Application Notes

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PT4711

Figure 3-3; PT4711 Power-up Sequence

On/Off Output Voltage Sequencing

Both outputs from the PT4711 converter are internally

sequenced to power up in unison. Figure 3-3 shows the

output waveforms after the module’s output has been

enabled. The converter produces a fully regulated output

within 75 ms. The waveforms were measured with the

output voltages configured per Figure 1-1a (for ±15-V

output). A constant current load of 1.5 A was applied to

both outputs, with an input source of 48 VDC.

Using the On/Off Enable Controls on the PT4711

Dual-Output DC/DC Converter

The PT4711 is a dual-output DC/DC converter incor-

porates two output enable controls. EN1 (pin 4) is the

Negative Enable input, and EN2 (pin 3) is the Positive

Enable input. Both inputs are electrically referenced to

A pull-up resistor is not required, but may be added if

desired. Voltages of up to 70 V can be safely applied to

the either of the Enable pins.

Automatic (UVLO) Power-Up

(pin 3) open-circuit configures the converter for auto-

matic power up. (See data sheet “Typical Application”).

The converter control circuitry incorporates an “Under

Voltage Lockout” (UVLO) function, which disables the

converter until the minimum specified input voltage is

circuitry ensures a clean transition during power-up and

power-down, allowing the converter to tolerate a slow-

rising input voltage. For most applications EN1 and EN2,

can be configured for automatic power-up.

Positive Output Enable (Negative Inhibit)

To configure the converter for a positive enable function,

On/Off control signal to EN2 (pin 3). In this configura-

pin 3 disables the converter outputs. Figure 1 is an example

of this configuration.

Negative Output Enable (Positive Inhibit)

To configure the converter for a negative enable function,

EN2 (pin 3) is left open circuit, and the system On/Off

control signal is applied to EN1 (pin 4). A low-level

DC/DC

Module

EN 1*

EN 2

–Vin

–V

IN

1 =Outputs Off

3

4

2

BSS138

DC/DC

Module

EN 1*

EN 2

–Vin

–V

IN

1 =Outputs On

3

4

2

BSS138

Figure 2; Negative Enable Configuration

Figure 1; Positive Enable Configuration

pin 4 in order to enable the outputs of the converter.

An example of this configuration is detailed in Figure 2.

Note: The converter will only produce an output voltage if a

+Vo (5 V/Div)

1

+Vo (5 V/Div)

2

HORIZ SCALE: 5 ms/Div