JAJSOQ1 October 2023 TPS1210-Q1
ADVANCE INFORMATION
For limiting inrush current during turn-ON of the external FET (Q1) with capacitive loads, use R1, R2, C1 as shown in Figure 9-4. The R1 and C1 components slow down the voltage ramp rate at the gate of Q1 FET. The FET source follows the gate voltage resulting in a controlled voltage ramp across the output capacitors.
Use the Equation 2 to calculate the inrush current during turn-ON of the FET.
Where,
CLOAD is the load capacitance.
VBATT is the input voltage and Tcharge is the charge time.
V(BST-SRC) is the charge pump voltage (11 V),
Use a damping resistor R2 (approximately 10 Ω) in series with C1. Equation 3 can be used to compute required C1 value for a target inrush current. A 100-kΩ resistor for R1 can be a good starting point for calculations.
Connecting G1PD pin of TPS1210x-Q1 directly to the gate of the Q1 FET ensures fast turn-OFF without any impact of R1 and C1 components.
C1 results in an additional loading on CBST to charge during turn-ON. Use below equation to calculate the required CBST value:
Where,
Qg(total) is the total gate charge of the FET,
ΔVBST (1 V typical) is the ripple voltage across BST to SRC pins.