MCP1642B/D
1.8A Input Current Switch, 1 MHz Low-Voltage Start-Up
Synchronous Boost Regulator
Features
General Description
• Up to 96% Typical Efficiency
• 1.8A Typical Peak Input Current Limit:
- IOUT > 175 mA @ 1.2V VIN, 3.3V VOUT
- IOUT > 600 mA @ 2.4V VIN, 3.3V VOUT
- IOUT > 800 mA @ 3.3V VIN, 5.0V VOUT
- IOUT > 1A @ VIN > 3.6V, 5.0V VOUT
• Low Start-Up Voltage: 0.65V, typical 3.3V VOUT
@ 1 mA
• Low Operating Input Voltage: 0.35V, typical 3.3V
VOUT @ 1 mA
• Output Voltage Range:
- Reference Voltage, VFB = 1.21V
- 1.8V to 5.5V for the adjustable device option
- 1.8V, 3.0V, 3.3V and 5.0V for fixed VOUT
options
• Maximum Input Voltage VOUT < 5.5V
• PWM Operation: 1 MHz
- Low Noise, Anti-Ringing Control
• Power Good Open-Drain Output
• Internal Synchronous Rectifier
• Internal Compensation
• Inrush Current Limiting and Internal Soft-Start
• Selectable, Logic-Controlled Shutdown States:
- True Load Disconnect Option (MCP1642B)
- Input-to-Output Bypass Option (MCP1642D)
• Shutdown Current (All States): 1 µA
• Overtemperature Protection
• Available Packages:
- 8-Lead MSOP
- 8-Lead 2x3 DFN
The
MCP1642B/D
devices
are
compact,
high-efficiency, fixed-frequency, synchronous step-up
DC-DC converters. This family of devices provides an
easy-to-use power supply solution for applications
powered by either one-cell, two-cell, or three-cell
alkaline, Ultimate Lithium, NiCd, NiMH, one-cell Li-Ion
or Li-Polymer batteries.
Low-voltage technology allows the regulator to start-up
without high inrush current or output voltage overshoot
from a low voltage input. High efficiency is
accomplished by integrating the low-resistance
N-Channel Boost switch and synchronous P-Channel
switch. All compensation and protection circuitry are
integrated to minimize the number of external
components. An open-drain Power Good output is
provided to indicate when the output voltage is within
10% of regulation and facilitates the interface with an
MCU. For standby applications, MCP1642B provides a
“true output disconnect” from input to output while in
shutdown (EN = GND). An additional device option
(MCP1642D) is available and connects “input to output
bypass” while in shutdown. Both options consume less
than 1 µA of input current.
For the adjustable (ADJ) device options, the output
voltage is set by a small external resistor divider. Fixed
VOUT device options do not require external divider
resistors. Two package options, 8-lead MSOP and 8lead 2x3 DFN, are available.
Applications
• One, Two and Three-Cell Alkaline, Lithium
Ultimate and NiMH/NiCd Portable Products
• Single-Cell Li-Ion to 5V Converters
• PIC® MCU Power
• USB Emergency Backup Charger from Batteries
• Personal Medical Products
• Wireless Sensors
• Hand-Held Instruments
• GPS Receivers
• +3.3V to +5.0V Distributed Power Supply
Package Types
MCP1642B/D-xx
MSOP
MCP1642B/D-xx
2x3 DFN*
EN 1
8 VIN
NC 2
7 SGND
NC 2
PG 3
6 PGND
PG 3
VOUT 4
VOUT 4
5 SW
MCP1642B/D-ADJ
MSOP
EN 1
8 VIN
VFB 2
7 SGND
VFB 2
PG 3
6 PGND
PG 3
VOUT 4
5 SW
EP
9
7 SGND
6 PGND
5 SW
MCP1642B/D-ADJ
2x3 DFN*
EN 1
VOUT 4
8 VIN
8 VIN
EN 1
EP
9
7 SGND
6 PGND
5 SW
* Includes Exposed Thermal Pad (EP); see Table 3-1.
2014 Microchip Technology Inc.
DS20005253A-page 1
MCP1642B/D
Typical Application
L1
4.7 µH
VOUT
3.3V
CIN
4.7...10 µF
VIN= 0.9 to 1.6V
VIN
+
SW
VOUT
COUT
4.7...10 µF
ALKALINE
MCP1642B-33
NC
PG
EN
-
GND
ON
OFF
L
4.7 µH
VOUT
CIN
4.7...10 µF
5.0V
SW
VOUT
VIN
VIN= 1.8 to 3.2V
MCP1642D-ADJ
VFB
ALKALINE
+
RTOP
976 k
RBOT
309 k
EN
-
COUT
4.7...10 µF
RPG
1 M
ON
ALKALINE
+
OFF
®
From PIC MCU I/O
GND
PG
To PIC MCU I/O
-
100
90
VIN = 1.2V, VOUT = 3.3V
Efficiency (%)
80
70
VIN = 2.5V, VOUT = 5.0V
60
50
40
30
20
10
0
1
10
100
1000
IOUT (mA)
DS20005253A-page 2
2014 Microchip Technology Inc.
MCP1642B/D
1.0
ELECTRICAL
CHARACTERISTICS
† Notice: Stresses above those listed under “Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of
the device at those or any other conditions above those
indicated in the operational sections of this
specification is not intended. Exposure to maximum
rating conditions for extended periods may affect
device reliability.
Absolute Maximum Ratings †
EN, FB, VIN, VSW, VOUT – GND .......................... +6.5V
EN, FB ...... (GND – 0.3V)
Output Short-Circuit Current ...................... Continuous
Output Current Bypass Mode........................... 800 mA
Power Dissipation ............................ Internally Limited
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
DC CHARACTERISTICS
Electrical Characteristics: Unless otherwise indicated, VIN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V,
IOUT = 15 mA, TA = +25°C, MCP1642B/D-ADJ. Boldface specifications apply over the TA range of -40°C to +85°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Conditions
Minimum Start-Up Voltage
VIN
—
0.65
0.8
V
Note 1
—
0.9
1.8
V
MCP1642B/D-50, Note 1
Minimum Input Voltage
After Start-Up
VIN
—
0.35
—
V
Note 1, Note 5
—
0.5
—
V
Note 1, Note 5, MCP1642B/D-50
Output Voltage Adjust.
Range
(MCP1642B/D-ADJ)
VOUT
1.8
—
5.5
V
VOUT VIN (MCP1642B/D-ADJ);
Note 2
Output Voltage
(MCP1642B/D-XX)
VOUT
—
1.8
—
V
VIN < 1.8V, MCP1642B/D-18,
Note 2
—
3.0
—
V
VIN < 3.0V, MCP1642B/D-30,
Note 2
—
3.3
—
V
VIN < 3.3V, MCP1642B/D-33,
Note 2
—
5.0
—
V
VIN < 5.0V, MCP1642B/D-50,
Note 2
—
175
—
mA
1.2V VIN, 1.8V VOUT, Note 5
—
300
—
mA
1.5V VIN, 3.3V VOUT, Note 5
—
800
—
mA
3.3V VIN, 5.0V VOUT, Note 5
Input Characteristics
Maximum Output Current
IOUT
Feedback Voltage
VFB
1.173
1.21
1.247
V
Feedback Input
Bias Current
IVFB
—
1.0
—
nA
Note 1:
2:
3:
4:
5:
Note 5
Resistive load, 1 mA.
For VIN > VOUT, VOUT will not remain in regulation.
IQPWM is measured from VOUT; VOUT is externally supplied with a voltage higher than the nominal 3.3V
output (device is not switching), no load. VIN quiescent current will vary with boost ratio. VIN quiescent
current can be estimated by: (IQPWM * (VOUT/VIN)).
220 resistive load, 3.3V VOUT (15 mA).
Determined by characterization, not production tested.
2014 Microchip Technology Inc.
DS20005253A-page 3
MCP1642B/D
DC CHARACTERISTICS (CONTINUED)
Electrical Characteristics: Unless otherwise indicated, VIN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V,
IOUT = 15 mA, TA = +25°C, MCP1642B/D-ADJ. Boldface specifications apply over the TA range of -40°C to +85°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Quiescent Current –
PWM Mode
IQPWM
—
400
500
µA
Measured at VOUT, EN = VIN,
IOUT = 0 mA, Note 3
Quiescent Current –
Shutdown
IQSHDN
—
1
—
µA
VOUT = EN = GND, IOUT = 0 mA
includes N-Channel and
P-Channel Switch Leakage
NMOS Switch Leakage
INLK
—
0.5
—
µA
VIN = VSW = 5V,
VOUT = 5.5V,
VEN = VFB = GND
PMOS Switch Leakage
IPLK
—
0.2
—
µA
VIN = VSW = GND,
VOUT = 5.5V
NMOS Switch
ON Resistance
RDS(ON)N
—
0.15
—
VIN = 3.3V, ISW = 250 mA, Note 5
PMOS Switch
ON Resistance
RDS(ON)P
—
0.3
—
VIN = 3.3V, ISW = 250 mA, Note 5
IN(MAX)
—
1.8
—
A
Note 5
NMOS Peak
Switch Current Limit
Accuracy
Line Regulation
Load Regulation
Note 1:
2:
3:
4:
5:
Conditions
VFB%
-3
—
3
%
MCP1642B/D-ADJ, VIN = 1.2V
VOUT%
-3
—
3
%
MCP1642B/D-18, VIN = 1.2V
-3
—
3
%
MCP1642B/D-30, VIN = 1.2V
-3
—
3
%
MCP1642B/D-33, VIN = 1.2V
-3
—
3
%
VFB/VFB)
/VIN|
-0.5
0.01
0.5
%/V
MCP1642B/D-ADJ,
VIN = 1.5V to 3.0V, IOUT = 25 mA
MCP1642B/D-50, VIN = 2.5V
VOUT/VOUT)
/VIN|
-0.5
0.05
0.5
%/V
MCP1642B/D-18,
VIN = 1.0V to 1.5V, IOUT = 25 mA
-0.5
0.01
0.5
%/V
MCP1642B/D-30,
VIN = 1.5V to 2.5V, IOUT = 25 mA
-0.5
0.01
0.5
%/V
MCP1642B/D-33,
VIN = 1.5V to 3.0V, IOUT = 25 mA
-0.5
0.01
0.5
%/V
MCP1642B/D-50,
VIN = 2.5V to 4.2V, IOUT = 25 mA
VFB/VFB|
-1.5
0.05
1.5
%
IOUT = 25 mA to 150 mA,
VIN = 1.5V
VOUT/VOUT|
-1.5
0.1
1.5
%
MCP1642B/D-18, VIN = 1.5V,
IOUT = 25 mA to 75 mA
-1.5
0.1
1.5
%
MCP1642B/D-30, VIN = 1.5V,
IOUT = 25 mA to 125 mA
-1.5
0.1
1.5
%
MCP1642B/D-33, VIN = 1.5V,
IOUT = 25 mA to 150 mA
—
0.5
—
%
MCP1642B/D-50, VIN = 3.0V,
IOUT = 25 mA to 500 mA, Note 5
Resistive load, 1 mA.
For VIN > VOUT, VOUT will not remain in regulation.
IQPWM is measured from VOUT; VOUT is externally supplied with a voltage higher than the nominal 3.3V
output (device is not switching), no load. VIN quiescent current will vary with boost ratio. VIN quiescent
current can be estimated by: (IQPWM * (VOUT/VIN)).
220 resistive load, 3.3V VOUT (15 mA).
Determined by characterization, not production tested.
DS20005253A-page 4
2014 Microchip Technology Inc.
MCP1642B/D
DC CHARACTERISTICS (CONTINUED)
Electrical Characteristics: Unless otherwise indicated, VIN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V,
IOUT = 15 mA, TA = +25°C, MCP1642B/D-ADJ. Boldface specifications apply over the TA range of -40°C to +85°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Maximum Duty Cycle
DCMAX
—
90
—
%
Switching Frequency
fSW
0.85
1.0
1.15
MHz
EN Input Logic High
VIH
75
—
—
% of VIN IOUT = 1 mA,
for MCP1642B/D-50 VIN = 2.5V
EN Input Logic Low
VIL
—
—
20
% of VIN IOUT = 1 mA,
for MCP1642B/D-50 VIN = 2.5V
EN Input Leakage Current
Conditions
Note 5
Note 5, IOUT = 65 mA,
for MCP1642B/D-50 VIN = 2.5V
IENLK
—
0.1
—
µA
VEN = 1.2V
Power Good Threshold
PGTHF
—
90
—
%
VFB Falling, Note 5
Power Good Hysteresis
PGHYS
—
3
—
%
Note 5
Power Good Output Low
PGLOW
—
0.4
—
V
ISINK = 5 mA, VFB = 0V, Note 5
PGDELAY
—
600
—
µs
Note 5
Power Good Output
Response
Power Good Output Delay
PGRES
—
250
—
µs
Note 5
Power Good Input Voltage
Operating Range
VPG_VIN
0.9
—
5.5
V
ISINK = 5 mA, VFB = 0V, Note 5
Power Good
Leakage Current
PGLEAK
—
0.01
—
µA
VPG = 5.5V,
VOUT in Regulation, Note 5
Soft Start Time
tSS
—
550
—
µs
Thermal Shutdown
Die Temperature
TSD
—
150
—
C
EN Low to High,
90% of VOUT, Note 4, Note 5
Note 5
TSDHYS
—
35
—
C
Note 5
Die Temperature
Hysteresis
Note 1:
2:
3:
4:
5:
Resistive load, 1 mA.
For VIN > VOUT, VOUT will not remain in regulation.
IQPWM is measured from VOUT; VOUT is externally supplied with a voltage higher than the nominal 3.3V
output (device is not switching), no load. VIN quiescent current will vary with boost ratio. VIN quiescent
current can be estimated by: (IQPWM * (VOUT/VIN)).
220 resistive load, 3.3V VOUT (15 mA).
Determined by characterization, not production tested.
TEMPERATURE SPECIFICATIONS
Electrical Characteristics: Unless otherwise indicated, VIN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V,
IOUT = 15 mA, TA = +25°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Operating Ambient Temperature
Range
TA
-40
—
+85
°C
Storage Temperature Range
TA
-65
—
+150
°C
Maximum Junction Temperature
TJ
—
—
+150
°C
Thermal Resistance, 8L-MSOP
JA
—
211
—
°C/W
Thermal Resistance, 8L-2x3 DFN
JA
—
68
—
°C/W
Conditions
Temperature Ranges
Steady State
Transient
Package Thermal Resistances
2014 Microchip Technology Inc.
DS20005253A-page 5
MCP1642B/D
NOTES:
DS20005253A-page 6
2014 Microchip Technology Inc.
MCP1642B/D
2.0
TYPICAL PERFORMANCE CURVES
Note:
The graphs and tables provided following this note are a statistical summary based on a limited number 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.
Note: Unless otherwise indicated, VIN = EN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V, ILOAD = 15 mA,
TA = +25°C (MCP1642B/D-ADJ, MSOP-8 package).
100
500
80
450
Efficiency (%)
IQ PWM Mode (µA)
475
425
VOUT = 5.0V
400
375
VOUT = 3.3V
VIN = 1.6V
70
VIN = 1.2V
60
50
40
30
350
VOUT = 2.0V
20
325
10
300
0
-40
-25
-10
5
20
35
50
65
Ambient Temperature (°C)
FIGURE 2-1:
Temperature.
80
VOUT IQPWM vs. Ambient
0.1
100
IOUT = 50 mA
VIN = 1.8V
90
3.312
Efficiency (%)
3.310
3.308
3.306
10
IOUT (mA)
100
1000
2.0V VOUT Mode Efficiency
VOUT = 3.3V
VIN = 2.5V
80
VIN = 1.2V
1
FIGURE 2-4:
vs. IOUT.
3.314
VOUT (V)
VOUT = 2.0V
90
VIN = 1.2V
VIN = 1.2V
70
60
50
40
30
20
10
3.304
-40
-25
-10
5
20
35
50
65
Ambient Temperature (°C)
3.3V VOUT vs. Ambient
FIGURE 2-2:
Temperature.
0
80
0.1
90
IOUT = 50 mA
5.000
VIN = 2.5V
4.995
4.990
4.985
100
1000
VOUT = 5.0V
80
Efficiency (%)
VOUT (V)
5.005
10
IOUT (mA)
3.3V VOUT Mode Efficiency
FIGURE 2-5:
vs. IOUT.
100
5.010
1
VIN = 3.6V
70
VIN = 2.5V
60
50
40
30
20
VIN = 1.8V
10
4.980
-40
FIGURE 2-3:
Temperature.
-25
-10
5
20 35 50 65
Ambient Temperature (°C)
80
5.0V VOUT vs. Ambient
2014 Microchip Technology Inc.
0
0.1
FIGURE 2-6:
vs. IOUT.
1
10
IOUT (mA)
100
1000
5.0V VOUT Mode Efficiency
DS20005253A-page 7
MCP1642B/D
Note: Unless otherwise indicated, VIN = EN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V, ILOAD = 15 mA,
TA = +25°C (MCP1642B/D-ADJ, MSOP-8 package).
1.50
1400
VOUT = 5.0V
1200
1.30
VOUT = 3.3V
1.10
VIN (V)
IOUT (mA)
1000
VOUT = 5.0V
800
600
VOUT = 2.0V
Start-up
0.70
400
Shutdown
0.50
TA = +25°C
TA = +85°C
200
0.30
0
0.8
1.2
1.6
FIGURE 2-7:
2
2.4 2.8
VIN (V)
3.2
3.6
4
0
4.4
Maximum IOUT vs. VIN.
20
80
100
Switching Frequency (kHz)
1004
IOUT = 15 mA
3.302
TA = 25°C
3.300
3.298
3.296
TA = 85°C
3.294
TA = -40°C
3.292
VOUT = 3.3V
1000
996
992
988
3.290
0.8
1
1.2 1.4 1.6 1.8
2
2.2 2.4 2.6 2.8
-40
3
-25
-10
5
20
35
50
65
Ambient Temperature (°C)
VIN (V)
FIGURE 2-8:
4.5
VOUT = 3.3V
0.65
80
fSW vs. Ambient
FIGURE 2-11:
Temperature.
3.3V VOUT vs. VIN.
0.70
VOUT = 5.0V
4
Start-up
3.5
0.60
0.55
VIN (V)
VIN (V)
40
60
IOUT (mA)
FIGURE 2-10:
5.0V VOUT Minimum
Start-Up and Shutdown VIN into Resistive Load
vs. IOUT.
3.304
VOUT (V)
0.90
0.50
Shutdown
0.45
3
VOUT = 3.3V
2.5
VOUT = 2.0V
2
1.5
0.40
1
0.35
0.5
0.30
0
0
20
40
60
IOUT (mA)
80
100
FIGURE 2-9:
3.3V VOUT Minimum
Start-Up and Shutdown VIN into Resistive Load
vs. IOUT.
DS20005253A-page 8
0
5
10
15
IOUT (mA)
20
25
FIGURE 2-12:
PWM Pulse-Skipping Mode
Threshold vs. IOUT.
2014 Microchip Technology Inc.
MCP1642B/D
Note: Unless otherwise indicated, VIN = EN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V, ILOAD = 15 mA,
TA = +25°C (MCP1642B/D-ADJ, MSOP-8 package).
IIN (mA)
100
VOUT
20 mV/div
AC coupled
IOUT = 100 mA
10
VOUT = 5.0V
VOUT = 3.3V
1
VSW
2V/div
VOUT = 2.0V
0.1
0.8
1.2
1.6
2
FIGURE 2-13:
Current vs. VIN.
2.4 2.8
VIN (V)
3.2
3.6
4
4.4
1 µs/div
Average of No Load Input
2.5
Switch Resistance (:)
IL
200 mA/div
FIGURE 2-16:
MCP1642B/D High Load
PWM Mode Waveforms.
0.25
2
IOUT = 15 mA
0.2
N - Channel
1.5
0.15
1
0.1
VOUT
1V/div
P - Channel
0.5
VIN
1V/div
0.05
0
0
1
1.4
1.8
2.2 2.6
3
3.4
> VIN or VOUT
3.8
VEN
1V/div
4.2
FIGURE 2-14:
N-Channel and P-Channel
RDSON vs. > of VIN or VOUT.
200 µs/div
FIGURE 2-17:
3.3V Start-Up After Enable.
IOUT = 1 mA
VOUT
20 mV/div
AC coupled
I OUT = 15 mA
VOUT
2V/div
VSW
1V/div
IL
100 mA/div
VIN
1V/div
IL
200 mA/div
200 µs/div
1 µs/div
FIGURE 2-15:
MCP1642B/D 3.3V VOUT
Light Load PWM Mode Waveforms.
2014 Microchip Technology Inc.
FIGURE 2-18:
VIN = VENABLE.
3.3V Start-Up When
DS20005253A-page 9
MCP1642B/D
Note: Unless otherwise indicated, VIN = EN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V, ILOAD = 15 mA,
TA = +25°C (MCP1642B/D-ADJ, MSOP-8 package).
VOUT
100 mV/div
AC coupled
IOUT
100 mA/div
Step from 20 mA to 150 mA
400 µs/div
FIGURE 2-19:
MCP1642B 3.3V VOUT Load
Transient Waveforms.
VOUT
100 mV/div
AC coupled
VIN
1V/div
Step from 1.2V to 2.4V
400 µs/div
FIGURE 2-20:
Waveforms.
DS20005253A-page 10
3.3V VOUT Line Transient
2014 Microchip Technology Inc.
MCP1642B/D
3.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
PIN FUNCTION TABLE
MCP1642B/D-XX MCP1642B/D-ADJ
MSOP, 2x3 DFN
MSOP, 2x3 DFN
3.1
1
1
Symbol
Description
EN
Enable pin. Logic high enables operation. Do not allow this pin
to float.
2
—
NC
Not Connected.
—
2
VFB
Reference Voltage pin. Connect VFB to an external resistor
divider to set the output voltage (for fixed VOUT options, this pin
is not connected).
3
3
PG
Open-Drain Power Good pin. Indicates when the output voltage
is within regulation.
4
4
VOUT
5
5
SW
6
6
PGND
Power Ground reference.
7
7
SGND
Signal Ground reference.
8
8
VIN
Input supply voltage. Local bypass capacitor required.
9
9
EP
Exposed Thermal Pad (2x3 DFN only).
Boost Converter Output.
Boost and Rectifier Switch input. Connect boost inductor
between SW and VIN.
Enable Pin (EN)
The EN pin is a logic-level input used to enable or
disable device switching and lower quiescent current
while disabled. A logic high (>75% of VIN) will enable
the regulator output. A logic low ( VOUT SITUATION
To calculate the resistor divider values for the
MCP1642B/D, the following equation can be used.
Where RTOP is connected to VOUT, RBOT is connected
to GND and both are connected to the VFB input pin:
For VIN > VOUT, the output voltage will not remain in
regulation. VIN > VOUT is an unusual situation for a
boost converter, and there is a common issue when
two alkaline cells (2 x 1.6V typical) are used to boost to
3.0V output. A minimum headroom of approximately
200 to 300 mV between VOUT and VIN must be
ensured, unless a low frequency higher than the PWM
output ripple on VOUT is expected. This ripple and its
frequency are VIN dependent.
EQUATION 5-1:
5.3
5.2
Adjustable Output Voltage
Calculations
R TOP
V OUT
= R BOT ------------- – 1
V FB
EXAMPLE 1:
VOUT = 3.3V
VFB
= 1.21V
RBOT = 309 k
RTOP = 533.7 k (standard value = 536 k)
EXAMPLE 2:
VOUT = 5.0V
VFB
= 1.21V
RBOT = 309 k
RTOP = 967.9 k (standard value = 976 k)
There are some potential issues with higher-value
resistors. For small surface-mount resistors,
environment contamination can create leakage paths
that significantly change the resistive divider ratio,
which in turn affects the output voltage. The FB input
leakage current can also impact the divider and change
the output voltage tolerance.
For boost converters, the removal of the feedback
resistors during operation must be avoided. In this
case, the output voltage will increase above the absolute maximum output limits of the MCP1642B/D and
damage the device (for additional information, see
Application Note AN1337).
2014 Microchip Technology Inc.
Power Good Output
The Power Good output is meant to provide a method
that gives information about the output state of the
device. The Power Good comparator is triggered when
VOUT reaches approximately 90% of regulation (on the
falling edge).
The PG pin is an open-drain output, which should be
connected to VOUT through an external pull-up resistor.
It is recommended to use a high-value resistor (to sink
µA from output) in order to use less power while
interfacing with an I/O PIC MCU port.
The Power Good block is internally supplied by the
maximum between the input and output voltage, and
the minimum voltage necessary is 0.9V. This is
important for applications in which the Power Good pin
is pulled-up to an external supply. If the output voltage
is less than 0.9V (e.g., due to an overcurrent situation
or an output short circuit, and also if the device is in
Shutdown - EN = GND), the input voltage has to be
high enough to drive the Power Good circuitry.
Power Good delay time is measured between the time
when VOUT starts to regulate and the time when there
is a response from Power Good output. Power Good
response time is measured between the time when
VOUT goes out of regulation with a 10% drop, and the
time when Power Good output gets to a low level. Both
Power Good delay time and Power Good response
time are specified in the DC Characteristics table.
Additionally, there are no blanking time or delays; there
is only a 3% hysteresis of the Power Good comparator.
Due to the dynamic response, MCU must interpret
longer transients.
DS20005253A-page 17
MCP1642B/D
When VOUT resumes to a value higher than 93%, the
PG pin switches to high level.
600 µs (typ.)
250 µs (typ.)
VOUT
PG DELAY
PG RESPONSE
PG
Where:
dV
=
Ripple voltage
dt
=
ON time of the N-Channel switch
(DC x 1/FSW)
Table 5-1 contains the recommended range for the
input and output capacitor value.
Power Good Timing Diagram.
Input Capacitor Selection
The boost input current is smoothed by the boost
inductor, reducing the amount of filtering necessary at
the input. Some capacitance is recommended to
provide decoupling from the source. Low ESR X5R or
X7R are well suited, since they have a low temperature
coefficient and small size. For light-load applications,
4.7 µF of capacitance is sufficient at the input. For
high-power applications that have high source
impedance or long leads which connect the battery to
the input, 10 µF of capacitance is recommended.
Additional input capacitance can be added to provide a
stable input voltage.
Table 5-1 contains the recommended range for the
input capacitor value.
5.5
dV
IOUT = C OUT -------
dt
TABLE 5-1:
FIGURE 5-1:
5.4
EQUATION 5-2:
Output Capacitor Selection
The output capacitor helps provide a stable output
voltage during sudden load transients and reduces the
output voltage ripple. As with the input capacitor, X5R
and X7R ceramic capacitors are well suited for this
application. Using other capacitor types (aluminum or
tantalum) with large ESR has impact on the converter's
efficiency (see AN1337) and maximum output power.
The MCP1642B/D devices are internally compensated,
so output capacitance range is limited. See Table 5-1
for the recommended output capacitor range.
An output capacitance higher than 10 µF adds a better
load step response and high-frequency noise
attenuation, especially while stepping from light current
loads to heavy current loads. In addition, 2 x 10 µF
output capacitors ensure a better recovery of the output
after a short period of overloading.
While the N-Channel switch is on, the output current is
supplied by the output capacitor COUT. The amount of
output capacitance and equivalent series resistance
will have a significant effect on the output ripple
voltage. While COUT provides load current, a voltage
drop also appears across its internal ESR that results
in ripple voltage.
DS20005253A-page 18
CAPACITOR VALUE RANGE
CIN
COUT
Minimum
4.7 µF
10 µF
Maximum
—
100 µF
5.6
Inductor Selection
The MCP1642B/D devices are designed to be used
with small surface-mount inductors; the inductance
value can range from 2.2 µH to 6.8 µH. An inductance
value of 4.7 µH is recommended to achieve a good
balance between the inductor size, the converter load
transient response and the minimized noise.
TABLE 5-2:
MCP1642B/D
RECOMMENDED INDUCTORS
Part Number
Value
DCR
(µH) (typ.)
ISAT
(A)
Size
WxLxH (mm)
Coilcraft
LPS4018-472
4.7
0.125
1.9
4.1x4.1x1.8
XFL4020-472
4.7
0.057
2.7
4.2x4.2x2.1
LPS5030-472
4.7
0.083
2
5x5x3
LPS6225-472
4.7
0.065
3.2
6.2x6.2x2.5
MSS6132-472
4.7
0.043
2.84
6.1x6.1x3.2
Würth Elektronik
744025004 Type WE-TPC
4.7
0.1
1.7
2.8x2.8x2.8
744042004 WE-TPC
4.7
0.07
1.65
4.8x4.8x1.8
744052005 WE-TPC
5
0.047
1.8
5.8x5.8x1.8
7447785004 WE-PD
4.7
0.06
2.5
6.2x5.9x3.3
B82462A2472M000
4.7
0.084
2.00
6.0x6.0x2.5
B82462G4472M
4.7
0.04
1.8
6.3x6.3x3.0
TDK/EPCOS
Several parameters are used to select the correct
inductor: maximum rated current, saturation current
and copper resistance (ESR). For boost converters, the
inductor current can be much higher than the output
current. The lower the inductor ESR, the higher the
efficiency of the converter: a common trade-off in size
versus efficiency.
The saturation current typically specifies a point at
which the inductance has rolled off a percentage of the
rated value. This can range from a 20% to 40%
reduction in inductance. As inductance rolls off, the
inductor ripple current increases, as does the peak
switch current. It is important to keep the inductance
from rolling off too much, causing switch current to
reach the peak limit.
2014 Microchip Technology Inc.
MCP1642B/D
5.7
Thermal Calculations
The MCP1642B/D devices are available in two different
packages (MSOP-8 and 2 x 3 DFN-8). By calculating
the power dissipation and applying the package
thermal resistance (JA), the junction temperature is
estimated. The maximum continuous junction
temperature rating for the MCP1642B/D family of
devices is +125°C.
To quickly estimate the internal power dissipation for
the switching boost regulator, an empirical calculation
using measured efficiency can be used. Given the
measured efficiency, the internal power dissipation is
estimated by Equation 5-3.
EQUATION 5-3:
V OUT I OUT
------------------------------- – VOUT I OUT = P Dis
Efficiency
The difference between the first term, input power, and
the second term, power delivered, is the power dissipation of the MCP1642B/D devices. This is an estimate
assuming that most of the power lost is internal to the
MCP1642B/D and not CIN, COUT and the inductor.
There is some percentage of power lost in the boost
inductor, with very little loss in the input and output
capacitors. For a more accurate estimation of internal
power dissipation, subtract the IINRMS2 x LESR power
dissipation.
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
switching high-current paths, short and wide traces
should be used. Therefore, it is important that the input
and output capacitors be placed as close as possible to
the MCP1642B/D to minimize the loop area.
The feedback resistors and feedback signal should be
routed away from the switching node and the switching
current loop. When possible, ground planes and traces
should be used to help shield the feedback signal and
minimize noise and magnetic interference.
+VIN
L
CIN
GND
MCP1642
COUT
1
RTOP
RBOT
+VOUT
Via To Bottom
Plane
Enable
FIGURE 5-2:
Power Good
MCP1642B/D Recommended Layout, Applicable to Both Packages.
2014 Microchip Technology Inc.
DS20005253A-page 19
MCP1642B/D
6.0
TYPICAL APPLICATION CIRCUITS
L
4.7 µH
VOUT
VIN
5.0V @ min. 500 mA
SW
3.3V to 4.2V
VOUT
VIN
LI-ION
+
MCP1642B-ADJ
CIN
10 µF
EN
FIGURE 6-1:
VFB
PGND
CC
27 pF
COUT
10 µF
RBOT
309 k
PG
-
RTOP
976 k
SGND
Portable USB Powered by Li-Ion.
L
4.7 µH
VIN
1.8V to 3.6V
SW
VOUT
5.0V @ min. 500 mA
VOUT
VIN
+
CIN
10 µF
COUT
10 µF
MCP1642B-50
EN
PG
NC
PGND SGND
+
28.7
Service Estimate (hours)
30.0
-
® AA
Energizer®
MAX®
AA
Energizer® MAX
Energizer®
UltimateLithium
LithiumAA
AA
Energizer® Ultimate
25.0
20.0
15.0
12.7
10.0
5.8
5.0
1.8
0.3
0.0
50 mA
250 mA
2.3
500 mA
Constant Output Current with 5V DC VOUT
Note:
Service estimates apply to using two Energizer® MAX® AA or Energizer® Ultimate Lithium AA
batteries as the power source. Note that, if PG or feedback divider network is used, some
additional input drain current should be included, but there will be negligible effects on the service
estimates at these three load currents.
FIGURE 6-2:
Portable USB Powered by Two Energizer® MAX® AA or Energizer® Ultimate Lithium
AA Batteries with the 5.0V Fixed Option of the MCP1642B.
DS20005253A-page 20
2014 Microchip Technology Inc.
MCP1642B/D
7.0
PACKAGING INFORMATION
7.1
Package Marking Information
8-Lead DFN (2x3x0.9 mm)
Example
Part Number
Code
MCP1642B-18I/MC
AJY
MCP1642BT-18I/MC
AJY
MCP1642B-30I/MC
AJU
MCP1642BT-30I/MC
AJU
MCP1642B-33I/MC
AJQ
MCP1642BT-33I/MC
AJQ
MCP1642B-50I/MC
AJL
MCP1642BT-50I/MC
AJL
MCP1642B-ADJI/MC
AKC
MCP1642BT-ADJI/MC
AKC
MCP1642D-18I/MC
AKA
MCP1642DT-18I/MC
AKA
MCP1642D-30I/MC
AJW
MCP1642DT-30I/MC
AJW
MCP1642D-33I/MC
AJS
MCP1642DT-33I/MC
AJS
MCP1642D-50I/MC
AJN
MCP1642DT-50I/MC
AJN
MCP1642D-ADJI/MC
AKE
MCP1642DT-ADJI/MC
AKE
8-Lead MSOP (3x3 mm)
AJY
348
25
Example
42B50I
348256
Legend: XX...X
Y
YY
WW
NNN
e3
*
Note:
Customer-specific information
Year code (last digit of calendar year)
Year code (last 2 digits of calendar year)
Week code (week of January 1 is week ‘01’)
Alphanumeric traceability code
Pb-free JEDEC® designator for Matte Tin (Sn)
This package is Pb-free. The Pb-free JEDEC designator ( e3 )
can be found on the outer packaging for this package.
In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line, thus limiting the number of available
characters for customer-specific information.
2014 Microchip Technology Inc.
DS20005253A-page 21
MCP1642B/D
!""#$%&
'
)RUWKHPRVWFXUUHQWSDFNDJHGUDZLQJVSOHDVHVHHWKH0LFURFKLS3DFNDJLQJ6SHFLILFDWLRQORFDWHGDW
KWWS ZZZPLFURFKLSFRPSDFNDJLQJ
e
D
b
N
N
L
K
E2
E
EXPOSED PAD
NOTE 1
NOTE 1
2
1
1
2
D2
BOTTOM VIEW
TOP VIEW
A
A3
A1
NOTE 2
8QLWV
'LPHQVLRQ/LPLWV
1XPEHURI3LQV
0,//,0(7(56
0,1
1
120
0$;
3LWFK
H
2YHUDOO+HLJKW
$
6WDQGRII
$
&RQWDFW7KLFNQHVV
$
5()
2YHUDOO/HQJWK
'
%6&
2YHUDOO:LGWK
(
([SRVHG3DG/HQJWK
'
±
([SRVHG3DG:LGWK
(
±
E
&RQWDFW/HQJWK
/
&RQWDFWWR([SRVHG3DG
.
±
±
&RQWDFW:LGWK
%6&
%6&
'
3LQYLVXDOLQGH[IHDWXUHPD\YDU\EXWPXVWEHORFDWHGZLWKLQWKHKDWFKHGDUHD
3DFNDJHPD\KDYHRQHRUPRUHH[SRVHGWLHEDUVDWHQGV
3DFNDJHLVVDZVLQJXODWHG
'LPHQVLRQLQJDQGWROHUDQFLQJSHU$60(
工商网监
湘ICP备2023018690号
