MCP1630 datasheet(9/18 Pages) MICROCHIP

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 2004 Microchip Technology Inc.

DS21896A-page 9

MCP1630

3.0

MCP1630 PIN DESCRIPTIONS

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

TABLE 3-1:

PIN FUNCTION TABLE

3.1

COMP Pin

COMP is an internal error amplifier output pin. External

compensation is connected from the FB pin to the

COMP pin for control-loop stabilization. An internal

voltage clamp is used to limit the maximum COMP pin

voltage to 2.7V typical. This clamp is used to set the

maximum peak current in the power system switch by

setting a maximum limit on the CS input for peak

current mode control systems.

3.2

FB Pin

FB is an 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 feed

back is used.

3.3

CS Input

CS is the current sense input pin used for cycle-by-

cycle control for peak current mode converters. A ramp

can be placed on this input for voltage or average

current mode converters.

3.4

OSC Input

OSC is an external oscillator input pin. Typically, a

microcontroller I/O pin is used to generate the OSC

input. When high, the output driver (VEXT) pin is driven

low. The high-to-low transition initiates the start of a

new cycle. The duty cycle of the OSC input pin deter-

mines the maximum duty cycle of the power converter.

For example, if the OSC input is low for 75% of the time

and high for 25% of the time, the duty cycle range for

the power converter is 0% to 75% maximum.

3.5

GND

Connect circuit ground to the GND pin. For most appli-

cations, this should be connected to the analog or quiet

ground plane. Noise on this ground can affect the

sensitive cycle-by-cycle comparison between the CS

input and the error amplifier output.

3.6

VEXT Pin

VEXT is an external driver output pin. This output pin is

used to determine the power system duty cycle. For

high-power or high-side drives, this output should be

connected to the logic-level input of the MOSFET driver.

For low-power, low-side applications, the VEXT pin can

be used to directly drive the gate of an N-channel

MOSFET.

3.7

VIN Pin

VIN is an input voltage pin. Connect the input voltage

source to the VIN pin. For normal operation, the voltage

on the VIN pin should be between +3.0V and +5.5V. A

0.1 µF bypass capacitor should be connected between

the VIN pin and the GND pin.

3.8

VREF Input

VREF is an external reference input pin used to regulate

the output of the power system. By changing the VREF

input, the output (voltage or current) of the power sys-

tem can be changed. The reference voltage can range

from 0V to VIN (rail to rail).

Pin No.

Name

Function

COMP

Error Amplifier Output Pin

Error Amplifier Inverting Input

Current Sense Input pin

OSC IN

Oscillator Input pin

GND

Circuit Ground Pin

6VEXT

External driver output pin

7VIN

Input bias pin

8VREF

Reference Voltage Input Pin

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