JAJSDU6A August 2017 – February 2019 TPS65919-Q1
PRODUCTION DATA.
Comparators that monitor the voltage on the VCC_SENSE, and VCCA pins control the power state machine of the TPS65919-Q1 device. For electrical parameters, see Section 4.12.
Figure 5-25 shows a block diagram of the system comparators and Figure 5-26 shows the state transitions.
NOTE
To generate a POR from a falling VCC, VCC is sampled every 1 ms and compared to the POR threshold. In case VCC is discharged and resupplied quickly, a POR may not be reliably generated if VCC crosses the POR threshold between samples. Another way to generate POR is to discharge the LDOVRTC regulator to 0 V after VCC is removed. With no external load, this could take seconds for the LDOVRTC output to discharge to 0 V. The PMIC should not be restarted after VCC is removed but before LDOVRTC is discharged to 0 V. If necessary, TI recommends adding a pulldown resistor from the LDOVRTC output to GND with a minimum of 3.9 kΩ to speed up the LDOVRTC discharge time.
The value of the pulldown resistor should be chosen based on the desired discharge time and acceptable current draw in the OFF state, but no greater than 0.5 mA. Use Equation 7 to calculate the pulldown resistor based on the desired discharge time.
where
Because LDOVRTC is always on when VCC is supplied, additional current is drawn through the pulldown resistor. The output current of LDOVRTC while the PMIC is in OFF state should not exceed 0.5 mA. Use Equation 8 to calculate the pulldown current.
where
To use comparators in the system:
Figure 5-27 shows more details on VSYS_MON comparator. When the VSYS_MON comparator is enabled, and the internal buffer is bypassed, the input impedance at VCC_SENSE pin is 500 kΩ (typical). When the comparator is disabled, the VCC_SENSE pin is in the high-impedance state. If GPADC is enabled to measure channel 2 or channel 3, 40 kΩ is added in parallel to the corresponding comparator. See Table 5-9 for GPADC input range.
To enable system voltage sensing above 5.25 V, an external resistive divider can be used. Internal buffers can be enabled by setting the OTP bit HIGH_VCC_SENSE to 1 to provide high impedance for the external resistive dividers. The maximum input level for the internal buffer is VCCA – 1 V.