50/100mA SOT-23 CMOS RF LDO™ Regulators
INTERNAL V
DD
V
IN
C
NOISE
BANDGAP
REFERENCE
V
REF
ERROR
AMPLIFIER
TRANS-
CONDUCTANCE
AMPLIFIER
V
OUT
FEEDBACK
GND
ON/OFF
Figure 2: ILC7080/81 RF LDO regulator block digram
Shutdown (ON/OFF) Operation
The ILC7080/81 output can be turned off by applying 0.4V
or less to the device’s ON/OFF pin (pin 3). In shutdown
mode, the ILC7080/81 draws less than 1mA quiescent cur-
rent. The output of the ILC7081 is enabled by applying 2V
to 13V at the ON/OFF pin. In applications where the
ILC7080/81 output will always remain enabled, the ON/OFF
pin may be connected to V
IN
(pin 1). The ILC7080/81’s
shutdown circuitry includes hysteresis, as such the device
will operate properly even if a slow moving signal is applied
to the ON/OFF pin. The device’s shutdown pin includes a
2MΩ internal pull down resistor connected to ground.
Short Circuit Protection
The ILC7080/81 output can withstand momentary short cir-
cuit to ground. Moreover, the regulator can deliver very high
output peak current due to its 1A instantaneous short circuit
current capability.
Thermal Protection
The ILC7080/81 also includes a thermal protection circuit
which shuts down the regulator when die temperature
exceeds 170°C due to overheating. In thermal shutdown,
once the die temperature cools to below 160°C, the regula-
tor is enabled. If the die temperature is excessive due to
high package power dissipation, the regulator’s thermal cir-
cuit will continue to pulse the regulator on and off. This is
called thermal cycling.
Excessively high die temperature may occur due to high dif-
ferential voltage across the regulator or high load current or
high ambient temperature or a combination of all three.
Thermal protection protects the regulator from such fault
conditions and is a necessary requirement in today’s
designs. In normal operation, the die temperature should be
limited to under 150°C.
Impala Linear Corporation
ILC7080/81 1.1
Adjustable Output Voltage
Figure 3 shows how an adjustable output voltage can be
easily achieved using ILC7080/81-ADJ. The output voltage,
V
OUT
is given by the following equation:
V
OUT
= 1.24V x (R1/R2 + 1)
R1
V
OUT
5
R2
SOT23-5
4
V
ADJ
C
OUT
V
IN
C
IN
ILC7080-ADJ
ILC7081-ADJ
1
2
3
ON
OFF
Figure 3: Application circuit for adjustable output voltage
For best results, a resistor value of 470kΩ or less may be
used for R2. The output voltage can be programmed from
2.5V to 12V.
Note:
An external capacitor should not be connected to the
adjustable feedback pin (pin 4). Connecting an external capacitor
to pin 4 may cause regulator instability and lead to oscillations.
(408) 574-3939
www.impalalinear.com
Sept. 1998
6
IMPALA [ Impala Linear Corporation ]
