ZHCSQT8 October 2023 LM74930-Q1
PRODUCTION DATA
Programming the Overcurrent Protection Threshold – RILIM Selection
The RILIM sets the overcurrent protection (circuit breaker detection) threshold, whose value can be calculated using Equation 15.
To set 5 A as overcurrent protection threshold, RILIM value is calculated to be 120 kΩ. Choose available standard value: 120 k?, 1%.
Programming the Circuit Breaker Time – CTMR Selection
For the design example under discussion, overcurrent transients are allowed for 1-ms duration. This blanking interval, TOC (or circuit breaker interval, TCB) can be set by selecting appropriate capacitor CTMR from TMR pin to ground. The value of CTMR can be calculated using Equation 16.
CTMR value of 68 nF, 10% is selected to allow circuit breaker duration of close to 1-ms.
Programming Current Monitoring Output – RIMON Selection
Voltage at IMON pin VIMON is proportional to the output load current. This can be connected to an ADC of the downstream system for monitoring the operating condition and health of the system. The RIMON must be selected based on the maximum load current and the input voltage range of the ADC used. RIMON is set using Equation 17.
For this application example, VIMON is selected to be 2.7 V at full load current of 5 A. RIMON value of 30.1 k?, 1% is selected.