MCP1623/24
Low-Voltage Input Boost Regulator
for PIC® Microcontrollers
Features
General Description
• Up to 96% Typical Efficiency
• 425 mA Typical Peak Input Current Limit:
- IOUT > 50 mA @ 1.2V VIN, 3.3V VOUT
- IOUT > 175 mA @ 2.4V VIN, 3.3V VOUT
- IOUT > 175 mA @ 3.3V VIN, 5.0V VOUT
• Low Start-Up Voltage: 0.65V, 3.3V VOUT @ 1 mA
(typical)
• Low Operating Input Voltage: 0.35V, typical
3.3VOUT @ 1 mA
• Adjustable Output Voltage Range: 2.0V to 5.5V
• Maximum Input Voltage VOUT < 5.5V
• Automatic PFM/PWM Operation (MCP1624)
• PWM-Only Operation (MCP1623)
• PWM Operation: 500 kHz
• Low Device Quiescent Current: 19 µA, typical
PFM Mode
• Internal Synchronous Rectifier
• Internal Compensation
• Inrush Current Limiting and Internal Soft Start
• True Load Disconnect
• Shutdown Current (All States): VOUT, VOUT will not remain in regulation.
IQ is measured from VOUT; VIN quiescent current will vary with boost ratio. VIN quiescent current can be
estimated by: (IQPFM * (VOUT/VIN)), (IQPWM * (VOUT/VIN)).
Peak current limit determined by characterization, not production tested
220 resistive load, 3.3VOUT (15 mA).
2010-2016 Microchip Technology Inc.
DS40001420D-page 3
MCP1623/24
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.
Boldface specifications apply over the TA range of -40°C to +85°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Conditions
RDS(ON)P
—
0.9
—
IN(MAX)
300
425
—
mA
Note 4
VOUT%
-7.4
—
+7.4
%
Includes line and load
regulation; VIN = 1.5V,
IOUT = 50 mA
Line Regulation
VOUT/
VOUT)/
VIN|
—
0.01
—
%/V
Load Regulation
VOUT/
VOUT|
—
0.01
—
%
Maximum Duty Cycle
DCMAX
—
90
—
%
Switching Frequency
fSW
370
500
630
kHz
EN Input Logic High
VIH
90
—
—
%of VIN IOUT = 1 mA
EN Input Logic Low
VIL
—
—
20
%of VIN IOUT = 1 mA
µA
VEN = 5V
PMOS Switch ON Resistance
NMOS Peak Switch Current
Limit
VOUT Accuracy
EN Input Leakage Current
IENLK
—
0.005
—
Soft Start Time
tSS
—
750
—
µS
Thermal Shutdown Die
Temperature
TSD
—
150
—
C
TSDHYS
—
10
—
C
Die Temperature Hysteresis
Note 1:
2:
3:
4:
5:
VIN = 3.3V, ISW = 100 mA
VIN = 1.5V to 3V
IOUT = 25 mA
IOUT = 25 mA to 50 mA;
VIN = 1.5V
EN Low-to-High, 90% of
VOUT (Note 5)
3.3 k resistive load, 3.3VOUT (1 mA).
For VIN > VOUT, VOUT will not remain in regulation.
IQ is measured from VOUT; VIN quiescent current will vary with boost ratio. VIN quiescent current can be
estimated by: (IQPFM * (VOUT/VIN)), (IQPWM * (VOUT/VIN)).
Peak current limit determined by characterization, not production tested
220 resistive load, 3.3VOUT (15 mA).
TEMPERATURE SPECIFICATIONS
Electrical Specifications: Unless otherwise indicated, VIN = 1.2V, COUT = CIN = 10 µF, L = 4.7 µH, VOUT = 3.3V,
IOUT = 15 mA, TA = +25°C.
Boldface specifications apply over the TA range of -40°C to +85°C.
Parameters
Sym.
Min.
Typ.
Max.
Units
Operating Junction Temperature
Range
TJ
-40
—
+125
°C
Storage Temperature Range
TA
-65
—
+150
°C
TJ
—
—
+150
°C
Thermal Resistance, 6LD-SOT-23
JA
—
190.5
—
°C/W
Thermal Resistance, 8LD-2x3 DFN
JA
—
75
—
°C/W
Conditions
Temperature Ranges
Maximum Junction Temperature
Steady state
Transient
Package Thermal Resistance
DS40001420D-page 4
2010-2016 Microchip Technology Inc.
MCP1623/24
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.
27.5
VOUT = 5.0V
Efficiency (%)
IQ PFM Mode (µA)
25.0
22.5
20.0
17.5
VOUT = 3.3V
15.0
VOUT = 2.0V
12.5
10.0
-40
-25
-10
5
20
35
50
65
80
100
90
VIN = 1.6V
80
70
60
50
40
30
20
10
0.01
0.1
VIN = 1.2V
VIN = 0.8V
1
Ambient Temperature (°C)
FIGURE 2-1:
MCP1624 VOUT IQ vs.
Ambient Temperature in PFM Mode, VIN = 1.2V.
100
90
VIN = 2.5
80
70
60
50
40
30
20
10
0.01
0.1
VOUT = 5.0V
275
250
225
VOUT = 3.3V
200
175
150
-40
-25
-10
5
20
35
50
65
80
VIN = 1.2
1
10
IOUT (mA)
100
1000
FIGURE 2-5:
MCP1624 Efficiency vs.
IOUT, VOUT = 3.3V.
600
100
500
90
VOUT = 3.3V
400
300
VIN = 3.6
80
Efficiency (%)
IOUT (mA)
1000
VIN = 0.8
Ambient Temperature (°C)
FIGURE 2-2:
MCP1623 VOUT IQ vs.
Ambient Temperature in PWM Mode, VIN = 1.2V.
100
FIGURE 2-4:
MCP1624 Efficiency vs.
IOUT, VOUT = 2.0V.
Efficiency (%)
IQ PWM Mode (µA)
300
10
IOUT (mA)
VOUT = 2.0V
VOUT = 5.0V
200
100
70
VIN = 1.8
60
VIN = 1.2
50
40
30
20
0
0
0.5
1
1.5
2
2.5
3
3.5
4
VIN (V)
FIGURE 2-3:
IOUTMAX vs. VOUT.
2010-2016 Microchip Technology Inc.
4.5
5
10
0.01
0.1
1
10
100
1000
IOUT (mA)
FIGURE 2-6:
MCP1624 Efficiency vs.
IOUT, VOUT = 5.0V.
DS40001420D-page 5
MCP1623/24
100
90
80
70
60
50
40
30
20
10
0.01
1.00
VIN =1.6
0.85
VIN (V)
Efficiency (%)
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.
VIN = 1.2
VIN = 0.8
1
10
IOUT (mA)
100
0
1000
20
40
60
IOUT (mA)
80
100
FIGURE 2-10:
Minimum Start-Up and
Shutdown VIN into Resistive Load vs. IOUT,
VOUT = 3.3V.
Switching Frequency (kHz)
525
Efficiency (%)
VIN = 2.5
VIN = 1.2
VIN = 0.8
0.1
1
10
IOUT (mA)
100
VIN (V)
50
VIN = 1.2
30
20
0.1
1
10
IOUT (mA)
100
1000
FIGURE 2-9:
MCP1623 Efficiency vs.
IOUT, VOUT = 5.0V.
DS40001420D-page 6
505
500
495
490
485
480
-25
-10
5
20
35
50
65
80
FIGURE 2-11:
FOSC vs. Ambient
Temperature, VOUT = 3.3V.
VIN = 1.8
60
40
510
Ambient Temperature (°C)
VIN = 3.6
70
515
-40
90
80
520
1000
100
Efficiency (%)
Shutdown
0.25
0.1
FIGURE 2-8:
MCP1623 Efficiency vs.
IOUT, VOUT = 3.3V.
10
0.01
0.55
0.40
FIGURE 2-7:
MCP1623 Efficiency vs.
IOUT, VOUT = 2.0V.
100
90
80
70
60
50
40
30
20
10
0.01
Startup
0.70
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
VOUT = 5.0V
VOUT = 3.3V
VOUT = 2.0V
0
1
2
3
4
5
6
IOUT (mA)
7
8
9
10
FIGURE 2-12:
MCP1623 PWM Pulse
Skipping Mode Threshold vs. IOUT.
2010-2016 Microchip Technology Inc.
MCP1623/24
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.
10000
PWM/PFM
PWM ONLY
1000
IIN (µA)
VOUT = 5.0V
VOUT = 3.3V
VOUT = 2.0V
100
VOUT = 2.0V
VOUT = 3.3V
VOUT = 5.0V
10
0.8
1.1
1.4
1.7
2
2.3
2.6
2.9
3.2
3.5
VIN (V)
Switch Resistance (Ohms)
FIGURE 2-13:
VIN.
Input No Load Current vs.
FIGURE 2-16:
MCP1624 3.3V VOUT PFM
Mode Waveforms.
5
4
P-Channel
3
2
1
N-Channel
0
1
1.5
2
2.5
3
3.5
> VIN or VOUT
4
4.5
5
FIGURE 2-14:
N-Channel and P-Channel
RDSON vs. > of VIN or VOUT.
FIGURE 2-17:
MCP1623 3.3V VOUT
PWM Mode Waveforms.
16
14
IOUT (mA)
12
VOUT = 5.0V
VOUT = 3.3V
VOUT = 2.0V
10
8
6
4
2
0
0
0.5
1
1.5
2
2.5
3
3.5
4
VIN (V)
FIGURE 2-15:
MCP1624 PFM/PWM
Threshold Current vs. VIN.
2010-2016 Microchip Technology Inc.
FIGURE 2-18:
High Load Waveforms.
DS40001420D-page 7
MCP1623/24
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.
FIGURE 2-19:
3.3V Start-Up after Enable.
FIGURE 2-22:
MCP1623 3.3V VOUT Load
Transient Waveforms.
MCP1623 PWM
FIGURE 2-20:
VIN = VENABLE.
3.3V Start-Up when
FIGURE 2-21:
MCP1624 3.3V VOUT Load
Transient Waveforms.
DS40001420D-page 8
FIGURE 2-23:
MCP1623 2.0V VOUT Load
Transient Waveforms.
FIGURE 2-24:
Waveforms.
3.3V VOUT Line Transient
2010-2016 Microchip Technology Inc.
MCP1623/24
3.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
PIN FUNCTION TABLE
MCP1623/24
Symbol
3.1
2x3 DFN
1
5
SW
2
—
GND
3
4
EN
Enable Control Input Pin
4
1
FB
Feedback Voltage Pin
5
—
VOUT
6
8
VIN
Input Voltage Pin
—
2
SGND
Signal Ground Pin
—
3
PGND
Power Ground Pin
—
7
VOUTS
Output Voltage Sense Pin
—
6
VOUTP
Output Voltage Power Pin
—
9
EP
Switch Node Pin (SW)
Connects the inductor from the input voltage to the SW
pin. The SW pin carries inductor current and can be as
high as 425 mA peak. The integrated N-Channel switch
drain and integrated P-Channel switch source are
internally connected at the SW node.
3.2
Ground Pin (GND)
The ground or return pin is used for circuit ground
connection. Length of trace from input cap return, output
cap return and GND pin should be made as short as
possible to minimize noise on the GND pin.
3.3
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 (greater than 90% of VIN)
will enable the regulator output. A logic low (less than
20% of VIN) will ensure that the regulator is disabled.
3.4
Feedback Voltage Pin (FB)
The FB pin is used to provide output voltage regulation
by using a resistor divider. The FB voltage will be 1.21V
typical with the output voltage in regulation.
3.5
Description
SOT-23
Output Voltage Pin (VOUT)
The output voltage pin connects the integrated
P-Channel MOSFET to the output capacitor. The FB
voltage divider is also connected to the VOUT pin for
voltage regulation.
2010-2016 Microchip Technology Inc.
Switch Node, Boost Inductor Input Pin
Ground Pin
Output Voltage Pin
Exposed Thermal Pad (EP); must be connected to VSS.
3.6
Power Supply Input Voltage Pin
(VIN)
Connects the input voltage source to VIN. The input
source should be decoupled to GND with a 4.7 µF
minimum capacitor.
3.7
Signal Ground Pin (SGND)
The signal ground pin is used as a return for the
integrated VREF and error amplifier. In the 2x3 DFN
package, the SGND and power ground (PGND) pins are
connected externally.
3.8
Power Ground Pin (PGND)
The power ground pin is used as a return for the
high--current N-Channel switch. In the 2x3 DFN
package, the PGND and signal ground (SGND) pins are
connected externally.
3.9
Output Voltage Sense Pin (VOUTS)
The output voltage sense pin connects the regulated
output voltage to the internal bias circuits. In the
2x3 DFN package, VOUTS and VOUTP are connected
externally.
3.10
Output Voltage Power Pin (VOUTP)
The output voltage power pin connects the output
voltage to the switch node. High current flows through
the integrated P-Channel and out of this pin to the
output capacitor and output. In the 2x3 DFN package,
VOUTS and VOUTP are connected externally.
3.11
Exposed Thermal Pad (EP)
There is an internal electrical connection between the
Exposed Thermal Pad (EP) and the VSS pin; they must
be connected to the same potential on the Printed
Circuit Board (PCB).
DS40001420D-page 9
MCP1623/24
NOTES:
DS40001420D-page 10
2010-2016 Microchip Technology Inc.
MCP1623/24
4.0
DETAILED DESCRIPTION
4.1
Device Option Overview
The MCP1623/24 family of devices is capable of low
start-up voltage and delivers high efficiency over a wide
load range for single-cell, two-cell, three-cell alkaline,
NiMH, NiCd and single-cell Li-Ion battery inputs. A high
level of integration lowers total system cost, eases
implementation and reduces board area. The devices
feature low start-up voltage, adjustable output voltage,
PWM/PFM mode operation, low IQ, integrated
synchronous switch, internal compensation, low noise
anti-ringing control, inrush current limit and soft start.
There is one feature option for the MCP1623/24 family:
PWM/PFM mode or PWM mode only.
4.1.1
PWM/PFM MODE OPTION
The MCP1624 devices use an automatic switchover
from PWM to PFM mode for light load conditions to
maximize efficiency over a wide range of output current.
During PFM mode, higher peak current is used to pump
the output up to the threshold limit. While operating in
PFM or PWM mode, the P-Channel switch is used as a
synchronous rectifier, turning off when the inductor
current reaches 0 mA to maximize efficiency. In PFM
mode, a comparator is used to terminate switching when
the output voltage reaches the upper threshold limit.
Once switching has terminated, the output voltage will
decay or coast down. During this period, very low IQ is
consumed from the device and input source, which
keeps power efficiency high at light load. The
disadvantages of PWM/PFM mode are higher output
ripple voltage and variable PFM mode frequency. The
PFM mode frequency is a function of input voltage,
output voltage and load. While in PFM mode, the boost
converter pumps the output up at a switching frequency
of 500 kHz.
2010-2016 Microchip Technology Inc.
4.1.2
PWM MODE ONLY OPTION
The MCP1623 devices disable PFM mode switching,
and operate only in PWM mode over the entire load
range. During periods of light load operation, the
MCP1623 continues to operate at a constant 500 kHz
switching frequency, keeping the output ripple voltage
lower than PFM mode. During PWM-only mode, the
MCP1623 P-Channel switch acts as a synchronous
rectifier by turning off to prevent reverse current flow
from the output cap back to the input in order to keep
efficiency high. For noise immunity, the N-Channel
MOSFET current sense is blanked for approximately
100 ns. With a typical minimum duty cycle of 100 ns,
the MCP1623 continues to switch at a constant
frequency under light load conditions. Figure 2-12
represents the input voltage versus load current for the
pulse-skipping threshold in PWM-only mode. At lighter
loads, the MCP1623 device begins to skip pulses.
TABLE 4-1:
Part Number
PART NUMBER SELECTION
PWM/PFM
MCP1623
MCP1624
PWM
X
X
DS40001420D-page 11
MCP1623/24
4.2
Functional Description
During this time, the boost switch current is limited to
50% of its nominal value. Once the output voltage
reaches 1.6V, normal closed-loop PWM operation is
initiated.
The MCP1623/24 charges an internal capacitor with a
very weak current source. The voltage on this
capacitor, in turn, slowly ramps the current limit of the
boost switch to its nominal value. The soft-start
capacitor is completely discharged in the event of a
commanded shutdown or a thermal shutdown.
There is no undervoltage lockout feature for the
MCP1623/24. The device will start up at the lowest
possible voltage and run down to the lowest possible
voltage. For typical battery applications, this may result
in “motor-boating” for deeply discharged batteries.
The MCP1623/24 is a compact, high-efficiency,
fixed-frequency, step-up DC-DC converter that
provides an easy-to-use power supply solution for
PIC® microcontroller applications powered by either
single-cell, two-cell, or three-cell alkaline, NiCd, or
NiMH, and single-cell Li-Ion or Li-Polymer batteries.
Figure 4-1 depicts the functional block diagram of the
MCP1623/24.
4.2.1
LOW-VOLTAGE START-UP
The MCP1623/24 is capable of starting from a low input
voltage. Start-up voltage is typically 0.65V for a 3.3V
output and 1 mA resistive load.
When enabled, the internal start-up logic turns the
rectifying P-Channel switch on until the output
capacitor is charged to a value close to the input
voltage. The rectifying switch is current limited during
this time. After charging the output capacitor to the
input voltage, the device starts switching. If the input
voltage is below 1.6V, the device runs open-loop with a
fixed duty cycle of 70% until the output reaches 1.6V.
VOUT
VIN
Internal
Bias
IZERO
Direction
Control
SW
EN
GND
0.3V
Gate Drive
and
Shutdown
Control
Logic
Oscillator
Soft Start
0V
ILIMIT
ISENSE
Slope
Comp.
S
PWM/PFM
Logic
1.21V
FB
EA
FIGURE 4-1:
DS40001420D-page 12
MCP1623/24 Block Diagram.
2010-2016 Microchip Technology Inc.
MCP1623/24
4.2.2
PWM MODE OPERATION
In normal PWM operation, the MCP1623/24 operates
as a fixed frequency, synchronous boost converter. The
switching frequency is internally maintained with a
oscillator typically set to 500 kHz. The MCP1623
device will operate in PWM-only mode even during
periods of light load operation. By operating in
PWM-only mode, the output ripple remains low and the
frequency is constant. Operating in fixed PWM mode
results in lower efficiency during light load operation
(when compared to PFM mode (MCP1624)).
Lossless current sensing converts the peak current
signal to a voltage to sum with the internal slope
compensation. This summed signal is compared to the
voltage error amplifier output to provide a peak current
control command for the PWM signal. The slope
compensation is adaptive to the input and output
voltage. Therefore, the converter provides the proper
amount of slope compensation to ensure stability, but is
not excessive, which causes a loss of phase margin.
The peak current limit is set to 425 mA typical.
4.2.3
PFM MODE OPERATION
The MCP1624 device is capable of operating in normal
PWM mode and PFM mode to maintain high efficiency
at all loads. In PFM mode, the output ripple has a
variable frequency component that changes with the
input voltage and output current. With no load, the
quiescent current draw from the output is typically
19 µA. The PFM mode can be disabled in selected
device options.
PFM operation is initiated if the output load current falls
below an internally programmed threshold. The output
voltage is continuously monitored. When the output
voltage drops below its nominal value, PFM operation
pulses one or several times to bring the output back
into regulation. If the output load current rises above
the upper threshold, the MCP1624 transitions smoothly
into PWM mode.
4.2.4
ADJUSTABLE OUTPUT VOLTAGE
The MCP1623/24 devices incorporate a true output
disconnect feature. With the EN pin pulled low, the
output of the MCP1623/24 is isolated or disconnected
from the input by turning off the integrated P-Channel
switch and removing the switch bulk diode connection.
This removes the DC path typical in boost converters,
which allows the output to be disconnected from the
input. During this mode, less than 1 µA of current is
consumed from the input (battery). True output disconnect does not discharge the output; the output voltage
is held up by the external COUT capacitance.
4.2.6
INTERNAL BIAS
The MCP1623/24 gets its start-up bias from VIN. Once
the output exceeds the input, bias comes from the
output. Therefore, once started, operation is
completely independent of VIN. Operation is only
limited by the output power level and the input source
series resistance. Once started, the output will remain
in regulation down to 0.35V typical with 1 mA output
current for low source impedance inputs.
4.2.7
INTERNAL COMPENSATION
The error amplifier, with its associated compensation
network, completes the closed-loop system by
comparing the output voltage to a reference at the
input of the error amplifier, and feeding the amplified
and inverted signal to the control input of the inner
current loop. The compensation network provides
phase leads and lags at appropriate frequencies to
cancel excessive phase lags and leads of the power
circuit. All necessary compensation components and
slope compensation are integrated.
4.2.8
SHORT-CIRCUIT PROTECTION
Unlike most boost converters, the MCP1623/24 allows
its output to be shorted during normal operation. The
internal current limit and overtemperature protection limit
excessive stress and protect the device during periods
of short circuit, overcurrent and overtemperature.
4.2.9
LOW-NOISE OPERATION
The MCP1623/24 output voltage is adjustable with a
resistor divider over a 2.0V minimum to 5.5V maximum
range. High-value resistors are recommended to
minimize quiescent current to keep efficiency high at
light loads.
The MCP1623/24 integrates a low-noise anti-ringing
switch that damps the oscillations typically observed at
the switch node of a boost converter when operating in
the Discontinuous Inductor Current mode. This
removes the high-frequency radiated noise.
4.2.5
4.2.10
ENABLE/OUTPUT DISCONNECT
The enable pin is used to turn the boost converter on
and off. The enable threshold voltage varies with input
voltage. To enable the boost converter, the EN voltage
level must be greater than 90% of the VIN voltage. To
disable the boost converter, the EN voltage must be
less than 20% of the VIN voltage.
2010-2016 Microchip Technology Inc.
OVERTEMPERATURE
PROTECTION
Overtemperature protection circuitry is integrated in the
MCP1623/24. This circuitry monitors the device junction
temperature and shuts the device off if the junction
temperature exceeds the typical +150oC threshold. If
this threshold is exceeded, the device will automatically
restart once the junction temperature drops by 10oC.
The soft start is reset during an overtemperature
condition.
DS40001420D-page 13
MCP1623/24
NOTES:
DS40001420D-page 14
2010-2016 Microchip Technology Inc.
MCP1623/24
5.0
APPLICATION INFORMATION
5.1
Typical Applications
The MCP1623/24 synchronous boost regulator
operates over a wide input voltage and output voltage
range. The power efficiency is high for several decades
of load range. Output current capability increases with
input voltage and decreases with increasing output
voltage. The maximum output current is based on the
N-Channel peak current limit. Typical characterization
curves in this data sheet are presented to display the
typical output current capability.
5.2
Adjustable Output Voltage
Calculations
To calculate the resistor divider values for the
MCP1623/24, Equation 5-1 can be used, where RTOP
is connected to VOUT, RBOT is connected to GND and
both are connected to the FB input pin.
EQUATION 5-1:
V OUT
R TOP = 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:
5.3
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 most applications,
4.7 µF of capacitance is sufficient at the input. For
high-power applications that have high source
impedance or long leads, connecting 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.
5.4
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.
The MCP1623/24 is internally compensated so output
capacitance range is limited. See Table 5-1 for the
recommended output capacitor range.
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.
EQUATION 5-2:
dV
I OUT = C OUT -------
dt
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 resistor divider that effect
the output voltage. The FB input leakage current can
also impact the divider and change the output voltage
tolerance.
Where:
dV = ripple voltage
dt = On time of the N-Channel switch
(D x 1/FSW)
Table 5-1 contains the recommended range for the
input and output capacitor value.
TABLE 5-1:
2010-2016 Microchip Technology Inc.
CAPACITOR VALUE RANGE
CIN
COUT
Min.
4.7 µF
10 µF
Max.
—
100 µF
DS40001420D-page 15
MCP1623/24
5.5
Inductor Selection
5.6
The MCP1623/24 is designed to be used with small
surface-mount inductors; the inductance value can
range from 2.2 µH to 10 µH. An inductance value of
4.7 µH is recommended to achieve a good balance
between inductor size, converter load transient
response and minimized noise.
ISAT
(A)
Part Number
DCR
(typ)
MCP1623/24
RECOMMENDED INDUCTORS
Value
(µH)
TABLE 5-2:
Size
WxLxH
(mm)
Thermal Calculations
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 MCP1623/24 is
+125oC.
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:
Coilcraft
ME3220
4.7
0.190
1.5
2.5x3.2x2.0
LPS3015
4.7
0.200
1.2
3.0x3.0x1.5
EPL3012
4.7
0.165
1.0
3.0x3.0x1.3
XPL2010
4.7
0.336
0.75
1.9x2.0x1.0
SD3110
4.7
0.285
0.68
3.1x3.1x1.0
SD3112
4.7
0.246
0.80
3.1x3.1x1.2
SD3114
4.7
0.251
1.14
3.1x3.1x1.4
Coiltronics®
Wurth Elektronik®
WE-TPC Type TH
4.7
0.200
0.8
2.8x2.8x1.35
WE-TPC Type S
4.7
0.105
0.90
3.8x3.8x1.65
WE-TPC Type M
4.7
0.082
1.65
4.8x4.8x1.8
0.70
2.3x2.3x1.0
Sumida Corporation
CMH23
4.7
0.537
CMD4D06
4.7
0.216
0.75
3.5x4.3x0.8
CDRH4D
4.7
0.09
0.800
4.6x4.6x1.5
B82462A2472M000
4.7
0.084
2.00
6.0x6.0x2.5
B82462G4472M
4.7
0.04
1.8
6.3x6.3x3.0
OUT I OUT
V
------------------------------ – V OUT I OUT = P Dis
Efficiency
The difference between the first term, input power, and
the second term, power delivered, is the internal
MCP1623/24 power dissipation. This is an estimate
assuming that most of the power lost is internal to the
MCP1623/24 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.
TDK Corporation
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.
Peak current is the maximum or limit, and 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.
DS40001420D-page 16
2010-2016 Microchip Technology Inc.
MCP1623/24
5.7
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 MCP1623/24 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.
Via to GND Plane
RBOT RTOP
+VIN
+VOUT
L
CIN
MCP1623/24
1
GND
FIGURE 5-1:
COUT
GND
Via for Enable
MCP1623/24 SOT-23-6 Recommended Layout.
2010-2016 Microchip Technology Inc.
DS40001420D-page 17
MCP1623/24
NOTES:
DS40001420D-page 18
2010-2016 Microchip Technology Inc.
MCP1623/24
6.0
PACKAGING INFORMATION
6.1
Package Marking Information (Not to Scale)
6-Lead SOT-23
Example
Part Number
Code
MCP1623T-I/CHY
HUNN
MCP1623T-I/CH
JANN
MCP1623T-I/CH
JUNN
MCP1624T-I/CHY
CJNN
MCP1624T-I/CH
JTNN
8-Lead DFN (2x3x0.9 mm)
Example
Part Number
Legend: XX...X
Y
YY
WW
NNN
e3
*
Note:
CJNN
Code
MCP1623-I/MC
AKH
MCP1623T-I/MC
AKH
MCP1624-I/MC
ALH
MCP1624T-I/MC
ALH
AKH
611
25
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 e( 3 )
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.
2010-2016 Microchip Technology Inc.
DS40001420D-page 19
MCP1623/24
6-Lead Plastic Small Outline Transistor (CHY) [SOT-23]
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
b
4
N
E
E1
PIN 1 ID BY
LASER MARK
1
2
3
e
e1
D
A
A2
c
φ
L
A1
L1
Units
Dimension Limits
Number of Pins
MILLIMETERS
MIN
N
NOM
MAX
6
Pitch
e
0.95 BSC
Outside Lead Pitch
e1
1.90 BSC
Overall Height
A
0.90
–
Molded Package Thickness
A2
0.89
–
1.45
1.30
Standoff
A1
0.00
–
0.15
Overall Width
E
2.20
–
3.20
Molded Package Width
E1
1.30
–
1.80
Overall Length
D
2.70
–
3.10
Foot Length
L
0.10
–
0.60
Footprint
L1
0.35
–
0.80
Foot Angle
I
0°
–
30°
Lead Thickness
c
0.08
–
0.26
Lead Width
b
0.20
–
0.51
Notes:
1. Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.127 mm per side.
2. Dimensioning and tolerancing per ASME Y14.5M.
BSC: Basic Dimension. Theoretically exact value shown without tolerances.
Microchip Technology Drawing C04-028B
DS40001420D-page 20
2010-2016 Microchip Technology Inc.
MCP1623/24
6-Lead Plastic Small Outline Transistor (CHY) [SOT-23]
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
2010-2016 Microchip Technology Inc.
DS40001420D-page 21
MCP1623/24
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