Datasheet
TPS72201, TPS72215
TPS72216, TPS72218
SLVS390B – DECEMBER 2001 – REVISED MAY 2002
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9
PROGRAMMING THE TPS72201 ADJUSTABLE LDO REGULATOR
The output voltage of the TPS72201 adjustable regulator is programmed using an external resistor divider as shown in
Figure 18. The output voltage is calculated using:
V
O
+ V
ref
ǒ
1 )
R1
R2
Ǔ
(1
)
Where:
V
ref
= 1.225 V typ (the internal reference voltage)
Resistors R1 and R2 should be chosen for approximately 10-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 = 121 kΩ to set the divider current at 10 µA and then calculate R1 using:
R1 +
ǒ
V
O
V
ref
* 1
Ǔ
R2
(2)
Where:
V
ref
= 1.225
V
O
V
I
OUT
FB
R2
GND
EN
IN
≤0.9 V
≥1.7 V
TPS72201
†
1% values shown.
3
1
4
2
R1
5
0.1 µF
OUTPUT
VOLTAGE
(V)
R1 R2
2.5
3.3
127
205
121
121
OUTPUT VOLTAGE
PROGRAMMING GUIDE
DIVIDER RESISTANCE
(kΩ)
†
0.1 µF
Figure 18. TPS72201 Adjustable LDO Regulator Programming
REGULATOR PROTECTION
The TPS722xx pass element has a built-in back diode that safely 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 is anticipated, external limiting might be appropriate.
The TPS722xx also features internal current limiting and thermal protection. During normal operation, the TPS722xx limits
output current to approximately 350 mA. 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 170°C, thermal-protection
circuitry shuts it down. Once the device has cooled down to below 150°C, regulator operation resumes.