Figure 8-1. Switching Frequency versus Output Current (VIN = 5V, VOUT = 1.8V)

8.4.3 100% Duty-Cycle Operation

The device offers a low input-to-output voltage differential by entering 100% duty cycle mode. When the

minimum off-time of typically 30 ns is reached, the TPSM8281x skips switching cycles while it approaches

100% mode. In 100% mode, the high-side MOSFET switch is constantly turned on. This is particularly useful

in battery-powered applications to achieve longest operation time by taking full advantage of the whole battery

voltage range. The minimum input voltage to maintain a minimum output voltage is given by:

VIN (min) = VOUT (min) + IOUT × RDP

(6)

where

• RDP is the resistance from VIN to VOUT, which includes the high-side MOSFET on-resistance and DC

resistance of the inductor

• VOUT (min) is the minimum output voltage the load can accept

8.4.4 Current Limit and Short Circuit Protection

The TPSM8281x is protected against overload and short circuit events. If the inductor current exceeds the

current limit ILIMH, the high-side MOSFET is turned off and the low-side MOSFET is turned on to ramp down

the inductor current. The high-side MOSFET turns on again only if the current in the low-side MOSFET has

decreased below the low-side current limit. Due to internal propagation delays, the actual current can exceed the

static current limit. The dynamic current limit is given as:

(

)

L

peak typ

LIMH

PD

V

I

I

t

L

=

+

×

(7)

where

• ILIMH is the static current limit, as specified in the electrical characteristics

• L is the effective inductance (typically 470nH)

• VL is the voltage across the inductor (VIN - VOUT)

• tPD is the internal propagation delay of typically 50ns

The dynamic peak current is calculated as follows:

(

)

50

IN

OUT

peak typ

LIMH

V

V

I

I

ns

L

-

=

+

×

(8)

The low-side MOSFET also contains a negative current limit to prevent excessive current from flowing back

through the inductor to the input. If the low-side sinking current limit is exceeded, the low-side MOSFET is turned

www.ti.com

TPSM82810, TPSM82813

SLUSDN6B – SEPTEMBER 2019 – REVISED JULY 2024

Copyright © 2024 Texas Instruments Incorporated

Submit Document Feedback

13

Product Folder Links: TPSM82810 TPSM82813