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iP1201

iP1201 Users Design Guidelines

The iP1201 can be configured as a dual channel

15A or parallel single 30A power block consisting of

optimized power semiconductors, PWM control and

its associated passive components. It is based on

a synchronous buck topology and offers an optimized

solution where space, efficiency and noise caused

by parasitics are of concern. The phase shifted, two

output power block operates with fixed frequency

voltage mode control and can be configured to oper-

ate as a dual output or paralleled single output with

current sharing. The iP1201 components are inte-

grated in a ball grid array (BGA) package.

The input operating voltage range of the iP1201 is

3.14V to 5.5V. Both channels of the power block have

a common input.

For applications where the input bus voltage is less

than 3.5V, A and B pins should be shorted. For input

voltages greater than 3.5V, A and B pins should be

disconnected and floating. Voltages at A and B pins

are internally generated, no external voltage source

should be connected to either one of these pins. A

Power-On-Reset is performed when V

IN falls below

2.5V.

Enabling the Outputs

The ENABLE pin turns on and turns off both outputs

of the iP1201 simultaneously. The iP1201 outputs

will be turned off by pulling the ENABLE pin to V

IN.

ENABLE low will start the outputs. The converter can

also be shutdown by pulling the soft-start pins to

PGND through a logic level MOSFET the drain of

which connects to the soft start pin (see Fig.14).

This feature can be useful if sequencing or different

start-up timing of the outputs are required. In situa-

tions where the output has undergone a latched shut-

down due to overvoltage or overcurrent, cycling

ENABLE will reset the outputs. Cycling soft start pins

will not unlatch the outputs.

Dual Soft Start

The Soft Start function provides a controlled rise of

the output voltage, thus limiting the inrush current

during start-up. The iP1201 provides two indepen-

dent soft start functions. The soft start pins can be

connected to the soft start capacitors to provide

Fig. 14: Soft Start/Enable Circuit

different start-up and sequencing profiles.

Each soft start function has an internal 25uA +/-20%

current source that charges the external soft start

capacitor C

ss up to 3V. During power-up, the output

voltage starts ramping up only after the charging

voltage across the C

ss capacitor has reached a

0.8Vtyp threshold, as shown in Fig. 15.

Fig. 15: Power Up Threshold

This threshold voltage should be taken into consid-

eration when designing sequencing profiles using

the iP1201 as it will effect start-up delays and ramp-

times.

To ensure complete discharge of the soft start ca-

pacitor C

ss, it is recommended to add a 1MΩ resis-

tor directly across C

ss.

For proper implementation of sequencing of out-

puts using the iP1201, refer to IR Application Note

AN-1053 - Power sequencing techniques using

iP1201 and iP1202.

Css

Iss

iP1201

SS1/SS2

0.8Vtyp

VCss

VOUT

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