Datasheet

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TPS54283 , , TPS54286

SLUS749C – JULY 2007 – REVISED OCTOBER 2007

TERMINAL FUNCTIONS (continued)

TERMINAL

I/O DESCRIPTION

NAME NO.

This pin configures the output startup mode. If the SEQ pin is connected to BP, then when Output 2 is

enabled, Output 1 is allowed to start after Output 2 has reached regulation; that is, sequential startup

where Output 1 is slave to Output 2. If EN2 is allowed to go high after the outputs have been operating,

then both outputs are disabled immediately, and the output voltages decay according to the load that is

present. For this sequence configuration, tie EN1 to ground.

If the SEQ pin is connected to GND, then when Output 1 is enabled, Output 2 is allowed to start after

Output 1 has reached regulation; that is, sequential startup where Output 2 is slave to Output 1. If EN1

is allowed to go high after the outputs have been operating, then both outputs are disabled immediately,

SEQ 10 I

and the output voltages decay according to the load that is present. For this sequence configuration, tie

EN2 to ground.

If left floating, Output 1 and Output 2 start ratio-metrically when both outputs are enabled at the same

time. They soft start at a rate determined by their final output voltage and enter regulation at the same

time. If the EN1 and EN2 pins are allowed to operate independently, then the two outputs also operate

independently.

NOTE: An internal two resistor (150-k Ω each) divider connects BP to SEQ and to GND. See Table 1

Sequencing States.

Source (switching) output for Output 1 PWM. A snubber is recommended to reduce ringing on this

SW1 3 O

node. See SW Node Ringing for further information.

Source (switching) output for Output 2 PWM. A snubber is recommended to reduce ringing on this

SW2 12 O

node. See SW Node Ringing for further information.

Thermal Pad - - This pad must be tied externally to a ground plane and the GND pin.

Product Folder Link(s): TPS54283 TPS54286