Datasheet
V =V 1+
O REF
• (
R1
−
R2
)
R1= (
V
O
−
V
REF
-1)• R2
V
O
V
I
OUT
FB
R2
GND
EN
IN
≤
0.9 V
≥ 1.7 V
TPS76901
1µF
3
1
4
2
R1
5
ESR = 0.2 Ω
4.7µF
TPS76901-EP
SLVSA53A –NOVEMBER 2009–REVISED DECEMBER 2009
www.ti.com
Table 1. CAPACITOR SELECTION
PART NO. MANUFACTURER VALUE MAX ESR
(1)
SIZE (H x L x W)
(1)
T494B475K016AS KEMET 4.7 μF 1.5 Ω 1.9 x 3.5 x 2.8
195D106x0016x2T SPRAGUE 10 μF 1.5 Ω 1.3 x 7.0 x 2.7
695D106x003562T SPRAGUE 10 μF 1.3 Ω 2.5 x 7.6 x 2.5
TPSC475K035R0600 AVX 4.7 μF 0.6 Ω 2.6 x 6.0 x 3.2
(1) Size is in mm. ESR is maximum resistance in Ohms at 100 kHz and T
A
= 25°C. Contact manufacturer for minimum ESR values.
OUTPUT VOLTAGE PROGRAMMING
The output voltage of the TPS76901 adjustable regulator is programmed using an external resistor divider as
shown in Figure 6. The output voltage is calculated using:
(1)
Where:
V
REF
= 1.127 V typ (the internal reference voltage)
Resistors R1 and R2 should be chosen for approximately 7-μA divider current. Lower value resistors can be
used but offer no inherent advantage and waste more power. Higher values should be avoided as leakage
currents at FB increase the output voltage error. The recommended design procedure is to choose R2 = 169 kΩ
to set the divider current at 7 μA and then calculate R1 using:
(2)
Note:
1. The above calculations hold good for room temperature values only.
Figure 6. Adjustable LDO Reulator Programming
REGULATOR PROTECTION
The TPS76901 PMOS-pass transistor has a built-in back diode that conducts reverse current when the input
voltage drops below the output voltage (e.g., during power down). Current is conducted from the output to the
input and is not internally limited. If extended reverse voltage operation is anticipated, external limiting might be
appropriate.
The TPS76901 features internal current limiting protection. During normal operation, the TPS76901 limits output
current to approximately 350 mA. When current limiting engages, the output voltage scales back linearly until the
over current condition ends.
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Product Folder Link(s): TPS76901-EP