TS9005

600mA Low Noise CMOS LDO

3/7

Version: A07

Application Information

Input / Output Capacitor

It is recommended to use a 0.47uF capacitor on the TS9005/A input and a 0.47uF capacitor on the output. For high

regulation performance, larger input capacitor values and lower ESRs provide better noise rejection and line-transient

response. The output noise, load-transient response, stability, and power-supply rejection can be improved by using

large output capacitors. Low ESR ceramic capacitors provide optimal performance and save space.

Power Supply Rejection and Transient Response

The PSRR and transient response can be improved by increasing the values of the input and output bypass

capacitors, and through passive filtering techniques

Function Description

Description

The TS9005/A is an ultra-low-noise, low-quiescent current, low-dropout linear regulator. It is supplied in a SOT-25

package for difference applications. This device can supply loads up to 600mA. As shown in the functional block

diagram, the TS9005/A consists of a reference and noise bypass circuit, error amplifier, output drive transistor, internal

feedback voltage divider, thermal sensor, and short circuit current limiter. The internal reference is connected to the

error amplifier’s inverting input. The error amplifier compares this reference with the feedback voltage and amplifies the

difference. If the feedback voltage is lower than the reference voltage, the pass transistor gate is pulled low. This allows

more current to pass to the output and increases the output voltage.

Stability

The TS9005/A is a high performance LDO emphasizing stability with low output capacitance. It is able to maintain

stability with an output capacitor can also be increased to optimize performance. The TS9005/A will remain stable and

in regulation with no load, unlike many other voltage regulators.

Internal P-Channel Pass Transistor

The TS9005/A features a low impedance P-channel MOSFET pass transistor. This provides several advantages over

similar designs using a PNP pass transistor, including low operating power and longer battery life. The TS9005/A

consumes only 100µA of quiescent current under most conditions.

Output Short-Circuit Current Limit

The TS9005/A includes a current limiter, which monitors and controls the pass transistor’s gage voltage, limiting the

output current to about 420mA, for example, in a short-circuit output situation.

Shutdown

The TS9005/A also features a low-power active shutdown mode. It has a switch that turns off the device when disabled.

This allows the output capacitor and load to discharge and de-energize the load. In the shutdown mode, the internal

functional blocks, such as voltage reference and the error amplifier, are turned off completely, and the quiescent current

is less than 1µA.

Thermal Protection Shutdown

The thermal protection shutdown function protects the device from operating in over temperature condition. When the

junction temperature exceeds +160oC, the thermal sensor signals the shutdown logic, turning off the pass transistor

and allowing the IC to tool down. The thermal sensor turns the pass transistor on again after the IC’s junction

temperature drops to +140oC.

Soft-Start Circuitry

The TS9005/A includes a soft-start circuitry to limit inrush current at turn-on. During power up, the output capacitor and

output load are charged with a reduce output current. Shortly after the initial power up, the soft-start feature is

terminated and normal operation is resumed.