Datasheet

TPS70445, TPS70448

TPS70451, TPS70458

TPS70402

SLVS307F –SEPTEMBER 2000–REVISED APRIL 2010

www.ti.com

APPLICATION INFORMATION

Input Capacitor

For a typical application, a ceramic input bypass capacitor (0.22 mF to 1 mF) is recommended. This capacitor

should be as close to the input pins as possible. Due to the impedance of the input supply, large transient

currents cause the input voltage to droop. If this droop causes the input voltage to drop below the UVLO

threshold, the device turns off. Therefore, it is recommended to place a larger capacitor in parallel with the

ceramic bypass capacitor at the regulator input. The size of this capacitor depends on the output current, the

response time of the main power supply, and the main power supply distance to the regulator. At a minimum, the

capacitor should be sized to ensure that the input voltage does not drop below the minimum UVLO threshold

voltage during normal operating conditions.

Output Capacitor

As with most LDO regulators, the TPS704xx requires an output capacitor connected between OUT and GND to

stabilize the internal control loop. The minimum recommended capacitance value for V

OUT1

is 22 mF and the ESR

(equivalent series resistance) must be between 50 mΩ and 800 mΩ. The minimum recommended capacitance

value for V

OUT2

is 47 mF and the ESR must be between 50 mΩ and 2 Ω. Solid tantalum electrolytic, aluminum

electrolytic, and multilayer ceramic capacitors are all suitable, provided they meet the requirements described

above. Larger capacitors provide a wider range of stability and better load transient response. Table 1 gives a

partial listing of surface-mount capacitors suitable for use with the TPS704xx for fast transient response

applications.

This information, along with the ESR graphs, is included to assist in selection of suitable capacitance for user

applications. When necessary to achieve low height requirements along with high output current and/or high load

capacitance, several higher ESR capacitors can be used in parallel to meet the guidelines above.

Table 1. Partial Listing of TPS704xx-Compatible Surface-Mount Capacitors

VALUE MANUFACTURER MFR PART NO.

680 mF Kemet T510X6871004AS

470 mF Sanyo 4TPB470M

150 mF Sanyo 4TPC150M

220 mF Sanyo 2R5TPC220M

100 mF Sanyo 2R5TPC220M

68 mF Sanyo 10TPC68M

68 mF Kemet T495D6861006AS

47 mF Kemet T495D4761010AS

33 mF Kemet T495C3361016AS

22 mF Kemet T495C2261010AS