LP38859_15 Datasheet, PDF (13/25 Pages) Texas Instruments – 3A Fast-Response High-Accuracy LDO Linear Regulator With Soft Start

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8 Application and Implementation
LP38859
SNVS337F – JUNE 2006 – REVISED SEPTEMBER 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LP38859 can provide 3-A output current with 240-mV dropout voltage (typical). The bias voltage must be in
the range of 3 V to 5.5 V to ensure proper operation of the device. The input voltage must be at least V_OUT +
V_DO, and no higher than whatever value is used for V_BIAS. Minimal input and output capacitors are each 10 μF.
The capacitor on the BIAS pin must be at least 1 μF.
8.2 Typical Application
V_IN
V_BIAS
GND
C_IN
10 2F Ceramic
C_BIAS
1 2F
LP38859-x.x
IN
OUT
BIAS
SS
GND
C_SS
V_OUT
C_OUT
10 2F
Ceramic
GND
Figure 20. LP38859 Typical Application
8.2.1 Design Requirements
For typical high-accuracy LDO linear regulator applications, use the parameters listed in Table 1.
DESIGN PARAMETER
Bias voltage
Input voltage
Output voltages
Output current
Bias capacitor
Input capacitor
Output capacitor
Table 1. Design Parameters
EXAMPLE VALUE
3 V to 5.5 V
1.1 V to 5.5 V
0.8 V, 1.2 V
3 A (maximum)
1 μF (minimum)
10 μF (minimum)
10 uF (minimum)
8.2.2 Detailed Design Procedure
8.2.2.1 External Capacitors
To assure regulator stability, input and output capacitors are required as shown in the Figure 20.
8.2.2.1.1 Output Capacitor
A minimum output capacitance of 10 µF, ceramic, is required for stability. The amount of output capacitance can
be increased without limit. The output capacitor must be located less than 1 cm from the OUT pin of the device
and returned to the device GND pin with a clean analog ground.
Only high quality ceramic types such as X5R or X7R must be used, as the Z5U and Y5F types do not provide
sufficient capacitance over temperature.
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