ZHCSI09S June 2010 – August 2018 TPS65911
The TPS65911 device has three comparators for system status detection/control. One comparator detects the voltage at pin VCC7. When VCC7 > VMBHI, the comparator initiates a NO SUPPLY-to-OFF transition and the VMBHI_IT interrupt is generated. When VCC7 < VMBLO, the comparator initiates an ACTIVE/SLEEP/OFF-to-BACKUP transition. When both VCC7 and backup battery are below VBPNR, the device goes to the NO SUPPLY state.
Comparators COMP1 and COMP2 detect the voltage of VCCS. Programmable comparator COMP1 is intended for detecting if battery voltage is high enough for an OFF-to-ACTIVE transition of the TPS65911 device. For an OFF-to-ACTIVE transition VCCS must be > VMBCH (primary battery charged) and a level below the comparator threshold prevents the power-up sequence. The threshold can be set from 2.5 to 3.5 V with 50-mV steps through VMBCH_SEL. The comparator has debouncing so that VCCS must stay above VMBDCH (VMBCH – 0.1 V) for a debouncing period of 61 µs. The comparator can be bypassed if the threshold selection is set to 0. The default threshold is set in the boot configuration.
In a system with a multiple-cell battery, the battery level is sensed through an external resistor divider. The TPS65911 device has an internal buffer at the VCCS input, which must be used with the external resistive divider.
In a single-cell system, VCCS and VCC7 are connected directly to the battery. The VCCS input buffer can be bypassed to minimize power consumption. The buffer bypass is controlled with the VMBBUF_BYPASS bit in the boot configuration.
COMP2 is disabled by default and can be enabled by software. The comparator trigger generates an interrupt which is programmable on the rising (VMBCH2_H_IT) or falling edge (VMBCH2_L_IT), hence the comparator can be used for detecting high or low battery scenarios. COMP2 generates an interrupt for the host. In sleep mode, this creates a wake-up interrupt for the host. In off mode, the comparator trigger generates a turnon event. In backup or no supply modes, the comparator is not active.
The COMP2 threshold can be set from 2.5 to 3.5 V with 50-mV steps. Enabling the comparator is done through the voltage threshold selection bit VMBDCH2_SEL, which is set to 0 by default.