Datasheet LT1528 (Analog Devices) - 7
| Manufacturer | Analog Devices |
| Description | 3A Low Dropout Regulator for Microprocessor Applications |
| Pages / Page | 12 / 7 — PIN FUNCTIONS SHDN (Pin 4):. VIN (Pin 5):. Figure 1. Kelvin Sense … |
| File Format / Size | PDF / 170 Kb |
| Document Language | English |
PIN FUNCTIONS SHDN (Pin 4):. VIN (Pin 5):. Figure 1. Kelvin Sense Connection. APPLICATIONS INFORMATION. Adjustable Operation
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LT1528
PIN FUNCTIONS SHDN (Pin 4):
This pin is used to put the device into the device is more than six inches away from the main shutdown. In shutdown the output of the device is turned input fi lter capacitor. The LT1528 is designed to withstand off. This pin is active low. The device will be shut down if reverse voltages on the input pin with respect to ground the SHDN pin is actively pulled low. The SHDN pin current and the OUTPUT pin. In the case of reversed input, the with the pin pulled to ground will be 60μA. The SHDN pin LT1528 will act as if there is a diode in series with its input. is internally clamped to 7V and – 0.6V (one VBE). This al- There will be no reverse current fl ow into the LT1528 and lows the SHDN pin to be driven directly by 5V logic or by no reverse voltage will appear at the load. The device will open collector logic with a pull-up resistor. The pull-up protect both itself and the load. resistor is only required to supply the leakage current of the open collector gate, normally several microamperes. R 5 1 P Pull-up current must be limited to a maximum of 5mA. IN OUT A curve of SHDN pin input current as a function of volt- LT1528 age appears in the Typical Performance Characteristics + + 4 2 section. If the SHDN pin is not used it can be left open VIN SHDN SENSE LOAD GND circuit. The device will be active output on if the SHDN 3 pin is not connected. RP 1528 F01
VIN (Pin 5):
Power is supplied to the device through the input pin. The input pin should be bypassed to ground if
Figure 1. Kelvin Sense Connection APPLICATIONS INFORMATION
The LT1528 is a 3A low dropout regulator optimized for into the SENSE pin. The output voltage can be calculated microprocessor applications. Dropout voltage is only 0.6V using the formula in Figure 2. The value of R1 should be at 3A output current. With the SENSE pin shorted to the less than 330Ω to minimize errors in the output voltage OUTPUT pin, the output voltage is set to 3.3V. The device caused by the SENSE pin current. Note that in shutdown operates with a quiescent current of 400μA. In shutdown, the output is turned off and the divider current will be the quiescent current drops to only 125μA. The LT1528 zero. Curves of SENSE Pin Voltage vs Temperature and incorporates several protection features, including protec- SENSE Pin Current vs Temperature appear in the Typical tion against reverse input voltages. If the output is held Performance Characteristics section. at the rated output voltage when the input is pulled to 5 1 ground, the LT1528 acts like it has a diode in series with IN OUT VOUT + its output and prevents reverse current fl ow. V R2 IN LT1528 4 2
Adjustable Operation
SHDN SENSE GND The LT1528 can be used as an adjustable regulator with 3 R1 an output voltage range of 3.3V to 14V. The output voltage is set by the ratio of two external resistors as shown in R2 Figure 2. The device servos the output voltage to maintain VOUT = 3.3V 1 + + (ISENSE)(R2) R1 the voltage at the SENSE pin at 3.3V. The current in R1 VSENSE = 3.3V is then equal to 3.3V/R1. The current in R2 is equal to ISENSE = 130μA AT 25°C 1528 F02 the sum of the current in R1 and the SENSE pin current. OUTPUT RANGE = 3.3V TO 14V The SENSE pin current, 130μA at 25°C, fl ows through R2
Figure 2. Adjustable Operation
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PIN FUNCTIONS SHDN (Pin 4):
This pin is used to put the device into the device is more than six inches away from the main shutdown. In shutdown the output of the device is turned input fi lter capacitor. The LT1528 is designed to withstand off. This pin is active low. The device will be shut down if reverse voltages on the input pin with respect to ground the SHDN pin is actively pulled low. The SHDN pin current and the OUTPUT pin. In the case of reversed input, the with the pin pulled to ground will be 60μA. The SHDN pin LT1528 will act as if there is a diode in series with its input. is internally clamped to 7V and – 0.6V (one VBE). This al- There will be no reverse current fl ow into the LT1528 and lows the SHDN pin to be driven directly by 5V logic or by no reverse voltage will appear at the load. The device will open collector logic with a pull-up resistor. The pull-up protect both itself and the load. resistor is only required to supply the leakage current of the open collector gate, normally several microamperes. R 5 1 P Pull-up current must be limited to a maximum of 5mA. IN OUT A curve of SHDN pin input current as a function of volt- LT1528 age appears in the Typical Performance Characteristics + + 4 2 section. If the SHDN pin is not used it can be left open VIN SHDN SENSE LOAD GND circuit. The device will be active output on if the SHDN 3 pin is not connected. RP 1528 F01
VIN (Pin 5):
Power is supplied to the device through the input pin. The input pin should be bypassed to ground if
Figure 1. Kelvin Sense Connection APPLICATIONS INFORMATION
The LT1528 is a 3A low dropout regulator optimized for into the SENSE pin. The output voltage can be calculated microprocessor applications. Dropout voltage is only 0.6V using the formula in Figure 2. The value of R1 should be at 3A output current. With the SENSE pin shorted to the less than 330Ω to minimize errors in the output voltage OUTPUT pin, the output voltage is set to 3.3V. The device caused by the SENSE pin current. Note that in shutdown operates with a quiescent current of 400μA. In shutdown, the output is turned off and the divider current will be the quiescent current drops to only 125μA. The LT1528 zero. Curves of SENSE Pin Voltage vs Temperature and incorporates several protection features, including protec- SENSE Pin Current vs Temperature appear in the Typical tion against reverse input voltages. If the output is held Performance Characteristics section. at the rated output voltage when the input is pulled to 5 1 ground, the LT1528 acts like it has a diode in series with IN OUT VOUT + its output and prevents reverse current fl ow. V R2 IN LT1528 4 2
Adjustable Operation
SHDN SENSE GND The LT1528 can be used as an adjustable regulator with 3 R1 an output voltage range of 3.3V to 14V. The output voltage is set by the ratio of two external resistors as shown in R2 Figure 2. The device servos the output voltage to maintain VOUT = 3.3V 1 + + (ISENSE)(R2) R1 the voltage at the SENSE pin at 3.3V. The current in R1 VSENSE = 3.3V is then equal to 3.3V/R1. The current in R2 is equal to ISENSE = 130μA AT 25°C 1528 F02 the sum of the current in R1 and the SENSE pin current. OUTPUT RANGE = 3.3V TO 14V The SENSE pin current, 130μA at 25°C, fl ows through R2
Figure 2. Adjustable Operation
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