MC33129 Просмотр технического описания (PDF) - Motorola => Freescale

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MC33129

High Performance Current Mode Controllers

Motorola => Freescale 

FreescalMeCS34e1m29iMcCo3n3d1u29ctor, Inc.

PIN FUNCTION DESCRIPTION

Pin

Function

Description

1

Drive Output

This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are

sourced and sinked by this pin.

2

Drive Ground

This pin is a separate power ground return that is connected back to the power source. It is

used to reduce the effects of switching transient noise on the control circuitry.

3

Ramp Input

A voltage proportional to the inductor current is connected to this input. The PWM uses this

information to terminate output switch conduction.

4

Sync/Inhibit Input

A rectangular waveform applied to this input will synchronize the Oscillator and limit the

maximum Drive Output duty cycle. A dc voltage within the range of 2.0 V to VCC will inhibit

the controller.

5

RT/CT

The free–running Oscillator frequency and maximum Drive Output duty cycle are

programmed by connecting resistor RT to Vref 2.5 V and capacitor CT to Ground. Operation

to 300 kHz is possible.

6

Vref 2.50 V

7

Ground

This output is derived from Vref 1.25 V. It provides charging current for capacitor CT through

resistor RT.

This pin is the control circuitry ground return and is connected back to the source ground.

8

Vref 1.25 V

This output furnishes a voltage reference for the Error Amplifier noninverting input.

9

Error Amp Noninverting Input This is the noninverting input of the Error Amplifier. It is normally connected to the 1.25 V

reference.

10

Error Amp Inverting Input

This is the inverting input of the Error Amplifier. It is normally connected to the switching

power supply output through a resistor divider.

11

Feedback/PWM Input

This pin is available for loop compensation. It is connected to the Error Amplifier and

Soft–Start Buffer outputs, and the Pulse Width Modulator input.

12

CSoft–Start

A capacitor CSoft–Start is connected from this pin to Ground for a controlled ramp–up of peak

inductor current during startup.

13

Start/Run Output

This output controls the state of an external bootstrap transistor. During the start mode,

operating bias is supplied by the transistor from Vin. In the run mode, the transistor is

switched off and bias is supplied by an auxiliary power transformer winding.

14

VCC

This pin is the positive supply of the control IC. The controller is functional over a minimum

VCC range of 4.2 V to 12 V.

MOTOROLA ANALOG IC DEVICEFDoArTMA ore Information On This Product,

7

Go to: www.freescale.com

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