JAJSOU3 March 2024 TPS1213-Q1
ADVANCE INFORMATION
In the applications where low power bypass path is not used, the cap charging can be done using main FET gate drive control.
For limiting inrush current during turn-ON of the main FET with capacitive loads, use R1, R2, C1 as shown in Figure 7-6. The R1 and C1 components slow down the voltage ramp rate at the gate of main FET. The FET source follows the gate voltage resulting in a controlled voltage ramp across the output capacitors.
Use the Equation 24 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 (~ 10 Ω) in series with C1. Equation 6 can be used to compute required C1 value for a target inrush current. A 100kΩ resistor for R1 can be a good starting point for calculations.
Connecting G1PD pin of TPS12130-Q1 directly to the gate of the external 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.