Datasheet

 
 
SLVS333 − AUGUST 2001
15
www.ti.com
TYPICAL CHARACTERISTICS
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
−40 −25 −10 5 20 35 50 65
UVLO − Undervoltage Lockout − V
UNDERVOLTAGE LOCKOUT
vs
JUNCTION TEMPERATURE
T
J
− Junction Temperature − °C
Rising
Falling
80 95 110
Figure 17
APPLICATION INFORMATION
external capacitor requirements on power lines
Ceramic bypass capacitors (0.01-µ to 0.1-µ) between VIN/SWIN1 and GND and SWIN2 and GND, close to the
device, are recommended to improve load transient response and noise rejection.
Bulk capacitors ( 4.7-µF) between VIN/SWIN1 and GND and between SWIN2 and GND are also recommended,
especially if load transients in the hundreds of milliamps with fast rise times are anticipated.
A 66-µF bulk capacitor is recommended from OUTx to ground, especially when the output load is heavy. This
precaution helps reduce transients seen on the power rails. Additionally, bypassing the outputs with a 0.1-µF
ceramic capacitor improves the immunity of the device to short-circuit transients.
LDO output capacitor requirements
Stabilizing the internal control loop requires an output capacitor connected between LDO_OUT and GND. The
minimum recommended capacitance is a 4.7 µF with an ESR value between 200 mΩ and 10 Ω. Solid tantalum
electrolytic, aluminum electrolytic and multilayer ceramic capacitors are all suitable, provided they meet the
ESR requirements.
The adjustable LDO (for voltages lower than 3 V) requires a bypass capacitor across the feedback resistor as
shown in Figure 18. The value of this capacitor is determined by using the following equation:
C
f
+
1
(
63.7e
3
2 3.14 R1
)
* 4pf
where R1 is derived by programming the adjustable LDO (see programming the adjustable LDO regulator
section shown below).
(1)