LP38798 Datasheet, PDF (13/23 Pages) Texas Instruments – LP38798-ADJ High PSRR, Ultra Low Noise, 800 mA Linear Voltage Regulator for RF/Analog Circuits

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Functional Block Diagram
LP38798
SNOSCT6A – MARCH 2013 – REVISED MAY 2013
APPLICATIONS INFORMATION
IN
LP38798SD-ADJ
OUT
IN
IN(CP)
CP
EN
Active Ripple
Rejection
200 mV
PMOS
Current
Limit
UVLO
Thermal
Shutdown
Charge Pump
3.5 MHz
tau= 2s
I_EN
2 PA
I_SET
52 PA
5V
1.24V
V_REF
1.200V
OUT
OUT(FB)
98%
SET
99.5%
FB
GND(CP)
GND
Package Information
The LP38798-ADJ is available in the 12-Lead WSON surface mount package that allows for increased power
dissipation compared to the standard PSOP-8 and WQFN-8 packages.
External Capacitors
Like any low-dropout regulator, the LP38798-ADJ requires external capacitors for regulator stability. These
capacitors must be correctly selected for optimum performance.
INPUT CAPACITOR: The minimum recommended input capacitance is 1 µF, ceramic or tantalum. However, if
the LP38798 is operating in conditions where input ripple, fast changes in the input voltage, or large changes in
the load current demand are expected, a minimum input capacitance of 10 µF is strongly recommended.
Ceramic capacitor tolerance and variations due temperature and applied voltage must be considered when
selecting a capacitor to assure the minimum input capacitance requirement is met over the intended operating
range.
The input capacitor must be located as close as physically possible to the input pin and returned to a clean
analog ground. Any good quality tantalum capacitor may be used, while a ceramic capacitor should be X5R or
X7R rated with appropriate adjustments due to the loss of capacitance value from the applied DC voltage.
Larger input capacitance values are encouraged if fast output current steps are expected, as this will minimize
voltage drops at the input pin. However, if there is any PCB trace inductance between the bulk supply and the
input pin it is recommended that a tantalum capacitor be placed in parallel with the ceramic input capacitor. This
will help to damp out undesired ringing that may occur during input transient conditions.
Copyright © 2013, Texas Instruments Incorporated
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