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Programming the TPS75x01Q Adjustable LDO Regulator
V =V ´
OUT ref
(1+)
R
R
1
2
(1)
R =( 1) R-
1 2
´
V
V
OUT
ref
(2)
IN
EN
GND
FB/SENSE
OUT
PG/
RESET
PGor OutputRESET
V
OUT
V
IN
0.22 Fm
250kW
TPS75x01Q
C
OUT
R
1
R
2
> 2.0V
< 0.7V
OUTPUTVOLTAGE
PROGRAMMINGGUIDE
R
1
R
2
UNIT
OUTPUT
VOLTAGE
2.5V
3.3V
3.6V
33.2
53.6
61.9
30.1
30.1
30.1
kW
kW
kW
NOTE:Toreducenoiseandpreventoscillation,
R andR mustbeascloseaspossibletothe
FB/SENSEterminal.
1 2
Regulator Protection
TPS751xxQ
TPS753xxQ
SLVS241C – MARCH 2000 – REVISED OCTOBER 2007
The output voltage of the TPS77x01Q adjustable regulator is programmed using an external resistor divider as
shown in Figure 25 . The output voltage is calculated using Equation 1 :
Where:
• V
ref
= 1.1834 V typ (the internal reference voltage)
Resistors R
1
and R
2
should be chosen for approximately 40 μ A 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 R
2
= 30.1 k Ω
to set the divider current at approximately 40 μ A and then calculate R
1
using Equation 2 :
Figure 25. TPS75x01Q Adjustable LDO Regulator Programming
The TPS751xxQ and TPS753xxQ PMOS-pass transistors have a built-in back diode that conducts reverse
currents when the input voltage drops below the output voltage (for example, during power down). Current is
conducted from the output to the input and is not internally limited. When extended reverse voltage is anticipated,
external limiting may be appropriate.
The TPS751xxQ and TPS753xxQ also feature internal current limiting and thermal protection. During normal
operation, the TPS751xxQ and TPS753xxQ limit output current to approximately 3.3 A. When current limiting
engages, the output voltage scales back linearly until the overcurrent condition ends. While current limiting is
designed to prevent gross device failure, care should be taken not to exceed the power dissipation ratings of the
package. If the temperature of the device exceeds +150 ° C (typ), thermal-protection circuitry shuts it down. Once
the device has cooled below +130 ° C (typ), regulator operation resumes.
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