an external voltage divider.
Additionally, the device features an undervoltage lock-
out (UVLO), overtemperature shutdown, overcurrent
protection and enable/disable control.
4.2 Synchronous Buck Regulator
The MCP1603/L has two distinct modes of operation
that allow the device to maintain a high level of
efficiency throughout the entire operating current and
voltage range. The device automatically switches
between PWM mode and PFM mode, depending on
the output load requirements. MCP1603B switches in
PWM mode only.
4.2.1 PFM/PWM MODE DEVICE OPTION
(MCP1603/L)
During heavy load conditions, the MCP1603/L
operates at a high, fixed switching frequency of
2.0 MHz (typical) using current mode control. This
minimizes output ripple (10 – 15 mV, typically) and
noise, while maintaining high efficiency (88% typical
with VIN =3.6V, V
OUT =1.8V, I
OUT = 300 mA).
During normal PWM operation, the beginning of a
switching cycle occurs when the internal P-Channel
MOSFET is turned on. The ramping ind uc tor cu rren t is
sensed and tie d to o ne i nput of the internal high-speed
comparator. The other input to the high-speed
comparator is the error amplifier output. This is the
difference betwe en the internal 0.8V reference and the
divide d-dow n output volt age. Wh en the se nsed c urrent
becomes equal to the amplified error signal, the high-
speed comparator switches states and the P-Channel
MOSFET is turned off. The N-Channel MOSFET is
turned on until the inter nal oscilla tor sets an internal RS
latch, initiating the beginning of another switching
cycle.
PFM-to-PWM mode transition is initiated for any of the
following conditions:
• Continuous devi ce switching
• Output voltage has dropped out of regulation
4.2.1.1 Light Load, PFM Mode
During light-load conditions, the MCP1603/L operates
in a PFM mode. When the MCP1603/L enters this
mode, it beg ins to skip puls es to minimiz e unnecessar y
quiescent-current draw by reducing the number of
switchin g cycl es per s econd. T he typic al quie scent c ur-
rent draw for this device is 45 µA.
PWM-to-PFM mode transition is initiated for any of the
following conditions:
• Disconti nu ous i ndu cto r current is s en se d f or a s et
duration
• Inductor peak current fal ls bel ow the trans iti on
threshold limit
4.2.2 PWM MODE DEVICE OPTION
(MCP1603B)
There are applications that cannot tolerate the low
frequency pulse skipping mode or the output ripple
voltage associated with it, which is distinctive for PFM
switching.
The MCP1603B device has disabled the PFM mode
switching. It operates only in normal PWM mode over
the entire load range (without skipping pulses). During
periods of light load operation, the MCP1603B
continues to operate at a constant 2 MHz switching
frequenc y, keeping the output ri pple v olt age low er tha n
PFM mode. Because there are no skipping pulses, a
minimum load current is necessary to keep output in
regulation (see Figure 2-15, without a minimum load,
the output voltage will be greater than the set point).
The minimum load value depends on the input-to-
output ratio.
MCP1603/B/L
DS22042B-page 16 2007-2012 Microchip Technology Inc.
4.3 Soft Start
The output of the MCP1603 is controlled during start-
up. This control allows for a very minimal amount of
VOUT overshoot during start-up from VIN rising above
the UVLO voltage or SHDN being enabled.
4.4 Overtemperature Protection
Overtemperature protection circuitry is integrated in the
MCP1603/B/ L devic e famil y. This circuitry mo nitors the
device junc tio n te mp erature and sh ut s the dev ice off, if
the junction temperature exceeds the typical +150°C
threshold. If this threshold is exceeded, the device will
automatically restart once the junction temperature
drops by approximately 10°C. The soft start is reset
during an over temperture condition.
4.5 Overcurrent Protecti on
Cycle-by-cycle current limiting is used to protect the
MCP1603/B/L device family from being damaged when
an external short circuit is applied. The typical peak
current limit is 860 mA. If the sensed current reaches
the 860 mA limi t, the P-Channel MOSFET is t urned of f,
even if the output voltage is not in regulation. The
device will attempt to start a new switching cycle when
the internal oscillator sets the internal RS latch.
4.6 Enable/Disable Control
The SHDN pin is used to enable or disable the
MCP1603/B/L. When the SHDN pin is pulled low, the
device is disabled. When pulled high, the device is
enabled and begins operati on, unless the inp ut voltag e
is below the UVLO threshold or a fa ult condition exist s.
4.7 Undervoltage Lockout (UVLO)
The UVLO feature uses a comparator to sense the
input voltage (VIN) level. If the input voltage is lower
than the voltage necessary to properly operate the
MCP1603, the UVLO feature will hold the con verter off.
When VIN rises above the necessary input voltage, the
UVLO is released and soft start begins. Hysteresis is
built into the UVLO circuit to compensate for input
impedance. For example, if there is any resistance
betwee n the inp ut v ol tage so urc e an d the dev ic e whe n
it is operating, there will be a voltage drop at the input
to the device equal to IIN xR
IN. The typical hysteresis
is 14 0 mV.
2007-2012 Microchip Technology Inc. DS22042B-page 17
MCP1603/B/L
5.0 APPLICATION INFORMATION
5.1 Typical Applications
The MCP1603/B/L 500 mA synchronous buck
regulator operates over a wide input voltage range
(2.7V to 5.5V) and is ide al f or s ingle-c el l L i-Io n ba ttery-
powered applications, USB-powered applications,
three cell NiMH or NiCd applications and 3V or 5V
regulated input applications. The 5-lead TSOT and 8-
lead 2 x 3 DFN pac kages prov ide a sm all footp rin t with
minimal ex ternal components.
5.2 Fixed Output Voltage Applications
The Typical Application Circuit shows a fixed
MCP1603/B/L in an application used to convert three
NiMH batteries into a well-regulated 1.8V @ 500 mA
output. A 4.7 µF input capacitor, 4.7 µF output
capacitor, and a 4.7 µH inductor make up the entire
external component solution for this application. No
external voltage divider or compensation is necessary.
In addition to the fixed 1.8V option, the MCP1603 is
also available in 1.2V, 1.5V, 2.5V, or 3.3V fixed voltage
options.
5.3 Adjustable Output Voltage
Applications
When the desired output for a particular application is
not covered by the fixed-voltage options, an adjustable
MCP1603/B/L can be used. The circuit listed in
Figure 6-2 shows an adjustable device being used to
convert a 5V rail to 1.0V @ 500 mA. T he output voltage
is adjustable by using two external resistors as a volt-
age divider. For adjustable-output voltages, it is
recommended that the top resistor divider value be
200 k. The bottom resistor value can be calculated
using the following equation:
EQUATION 5-1:
For adjustable output applications, an additional R-C
compensation network is necessary for control loop
stability. Recommended values for any output voltage
are:
Refer to Figure 6-2 for proper placem ent of R COMP and
CCOMP.
5.4 Input Cap acitor Selection
The input current to a buck converter, when operating
in Continuous Conduction mode, is a squarewave with
a duty cycle defined by the output voltage (VOUT) to
input v ol t ag e (VIN) relatio nship of VOUT/VIN. To prevent
undesirable input voltage transients, the input capacitor
should be a low-ESR type with an RMS current rating
given by Equation 5.5. Because of their small size and
low ES R, cerami c capacito rs are oft en used. C eramic
material X5R or X7 R are w el l s uit ed, si nc e th ey ha ve a
low-temperature coefficient and acceptable ESR.
EQUATION 5-2:
Table 5-1 contains the recommend range for the input
capa ci tor val ue.
5.5 Output Capacitor Selection
The output capacitor helps provide a stable output
voltage during sudden load transients, smooths the
current that flows from the inductor to the load, and
reduces the output voltage ripple. Therefore, low-ESR
capacitors are a desirable choice for the output capac-
itor. As with the input capacitor, X5R and X7R ceramic
capacitors are well suited for this application.
The output ripple voltage is often a design specifica-
tion. A buck converters’ output ripple voltage is a
function of the charging and discharging of the output
capacitor and the ESR of the capacitor. This ripple
voltage can be calculated by Equation 5-3.
EQUATION 5-3:
Table 5-1 cont ains the recomm end range for the o utput
capa ci tor val ue.
RBOT RTOP VFB
VOUT VFB
–
-----------------------------
=
Example:
RTOP =200k
VOUT =1.0V
VFB =0.8V
RBOT =200k x (0.8V/(1.0V – 0.8V))
RBOT =800k(Standard Value = 787 k)
RCOMP =4.99k
CCOMP =33pF
TABLE 5-1: CAPACITOR VALUE RANGE
CIN COUT
Minimum 4.7 µF 4.7 µF
Maximum — 22 µF
ICIN RMS,IOUT MAX,VOUT VIN VOUT
–
VIN
------------------------------------------------------
=
VOUT
ILESR
IL
8fC
---------------------+=
MCP1603/B/L
DS22042B-page 18 2007-2012 Microchip Technology Inc.
5.6 Inductor Selection
When using the MCP1603, the inductance value can
range from 3.3 µH to 10 µH. An inductance value of
4.7 µH is recommended to achieve a good balance
between converter load transient response and
minimized noise.
The value of inductance is selected to achieve a
desired amount of ripple current. It is reasonable to
assume a ripple current that is 20% of the maximum
load current. The larger the amount of ripple current
allow ed, the lar ger the output c ap acito r value beco mes
to meet ripple voltage specifications. The inductor
ripple current can be calculated according to the
following equation.
EQUATION 5-4:
When considering inductor ratings, the maximum DC
current rating of t he induc tor shoul d be at l east equ al to
the maximum load current, plus one half the peak-to-
peak inductor ripple current (1/2 x IL). The inductor
DC resistance adds to the total converter power loss.
An inductor with a low DC resistance allows for higher
converter efficiency.
5.7 Thermal Calculations
The MCP1603 is available in two different packages
(TSOT-23 and 2x3 DFN). The junction temperature is
estimated by calculating the power dissipation and
applying the package thermal resistance (JA). The
maximum continuous junction temperature rating for
the MCP1603 is +125°C.
To quickly estimate the internal power dissipation for
the switching buck regulator, an empirical calculation
using measured efficiency can be used. Given the
measured efficiency, the internal power dissipation is
estimated by the following equation:
EQUATION 5-5:
The difference between the first term, input power
dissipation, and the second term, power delivered, is
the internal power dissipation. This is an estimate
assuming that most of the power lost is internal to the
MCP1603. There is some percentage of power lost in
the buck inductor, with very little loss in the input and
output capacitor s.
TABLE 5-2: MCP1603 RECOMMENDED
INDUCTORS
Part
Number Value
(µH)
DCR
(max)
ISAT
(A) Size
WxLxH (mm)
Coiltronics®
SD3110 3.3 0.195 0.81 3.1x3.1x1.0
SD3110 4.7 0.285 0.68 3.1x3.1x1.0
SD3110 6.8 0.346 0.58 3.1x3.1x1.0
SD3812 3.3 0.159 1.40 3.8x3.8x1.2
SD3812 4.7 0.256 1.13 3.8x3.8x1.2
SD3812 6.8 0.299 0.95 3.8x3.8x1.2
Würth Elektronik®
WE-TPC
Type XS 3.3 0.225 0.72 3.3x3.5x0.95
WE-TPC
Type XS 4.7 0.290 0.50 3.3x3.5x0.95
WE-TPC
Type S 4.7 0.105 0.90 3.8x3.8x1.65
WE-TPC
Type S 6.8 0.156 0.75 3.8x3.8x1.65
WE-TPC
Type T iny 4.7 0.100 1.7 2.8x2.8x2.8
ILVOUT
FSW L
------------------- 1 VOUT
VIN
-------------–
=
Where:
FSW = Switching Frequency
Sumida®
CMD4D06 3.3 0.174 0.77 3.5x4.3x0.8
CMD4D06 4.7 0.216 0.75 3.5x4.3x0.8
CMD4D06 6.8 0.296 0.62 3.5x4.3x0.8
Coilcraft®
XFL3012-
332ME_ 3.3 0.106 1.2 3x3x1.2
XFL3012-
472ME_ 4.7 0.143 1.0 3x3x1.2
LPS4018-
103ML_ 10 0.200 1.2 4x4x1.8
TDK-EPC®
B82462_
G4472M 4.7 0.04 1.8 6x6x3
VLS3015E
T-4R7M 4.7 0.113 1.1 3x3x1.5
TABLE 5-2: MCP1603 RECOMMENDED
INDUCTORS (CONTINUED)
Part
Number Value
(µH)
DCR
(max)
ISAT
(A) Size
WxLxH (mm)
VOUT IOUT
Efficiency
-------------------------------------
VOUT IOUT
–PDiss
=
2007-2012 Microchip Technology Inc. DS22042B-page 19
MCP1603/B/L
5.8 PCB Layout Information
Good printed circuit board layout techniques are
important to any switching circuitry, and switching
power supplies are no different. When wiring the high-
current paths, short and wide traces should be used.
This hig h-current p ath is show n with red c onnectio ns in
Figure 5-1. The current in this path is switching.
Therefore , it is important that the component s along the
high-current path should be placed as close as possi-
ble to the MCP1603 to minimize the loop area.
The feedback resistors and feedback signal should be
routed aw ay from the switching node and this s witching
current l oop. W hen po ssib le, ground plane s and tra ces
should be used to help shield the feedback signal and
minimize noise and magnetic interference.
FIGURE 5-1: PCB High Current Path.
VIN
SHDN
GND
VFB
LX
VIN
2.7V to 4.5V VOUT
1.8V @ 500 mA
COUT
4.7 µF
CIN
4.7 µF
L1
4.7 µH
MCP1603/B/L
DS22042B-page 20 2007-2012 Microchip Technology Inc.
NOTES:
2007-2012 Microchip Technology Inc. DS22042B-page 21
MCP1603/B/L
6.0 TYPICAL APPLICATION CIRCUITS
l
FIGURE 6-1: Single Li-Ion to 1.5V @ 500 mA Application.
FIGURE 6-2: 5V to 1.0V @ 500 mA Application.
FIGURE 6-3: Three NiMH Batteries to 1.2V @ 500 mA Application.
VIN
SHDN
GND
VFB
LX
VIN
3.0V to 4.2V VOUT
1.5V @ 500 mA
COUT
4.7 µF
CIN
4.7 µF
L1
4.7 µH
RTOP
200 k
RBOT
787 k
VIN
SHDN
GNDVFB
LX
VIN
5.0V VOUT
1.0V @ 500 mA
COUT
4.7 µF
CIN
4.7 µF
L1
4.7 µH
RCOMP
4.99 kCCOMP
33 pF
VIN
SHDN
GND
VFB
LX
VIN
2.7V to 4.5V VOUT
1.2V @ 500 mA
COUT
4.7 µF
CIN
4.7 µF
L1
4.7 µH
MCP1603/B/L
DS22042B-page 22 2007-2012 Microchip Technology Inc.
NOTES: