MCP1633 datasheet(13/31 Pages) MICROCHIP

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DS20006289A-page 13

MCP1633

3.0

PIN DESCRIPTION

The descriptions of the pins are listed in Table 3-1.

3.1

Switching Frequency Set (FSW)

The switching frequency is set by an external resistor

connected between the FSW pin and Ground. The

frequency can be adjusted between 200 kHz and

2.2 MHz.

3.2

Open-Drain Fault Indicator

(FAULT)

The open drain output provides an indication about

chip status. This output is active low and is triggered by

the input undervoltage, output overvoltage and over-

temperature.

3.3

Soft Start/Reference Voltage Set

(SS/Ref)

This pin is the output of the internal Constant Current

Generator (50 µA typical). An external resistor must be

connected between this pin and GND. The current

flowing in this resistor will set the reference voltage.

Optionally, a capacitor may also be connected between

this pin and GND to set the soft start ramp behavior.

This pin may be overdriven by an external voltage

source, enabling the reference voltage to be controlled

externally.

3.4

Error Amplifier Output (COMP)

COMP is the internal error amplifier output pin. External

compensation is connected from COMP to GND for

control-loop stabilization.

3.5

Inverting Error Amplifier Input

(FB)

FB is the internal error amplifier inverting input pin. The

output (voltage or current) is sensed and fed back to

the FB pin for regulation. Inverting or negative

feedback is used.

3.6

Current Sense Operational

Amplifier Output (IOUT)

This pin is connected to the current sense operational

amplifier output. It can be connected directly to the FB

pin to close the current loop or to a microcontroller to

measure the output current.

3.7

Current Sense Operational

Amplifier Positive Input (ISP)

This pin is directly connected to the noninverting input

of the current sense operational amplifier.

TABLE 3-1:

PIN FUNCTION TABLE

MCP1633

QFN16

Symbol

Description

1FSW

Switching Frequency Set

2FAULT

Open-Drain Fault Indicator

SS/VREF

Soft Start/Reference Voltage Set

COMP

Error Amplifier Output

Inverting Error Amplifier Input

6IOUT

Current Sense Operational Amplifier Output

ISP

Current Sense Operational Amplifier Positive Input

ISN

Current Sense Operational Amplifier Negative Input

CSO

Current Sense Offset

Current Sense Input

VEXT

PWM Output signal

VCC

Input Bias

SDRV

Series Dimming MOSFET Gate Driver Output

DIMM

PWM Dimming Input

OVP

Overvoltage Protection Input

EN/Sync

Enable or external synchronization input

Exposed Thermal Pad, Analog Ground and Power Ground

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