Other Parts Discussed in Thread: MSP430G2353
Situation: VBAT = Li+ battery, single cell, 4.2V fully charged. TPS61020 boosts this to a 5V level.
1) Per the data sheet, the EN input requires a minimum of 0.8*Vbat.
How much leeway there is on the EN minimum high voltage, VIH. The reason I ask it that way is that the minimum EN voltage would be 3.36V (0.8*4.2) with a fully charged battery. The EN circuit is driven by a digital output (P1.7/CAOUT/UCB0SIMO/UCB0SDA/A7/CA7/TDO/TDI) of an MSP430G2353 that's power supply is a 3V. So, at the best
possible scenario, the EN circuit voltage from the MSP430 is <= 3V. So theoretically, with a fully charged battery, the EN pin would never reach a high enough voltage to EN the chip.
2) If the battery voltage is low (prior to being charged) such that the 0.8*Vbatt EN voltage is met by the MSP430, what happens as the battery voltage rises as the battery is charged. Will the EN circuit shut the TP61026 off once the 0.8*Vbatt requirement is no longer met. Or, once on, does the EN pin require the voltage to drop even more, ie, some hysteresis? If so, what is the it?