I have selected the bq24040 for a new product.
I have been working on my prototypes and have found that, although the IC appears to properly handle charging of a battery, it is not passing power through when a battery is not present. My reading of the datasheet suggests that it should be doing so. I have even removed the thermistor (normally on the board, not with the battery) to force the device into TTDM mode.
I follow the schematic in the datasheet fairly closely. I'm using PG and CHG as inputs to a microcontroller instead of to drive LEDs. Preterm is floating, to accept the 10/20% defaults. I initially specified a 536 ohm resistor on ISET to set the charge current as close to 1 A as possible, but due to overheating problems I've been forced to increase this value.
The input to the above circuit is a micro USB type B connector for supplying 5 V to the system, and the output connects to the battery (+) terminal as well as the rest of the system. I have measured about 4.8 V on IN, which is well above the UVLO level.
