The LP87702-Q1 device supports programmable start-up and shutdown sequencing. An enable control signal is used to initiate the start-up sequence and to turn off the device according to the programmed shutdown sequence. Up to three enable inputs are available: EN1 is a dedicated enable input; EN2 and EN3 are multiplexed with I2C interface. The buck converter is selected for sequence control with:

• BUCKx_CTRL_1(BUCKx_EN) = 1
• BUCKx_CTRL_1(BUCKx_EN_PIN_CTRL) = 0x1 or 0x2 or 0x3, for EN1 or EN2 or EN3 control, respectively
• BUCKx_VOUT.(BUCKx_VSET[7:0]) = Required voltage when EN pin is high
• The delay from rising edge of EN pin to the converter enable is set by BUCKx_DELAY(BUCKx_STARTUP_DELAY[3:0]) bits and
• The delay from falling edge of EN pin to the converter disable is set by BUCKx_DELAY(BUCKx_SHUTDOWN_DELAY[3:0])

In the same way the boost converter is selected for delayed control with:

• BOOST_CTRL(BOOST_EN) = 1
• BOOST_CTRL(BOOST_EN_PIN_CTRL) = 0x1 or 0x2 or 0x3, for EN1. EN2, or EN3 control (respectively)
• BOOST_CTRL(BOOST_VSET[2:0]) = Required voltage when EN pin is high
• The delay from rising edge of EN pin to the converter enable is set by BOOST_DELAY(BOOST_STARTUP_DELAY[3:0]) bits and
• The delay from falling edge of EN pin to the converter disable is set by BOOST_DELAY(BOOST_SHUTDOWN_DELAY[3:0])

An example of start-up and shutdown sequences for buck converters are shown in Figure 8-7. The start-up and shutdown delays for Buck0 converter are 1 ms and 4 ms and for Buck1 converter 3 ms and 1 ms. The delay settings are used only for enable or disable control with the EN signal.

Figure 8-7 Start-up and Shutdown Sequencing Example