STPMIC1DPQR datasheet(41/140 Pages) STMICROELECTRONICS

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Enable/disable – Boost can be enabled in POWER_ON state only by I2C setting of BST_ON bit in BST_SW_CR

Boost can be disabled by I2C clearing BST_ON bit.

Boost is also disabled during POWER_DOWN sequence in RANK0 slot and when overcurrent or overvoltage

condition is present for defined time.

Output discharge – When boost is switched off (BST_ON bit = ‘0’), switching stops immediately and a passive

discharge, enabled on BSTOUT by default, occurs.

Output discharge can be disabled by setting BST_PDbit in Table 29. LDO56_VREF_PD_CR register.

Overvoltage protection – Boost converter has an overvoltage protection. If voltage on BSTOUT pin exceeds

VBSTOVP threshold, LXB pin stops switching immediately, and remains in high impedance state. If the overvoltage

condition lasts for more than tOVPDB_BST, boost is disabled, and BST_OVP interrupt is generated.

OVP event on BSTOUT also disables switches PWR_USB_SW and PWR_SW (if NVM_SWOUT_BOOST_OVP

is set in Table 70. NVM_LDOS_VOUT_SHR1).

Overcurrent protection – Boost implements low-side current sensor with peak current detector (IBSTLIM), and

high-side current sensor with short-circuit detector, (IBSTSH). If the overcurrent condition during HS phase lasts for

more than tOCPDB_BST, boost is disabled, and BST_OCP interrupt is generated.

Start-up sequence Boost start-up sequence consists of 2 phases:

•

Precharge phase - in this phase, bypass switch operates in “constant current source” mode and charges

boost output capacitor with constant IPRECH_BST current for tPRECH_BST duration. After this time, boost

output voltage is checked. If VBSTOUT > VPRECH =~ (VIN – 0.7 V), boost starts switching and proceeds to

soft-start phase, besides boost is immediately turned off and BST_OCP interrupt is generated

Note:

Boost load during precharge phase must be minimized, from this reason it is necessary to enable

PWR_USB_SW and PWR_SW after the boost soft-start is finished.

•

Soft-start phase – in this phase boost switches, the inrush current minimizes. Soft-start duration is tSS_BST

Figure 49. Boost start-up sequence

4.5.2

PWR_USB_SW and PWR_SW power switches

PWR_USB_SW is a 500 mA power switch dedicated to supply a USB port (VBUS voltage) and it is compatible

with USB OTG specifications. PWR_USB_SW input is internally connected to boost converter output (BSTOUT).

See Figure 48. Boost and switch block diagram.

Reverse current protection - VBUSOTG pin is a switch with a reverse current protection to prevent leakage

from VBUSOTG pin to BSTOUT or VIN when switch is OFF.

STPMIC1

Boost converter and power switches

DS12792 - Rev 7

page 41/140

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