A7985ATR datasheet(6/44 Pages) STMICROELECTRONICS

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Pin settings

A7985A

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DocID023128 Rev 5

Pin settings

1.1

Pin connection

Figure 2. Pin connection (top view)

1.2

Pin description

Table 1. Pin description

Type

Description

OUT

Regulator output.

SYNCH

Master/slave synchronization. When it is left floating, a signal with

a phase shift of half a period in respect to the power turn-on is present at

the pin. When connected to an external signal at a frequency higher than

the internal one, the device is synchronized by the external signal, with

zero phase shift.

Connecting together the SYNCH pins of two devices, the one with the

higher frequency works as master and the other as slave; so the two

power turn-ons have a phase shift of half a period.

3EN

A logical signal (active high) enables the device. With EN higher than

1.2 V the device is ON and with EN lower than 0.63 V the device is OFF.

COMP

Error amplifier output to be used for loop frequency compensation.

5FB

Feedback input. Connecting the output voltage directly to this pin the

output voltage is regulated at 0.6 V. To have higher regulated voltages an

external resistor divider is required from VOUT to the FB pin.

6FSW

The switching frequency can be increased connecting an external

resistor from the FSW pin and ground. If this pin is left floating the device

works at its free-running frequency of 250 KHz.

GND

Ground.

8VCC

Unregulated DC input voltage.

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