ADJ

GND

TPS7B4250-Q1

TPS7A6650-Q1

GND

10 µF

22 µF

CT

PG

EN

10 µF

2.2 µF

Sensor

ADC

MCU I/O

TPS7B4250-Q1

www.ti.com

SLVSCA0A – OCTOBER 2013 – REVISED NOVEMBER 2013

Tracking Regulator with ENABLE Circuit

By pulling the reference voltage of the device below 0.8 V, the IC disables and enters a sleep state where the

device draws 7.5 µA (typical) from the power supply. In a real application, the reference voltage is generally

sourced from another LDO voltage rail. A case where the device must be disabled without a shutdown of the

reference voltage can occur. In such case, the device can be configured as shown in Figure 18. The

TPS7A6650-Q1 device is a 150-mA LDO with ultra-low quiescent current that is used as a reference voltage to

the TPS7B4250-Q1 device and also as a power supply to the ADC. In a configuration as shown in Figure 18, the

status of the device is controlled by an MCU I/O.

Figure 18. Tracking LDO With Enable Circuit

External Capacitors

terminals.

The output capacitor for the TPS7B4250-Q1 device is required for stability. Without the output capacitor, the

regulator oscillates. The actual size and type of the output capacitor can vary based on the application load and

temperature range. The effective series resistance (ESR) of the capacitor is also a factor in the IC stability. The

worst case is determined at the minimum ambient temperature and maximum load expected. To ensure stability

of TPS7B4250-Q1 device, the device requires an output capacitor between 1 µF and 50 µF with an ESR range

between 0.001

Ω and 20 Ω that can cover most types of capacitor ESR variation under the recommend operating

conditions. As a result, the output capacitor selection is flexible.

The capacitor must also be rated at all ambient temperature expected in the system. To maintain regulator

stability down to –40°C, use a capacitor rated at that temperature.

Copyright © 2013, Texas Instruments Incorporated

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