Application Notes

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PT6920/PT6930 Series

Using the Standby Function on the PT6920 and

PT6930 Dual Output Voltage Converters

Both output voltages of the 23-pin PT6920/6930 dual

output converter may be disabled using the regulator’s

standby function. This function may be used in applications

that require power-up/shutdown sequencing, or wherever

there is a requirement to control the output voltage On/

Off status with external circuitry.

The standby function is provided by the STBY* control

(pin 3). If pin 3 is left open-circuit the regulator operates

both regulator outputs will be simultaneously disabled and

the input current drawn by the ISR will typcially drop to

less than 30mA (50mA max). The standby control may also

be used to hold-off both regulator outputs during the pe-

riod that input power is applied.

The standby pin is ideally controlled using an open-collector

(or open-drain) discrete transistor (See Figure 1). It may

gate. Table 1 provides details of the threshold requirements.

Parameter

Min

Max

Enable (VIH)

1.8V

Vin

Disable (VIL)

–0.1V

0.8V

Notes:

1. The Standby/Inhibit control logic is similar for all

Power Trends’ modules, but the flexibility and

threshold tolerances will be different. For specific

information on this function for other regulator

models, consult the applicable application note.

2. The Standby control pin is ideally controlled using an

open-collector (or open-drain) discrete transistor and

requires no external pull-up resistor. To disable the

regulator output, the control pin must be pulled to

less than 0.8Vdc with a low-level 0.5mA sink to

ground.

3. The Standby input on the PT6920/6930 series may

be driven by a differential output device, making it

directly compatible with TTL logic. The control

A voltage of 1.8V or greater ensures that the

regulator is enabled. Do not use devices that can drive

Figure 1

Turn-On Time:

voltage signal at pin 3 and enables both outputs from the

PT6920/6930 regulator. Following a delay of about 10–20ms,

outputs reach full regulation voltage. The total power-up

time is less than 25ms, and is relatively independant of load,

temperature, and output capacitance. Figure 2 shows wave-

Figure 2

C

1

+

C

2

+

Inhibit

V

in

V

COM

COM

Q1

BSS138

+5V V

in

PT6921

18 - 21

23

7 - 11

4,5,6

Vin

V2

out

GND

Vo

V

1

16

V0

12 - 15

V1

out

V

22

STBY

3

V

C

3

+

Vo1 (3.3V)

Vo2 (2.5V)

Vstby

Ch1 1V/Div

Ch2 1V/Div

Ch3 5V/Div

Timebase: 5ms/Div

Not Recommended For New Designs