SLVSHM2B March 2025 – October 2026 TPS2HC120-Q1
PRODUCTION DATA
In the OFF state, when DIAG_EN is high, there is an internal pull-up resistor RPU that pulls up a channel to VBB. The specific channel that gets pulled up is based on the SEL pin, and the other channels do not have the pull-up resistor engaged.
If there is load present at the selected channel, then the output voltage is pulled to around 0V, as the load is much stronger than the RPU. In the case of an open load, the output voltage is pulled close to the supply voltage by the RPU. If VBB - VOUT < VOL,off for the selected channel, the FLT pin goes low to indicate the fault to the MCU, and the SNS pin is pulled up to ISNSFH.
The value of the internal pull-up resistor (RPU) can cause LED loads to flicker during the OFF state (when DIAG_EN in high). External pull-down resistors on the output channels and switchable pull-up resistor network resolves the observed flicker.
If the time constant due the RPU and output capacitor is too large for normal diagnosis timing, the DIAG_EN must be toggled longer for proper open-load detection.