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TPS62097-Q1

SLVSDZ7 – AUGUST 2017

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Copyright © 2017, Texas Instruments Incorporated

7.3 Feature Description

7.3.1 100% Duty Cycle Mode

The device offers a low input to output voltage dropout by entering 100% duty cycle mode, when the input

voltage reaches the level of the output voltage. In this mode the high-side MOSFET switch is constantly turned

on and the low-side MOSFET is switched off. The minimum input voltage to maintain output regulation,

depending on the load current and output voltage, is calculated as:

where

•

•

•

•

(1)

When the device operates close to 100% duty cycle mode, the TPS62097-Q1 can't enter Power Save Mode

regardless of the load current if the input voltage decreases to typically 15% above the output voltage. The

device maintains output regulation in PWM mode.

7.3.2 Switch Current Limit and Hiccup Short Circuit Protection

The switch current limit prevents the devices from high inductor current and from drawing excessive current from

the battery or input voltage rail. Excessive current might occur with a shorted/saturated inductor or a heavy

turned off and the low-side MOSFET is turned on to ramp down the inductor current. Once this switch current

limit is triggered 32 times, the devices stop switching and enable the output discharge. The devices then

automatically start a new startup after a typical delay time of 100µs has passed. This is HICCUP short circuit

protection and is implemented to reduce the current drawn during a short circuit condition. The devices repeat

this mode until the high load condition disappears.

When the device is in forced PWM mode, the negative current limit of the low-side MOSFET is active. The

negative current limit prevents excessive current from flowing back through the inductor to the input.

7.3.3 Under Voltage Lockout (UVLO)

To avoid mis-operation of the device at low input voltages, an under voltage lockout is implemented, which shuts

7.3.4 Thermal Shutdown

the device temperature falls below the threshold by 20°C, the device returns to normal operation automatically.

7.4 Device Function Modes

7.4.1 Enable and Disable (EN)

The device is enabled by setting the EN pin to a logic High. Accordingly, shutdown mode is forced if the EN pin

is pulled Low with a shutdown current of typically 0.7 μA.

In shutdown mode, the internal power switches as well as the entire control circuitry are turned off. An internal

resistor of 165 Ω discharges the output via the VOS pin smoothly. The output discharge function also works

when thermal shutdown, undervoltage lockout or HICCUP short circuit protection are triggered.

An internal pull-down resistor of 375 kΩ is connected to the EN pin when the EN pin is Low. The pull-down

resistor is disconnected when the EN pin is High.

7.4.2 Power Save Mode and Forced PWM Mode (MODE)

The MODE pin is a multi-functional pin that allows the device operation in forced PWM mode or PWM/PSM

mode, and to select the PWM switching frequency.