Application Notes

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PTH03050W

15

6

3

4

2

Track

GND

Inhibit

Adjust

PTH03050W

15

6

3

4

2

Track

GND

Inhibit

Adjust

R1

887

C3

100 µF

C4

100 µF

R2

2.21 k

R3

5.49 k

C1

100 µF

C2

100 µF

PTB78520W

+Sense

–Sense

Track

1

2

3

4

8

10

9

7

6

5

U1

U2

U3

Figure 2-2; Power-Up Sequencing Circuit With PTB78520W & Non-Isolated POL Modules

V Bus (1 V/Div)

o

V Seq (1 V/Div)

o

V

1 (1 V/Div)

POL

V

2 (1 V/Div)

POL

HORIZ SCALE: 20 ms/Div

t =20 ms

d

Figure 2-3; PTB78520 Power-Up Waveforms with POL Modules

Typical Power-Up Sequencing Configuration

configured to provide two 3.3 V sources, that allow it to

both power and sequence with one or more non-isolated

POL modules. The example shows two PTH03050W

Additional voltages, as well as modules with a higher

output current capability can also be specified to meet a

specific application. The number of downstream modules,

their respective output voltage and load current rating is

only limited by the amount of current available at the

The output voltage adjust range of the PTB78520W is

1.8 V to 3.6 V, which is compatible with the 3.3-V input

non-isolated POL modules. In these applications, the

PTB78520W output voltage must always be set to 3.3 V

age over the range, 0.8 V to 2.5 V. In this example they

respectively. Figure 2-3 shows the power-up waveforms

from Figure 2-2 when the Track control input to all three

modules are simply connected together.

The PTB78520W provides input power to the down-

This is the output that rises first to allow the down-

PTB78520W

stream modules to complete their power-up initialization.

(1.8 V), supply the load circuit. These three outputs

are controlled by the track control voltage, which the

PTB78520W holds at ground potential for 20 ms after

control voltage is finally allowed to rise, the three outputs

rise simultaneously to their respective set-point voltages.

Not Recommended for New Designs