LP38853_15 Datasheet, PDF (14/30 Pages) Texas Instruments – LP38853 3A Fast-Response High-Accuracy Adjustable LDO Linear Regulator with Enable and Soft-Start

LP38853
SNVS335E – DECEMBER 2006 – REVISED NOVEMBER 2015
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V_OUT
0.8 V
0.9 V
1V
1.1 V
1.2 V
1.3 V
1.4 V
1.5 V
1.6 V
1.7 V
1.8 V
Table 1. Suggested Resistor Values
R1
1.07 kΩ
1.50 kΩ
1.00 kΩ
1.65 kΩ
1.40 kΩ
1.15 kΩ
1.07 kΩ
2.00 kΩ
1.65 kΩ
2.55 kΩ
2.94 kΩ
R2
1.78 kΩ
1.87 kΩ
1.00 kΩ
1.37 kΩ
1.00 kΩ
715 Ω
590 Ω
1.00 kΩ
750 Ω
1.07 kΩ
1.13 kΩ
C_FF
12 nF
8.2 nF
12 nF
8.2 nF
10 nF
12 nF
12 nF
6.8 nF
8.2 nF
5.6 nF
4.7 nF
F_Z
12.4 kHz
12.9 kHz
13.3 kHz
11.8 kHz
11.4 kHz
11.5 kHz
12.4 kHz
11.7 kHz
11.8 kHz
11.1 kHz
11.5 kHz
Refer to the TI Application Note AN-1378 Method for Calculating Output Voltage Tolerances in Adjustable
Regulators (SNVA112) for additional information on how resistor tolerances affect the calculated V_OUT value.
7.3.6 Enable (EN) Operation
The EN pin provides a mechanism to enable, or disable, the regulator output stage. The EN pin has an internal
pullup, through a typical 180-kΩ resistor, to V_BIAS. The EN pin can be left open or connected V_BIAS if the enable
function is not needed.
7.4 Device Functional Modes
7.4.1 Input Voltage
The input voltage (V_IN) is the high-current external voltage rail that is regulated down to a lower voltage, which is
applied to the load. The input voltage must be at least V_OUT + V_DO, and no higher than whatever value is used for
V_BIAS.
For applications where V_BIAS is higher than 4.5 V, V_IN must be no greater than 4.5 V, otherwise output voltage
accuracy may be affected.
7.4.2 Bias Voltage
The bias voltage (V_BIAS) is a low-current external voltage rail required to bias the control circuitry and provide
gate drive for the N-FET pass transistor. When V_OUT is set to 1.2 V, or less, V_BIAS may be anywhere in the
operating range of 3 V to 5.5 V. If V_OUT is set higher than 1.2 V, V_BIAS must be between 4.5 V and 5.5 V to
ensure proper operation of the device.
7.4.3 Enable Operation
If the EN pin is actively driven, pulling the EN pin above the V_EN threshold of 1.25 V (typical) turns on the
regulator output; pulling the EN pin below the V_EN threshold turns off the regulator output. There is approximately
100 mV of hysteresis built into the enable threshold provide noise immunity.
If the enable function is not needed the EN pin must be left open, or connected directly to V_BIAS. If the EN pin is
left open, stray capacitance on this pin must be minimized; otherwise, the output turnon is delayed while the
stray capacitance is charged through the internal resistance (r_EN).
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