Microchip Technology MCP1631RD-MCC2 Data Sheet
© 2008 Microchip Technology Inc.
DS22063B-page 17
MCP1631/HV/MCP1631V/VHV
4.0
DETAILED DESCRIPTION
4.1
Device Overview
The MCP1631/MCP1631V device family combines the
analog functions to develop high frequency switch
mode power systems while integrating features for
battery charger and LED current source applications.
With the integration of a MOSFET driver, voltage
sense, current sense and over voltage protection, the
MCP1631/MCP1631V is a highly integrated, high-
speed analog pulse width modulator.
The MCP1631/MCP1631V output (V
analog functions to develop high frequency switch
mode power systems while integrating features for
battery charger and LED current source applications.
With the integration of a MOSFET driver, voltage
sense, current sense and over voltage protection, the
MCP1631/MCP1631V is a highly integrated, high-
speed analog pulse width modulator.
The MCP1631/MCP1631V output (V
EXT
) is used to
control the switch of the power system (on and off
time). By controlling the switch on and off time, the
power system output can be regulated. With the
oscillator and reference voltage as inputs, a simple
interface to a microcontroller is available with the
MCP1631/MCP1631V to develop intelligent power
systems. A good example of an intelligent power
system is a battery charger, programmable LED driver
current source or programmable power supply.
The MCP1631/MCP1631V is a combination of
specialty analog blocks consisting of a Pulse Width
Modulator (PWM), MOSFET Driver, Current Sense
Amplifier (A2), Voltage Sense Amplifier (A3),
Overvoltage Comparator (C2) and additional features
(Shutdown, Undervoltage Lockout, Overtemperature
Protection). For the HV options, an internal low dropout
regulator is integrated for operation from high voltage
inputs (MCP1631HV/MCP1631VHV).
time). By controlling the switch on and off time, the
power system output can be regulated. With the
oscillator and reference voltage as inputs, a simple
interface to a microcontroller is available with the
MCP1631/MCP1631V to develop intelligent power
systems. A good example of an intelligent power
system is a battery charger, programmable LED driver
current source or programmable power supply.
The MCP1631/MCP1631V is a combination of
specialty analog blocks consisting of a Pulse Width
Modulator (PWM), MOSFET Driver, Current Sense
Amplifier (A2), Voltage Sense Amplifier (A3),
Overvoltage Comparator (C2) and additional features
(Shutdown, Undervoltage Lockout, Overtemperature
Protection). For the HV options, an internal low dropout
regulator is integrated for operation from high voltage
inputs (MCP1631HV/MCP1631VHV).
4.2
Pulse Width Modulator (PWM)
The internal PWM of the MCP1631/MCP1631V is
comprised of an error amplifier, high-speed comparator
and latch. The output of the amplifier is compared to
either the MCP1631 CS (primary current sense input)
or the MCP1631V V
comprised of an error amplifier, high-speed comparator
and latch. The output of the amplifier is compared to
either the MCP1631 CS (primary current sense input)
or the MCP1631V V
RAMP
(voltage mode ramp input) of
the high speed comparator. When the CS or VRAMP
signal reach the level of the error amplifier output, the
on cycle is terminated and the external switch is
latched off until the beginning of the next cycle (high to
low transition of OSC
signal reach the level of the error amplifier output, the
on cycle is terminated and the external switch is
latched off until the beginning of the next cycle (high to
low transition of OSC
IN
).
4.3
V
EXT
MOSFET Driver
The MCP1631/MCP1631V output can be used to drive
the external MOSFET directly for low side topology
applications. The V
the external MOSFET directly for low side topology
applications. The V
EXT
is capable of sourcing up to
700 mA and sinking up to 1A of current from a P
VDD
source of 5V. Typical output power using the V
EXT
output to directly drive the external MOSFET can
exceed 50W depending upon application and switching
frequency.
exceed 50W depending upon application and switching
frequency.
4.4
Current Sense Amplifier (A2)
The A2 current sense amplifier is used to sense current
in the secondary side of a SEPIC converter or
freewheeling current in a Buck converter. The inverting
amplifier has a built in voltage gain of ten with low offset
and high speed.
in the secondary side of a SEPIC converter or
freewheeling current in a Buck converter. The inverting
amplifier has a built in voltage gain of ten with low offset
and high speed.
4.5
Voltage Sense Amplifier (A3)
The A3 voltage sense amplifier is used to sense battery
voltage. In battery powered applications, it is important
to minimize the steady stage load current draw on the
battery. The voltage sense amplifier (A3) is used to
buffer a high impedance series divider used to reduce
the battery pack voltage to a level that can be read
using an analog to digital converter. The voltage sense
amplifier draws a very low quiescent current and
remains functional when the MCP1631/MCP1631V is
shutdown making it possible to read battery voltage
without turning on the charger.
voltage. In battery powered applications, it is important
to minimize the steady stage load current draw on the
battery. The voltage sense amplifier (A3) is used to
buffer a high impedance series divider used to reduce
the battery pack voltage to a level that can be read
using an analog to digital converter. The voltage sense
amplifier draws a very low quiescent current and
remains functional when the MCP1631/MCP1631V is
shutdown making it possible to read battery voltage
without turning on the charger.
4.6
Overvoltage Comparator(C2)
The C2 overvoltage comparator is used to prevent the
power system from being damaged when the load
(battery) is disconnected. By comparing the divided
down power train output voltage with a 1.2V internal
reference voltage, the MCP1631/MCP1631V V
power system from being damaged when the load
(battery) is disconnected. By comparing the divided
down power train output voltage with a 1.2V internal
reference voltage, the MCP1631/MCP1631V V
EXT
output switching is interrupted when the output voltage
is above a pre-set value. This limits the output voltage
of the power train, the 0V comparator’s hysteresis will
operate as a ripple regulator.
is above a pre-set value. This limits the output voltage
of the power train, the 0V comparator’s hysteresis will
operate as a ripple regulator.
4.7
Shutdown Input
The MCP1631/MCP1631V shutdown feature is used to
disable the device with the exception of the voltage
sense amplifier A3 to minimize quiescent current draw.
While shutdown, A3 remains operational while the
device draws 4.4 µA from the input.
disable the device with the exception of the voltage
sense amplifier A3 to minimize quiescent current draw.
While shutdown, A3 remains operational while the
device draws 4.4 µA from the input.
4.8
Protection
The MCP1631/MCP1631V has built in Undervoltage
Lockout (UVLO) that ensures the output V
Lockout (UVLO) that ensures the output V
EXT
pin is
forced to a known state (low) when the input voltage or
A
A
VDD
is below the specified value. This prevents the
main MOSFET switch from being turned on during a
power up or down sequence.
The MCP1631/MCP1631V provides a thermal
shutdown protection feature, if the internal junction
temperature of the device becomes high, the
overtemperature protection feature will disable (pull the
V
power up or down sequence.
The MCP1631/MCP1631V provides a thermal
shutdown protection feature, if the internal junction
temperature of the device becomes high, the
overtemperature protection feature will disable (pull the
V
EXT
output low) and shut down the power train.