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ZHCSO49C May 2021 – March 2023 TPS629210-Q1

PRODUCTION DATA

8.3.8 Current Limit and Short Circuit Protection

The TPS629210-Q1 is protected against overload and short circuit events. If the inductor current exceeds the current limit, I_{LIM_HS}, the high-side switch is turned off and the low-side switch is turned on to ramp down the inductor current. The high-side FET turns on again only if the current in the low-side FET has decreased below the low-side current limit threshold, I_{LIM_LS}.

Due to internal propagation delay, the actual current can exceed the static current limit during that time. The dynamic current limit is given in Equation 1.

Equation 1.

I_{p e a k (t y p)} = I_{L I M H} + \frac{V_{L}}{L} \times t_{p d}

where:

I_LIMH is the static current limit as specified in the electrical characteristics.
L is the effective inductance at the peak current.
V_L is the voltage across the inductor (V_IN – V_OUT).
t_PD is the internal propagation delay of typically 50 ns.

The current limit can exceed static values, especially if the input voltage is high and very small inductances are used. The dynamic high-side switch peak current can be calculated as follows:

Equation 2.

I_{p e a k (t y p)} = I_{L I M H} + \frac{V_{I N} - V_{O U T}}{L} \times 50 n s

The TPS629210-Q1 also includes a low-side negative current limit (I_LIM:SINK) to protect against excessive negative currents that can occur in forced PMW mode under heavy to light load transient conditions. If the negative current in the low-side switch exceeds the I_LIM:SINK threshold, the low-side switch is disabled. Both the low-side and high-side switches remain off until an internal timer re-enables the high-side switch based on the selected PWM switching frequency.

CAUTION: TI recommends that the inductor be sized such that the inductor ripple current, ΔI_L (see Equation 9), does not exceed 1.6 A to avoid the potential for continuous operation of the negative current limit with no output load (I_O = 0 A).