Datasheet LT1121, LT1121-3.3, LT1121-5 (Analog Devices) - 8

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