Marantz MAR775, MAR770, DR-6000 service manual Pin function description, Pin Name, Vcc

Pin function description

Pin

1

2

3

4

5

6

7

8

9

10

11

12

Name

VCC

VC

Output

Gnd

Foldback Input

Overvoltage

Protection

Current Sense Input

Demagnetisation Detection

Synchronisation Input

CT

Soft- Start/Dmax/Volta ge-Mode

RP Standby

Description

This pin is the positive supply of the IC. The operating voltage range after start-up is 9.0 to 14.5 V.

The output high state (VOH) is set by the voltage applied to this pin.

Peak currents up to 750 mA can be sourced or sunk, suitable for driving either MOSFET or bipolar transistors.

The groundpin is a single return, typically connected back to the power source.

The foldback function provides overload protection.

When the overvoltage protection pin receives a voltage greater than 2.5V, the device is disabled and requires a complete restart sequence.

A voltage proportional to the current flowing into the power switch is connected to this input.

A voltage delivered by an auxiliary transformer winding provides to the demagnetisation pin an indication of the magnetisation state of the flyback transformer. A zero voltage detection corresponds to complete core saturation.

The synchronisation input pin can be activated with either a negative pulse going from a level between 0.7V and 3.7V to Gnd or a positive pulse going from a level between 0.7V and 3.7V up to a level higher than 3.7V. The oscillator runs free when Pin 9 is connected to Gnd.

The normal mode oscillator frequency is programmed by the capacitor CT choice together with the Rref resistance value. CT, connected between Pin 10 and Gnd, generates the oscillator sawtooth.

A capacitor, resistor or a voltage source connected to this pin limits the switching duty-cycle. This pin can be used as a voltage mode control input. By connecting Pin 11 to Ground, the MC44603 can be shut down.

A voltage level applied to the RP Standby pin determines the output power level at which the oscillator will turn into the reduced frequency mode of operation (i.e. standby mode). An internal hysteresis comparator allows to return in the normal mode at a higher output power level.

13

14

15

16

E/A Out

Voltage Feedback

RF Standby

Rref

The error amplifier output is made available for loop compensation.

This is the inverting input of the Error Amplifier. It can be connected to the switching power supply output through an optical (or other) feedback loop.

The reduced frequency or standby frequency programming is made by the RF Standby resistance choice.

Rref sets the internal reference current. The internal reference current ranges from 100 A to 500 A. This requires that 5.0kW £ Rref £ 25kW .

CL 96532076_031.eps 290799

Figure 8-12

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