Datasheet

UCD9081

www.ti.com

SLVS813B –JUNE 2008–REVISED DECEMBER 2010

FUNCTIONAL DESCRIPTION

POWER SUPPLY SEQUENCING

The UCD9081 can be configured to sequence power supply rails using the enable signals (ENx) or the

general-purpose outputs (GPOx) in one of four ways:

1. A rail can be configured to not be sequenced

2. Using a delay time after UCD9081 RESET. The enable/GPO is asserted after UCD9081 RESET plus the

user specified delay

3. Using a delay time after another (parent) rail has achieved regulation (V

RAIL

is within specified under- and

overvoltage settings). The enable/GPO is asserted after the (parent) rail is in regulation plus the user

specified delay.

4. Using a (parent) rail voltage. The enable/GPO is asserted after the (parent) rail voltage is greater than or

equal to the user specified voltage.

POWER-SUPPLY ENABLES

The UCD9081 can sequence and enable/disable up to eight power supplies through the ENx (EN1 to EN8)

signals. These signals can be configured active-high or active-low, supporting power supplies with either polarity.

EN8 can also be configured as a GPO (GPO1). EN8/ADDR1/GPO1 is also used for I

C address selection

(ADDR1).

Note that while the UCD9081 is in RESET, the enable signals are in a high-impedance state. The enable signals

should be pulled up or down on the board according to the desired default power-supply state (enabled or

disabled).

GENERAL PURPOSE OUTPUTS

The UCD9081 can control up to four general-purpose digital outputs through the same sequencing mechanisms

as the power supply enables. These general-purpose outputs (GPO1–GPO4) can be used for digital signals such

as resets or status inputs to other devices. Note that these signals are multiplexed with other functions (primarily

C address selection). See the Terminal Functions table to ensure that these signals are used properly by the

application. Also note that the GPO1 signal is multiplexed with EN8.

C INTERFACE

The UCD9081 power-supply sequencer has a 100 kHz, slave mode I

C interface for communication with an I

master. The I

C master uses this interface to configure and monitor the UCD9081. Note that the master must

support clock stretching in order to properly communicate with the UCD9081.

Product Folder Link(s) :UCD9081