LT1627 LINER [Linear Technology], LT1627 Datasheet - Page 8

• Manufacturer Part Number: LT1627
• Description: Micropower Low Dropout Regulators with Shutdown
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
LT1121/LT1121-3.3/LT1121-5
TYPICAL PERFORMANCE CHARACTERISTICS
Input Pin: Power is supplied to the device through the
input pin. The input pin should be bypassed to ground if
the device is more than six inches away from the main
input filter capacitor. In general the output impedance of
a battery rises with frequency so it is usually adviseable to
include a bypass capacitor in battery-powered circuits. A
bypass capacitor in the range of 0.1µF to 1µF is sufficient.
The LT1121 is designed to withstand reverse voltages on
the input pin with respect to both ground and the output
pin. In the case of a reversed input, which can happen if
a battery is plugged in backwards, the LT1121 will act as
if there is a diode in series with its input. There will be
no reverse current flow into the LT1121 and no reverse
voltage will appear at the load. The device will protect both
itself and the load.
Output Pin: The output pin supplies power to the load. An
output capacitor is required to prevent oscillations. See
the Applications Information section for recommended
value of output capacitance and information on reverse
output characteristics.
Shutdown Pin: This pin is used to put the device into
shutdown. In shutdown the output of the device is turned
8
–10
–15
–20
–25
–30
–35
–40
–5
0
–50
Load Regulation
ΔI
* ADJ PIN TIED TO
LOAD
OUTPUT PIN
–25
= 1mA TO 150mA
0
TEMPERATURE (°C)
LT1121*
25
50
75
LT1121-3.3
LT1121-5
100
1121 G28
125
–0.1
–0.2
150
100
0.2
0.1
0
0
LT1121-5
Load Transient Response
V
C
C
IN
IN
OUT
0.1
= 6V
= 0.1μF
= 1μF
0.2 0.3
0.4
TIME (ms)
0.5
off. This pin is active low. The device will be shut down if
the shutdown pin is pulled low. The shutdown pin current
with the pin pulled to ground will be 6µA. The shutdown
pin is internally clamped to 7V and – 0.6V (one V
allows the shutdown pin to be driven directly by 5V logic or
by open collector logic with a pull-up resistor. The pull-up
resistor is only required to supply the leakage current of
the open collector gate, normally several microamperes.
Pull-up current must be limited to a maximum of 20mA.
A curve of shutdown pin input current as a function of
voltage appears in the Typical Performance Characteristics.
If the shutdown pin is not used it can be left open circuit.
The device will be active, output on, if the shutdown pin
is not connected.
Adjust Pin: For the adjustable LT1121, the adjust pin
is the input to the error amplifier. This pin is internally
clamped to 6V and –0.6V (one V
of 150nA which flows into the pin. See Bias Current curve
in the Typical Performance Characteristics. The adjust
pin reference voltage is 3.75V referenced to ground. The
output voltage range that can be produced by this device
is 3.75V to 30V.
0.6
0.7
0.8
0.9
1121 G29
1.0
–0.1
–0.2
150
100
0.2
0.1
50
0
0
LT1121-5
Load Transient Response
V
C
C
IN
IN
OUT
0.1
= 6V
= 0.1μF
= 3.3μF
0.2 0.3
BE
). It has a bias current
0.4
TIME (ms)
0.5
0.6
0.7
0.8
BE
). This
0.9
1121 G30
1121fg
1.0