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LT1239 Datasheet(PDF) 6 Page - Linear Technology |
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LT1239 Datasheet(HTML) 6 Page - Linear Technology |
6 / 12 page 6 LT1239 PIN FUNCTIONS ADJ (Pin 1): Adjust Pin of Regulator 1. The regulator will servo the adjust pin to 3.75V referred to ground. Bias current will be approximately 50nA and will flow into the adjust pin. GND (Pin 2): Ground Pin for Regulator 1. Note that the three ground pins (pins 2, 4, 5) are connected together internally and should all be grounded externally. SHDN1 (Pin 3): Shutdown Pin for Regulator 1. Regulator 1 output will be on if the shutdown pin is either: 1) Left floating (open circuit) or 2) pulled up to the 5V rail. If the shutdown function is not used, the shutdown pin is nor- mally left open circuit. Regulator 1 output will be off if the shutdown pin is pulled to ground. The shutdown pin current with the pin pulled to ground will be in the range of 2 µA flowing out of the pin. The shutdown pin current with the pin pulled up to 5V will be zero. GND (Pin 4): Ground. This ground pin is tied to the substrate of the die, between regulator 1 and the rest of the circuit. It is used as an isolation barrier between regulator 1 and the rest of the circuitry. GND (Pin 5): Ground Pin for Regulator 2. SHDN2 (Pin 6): Shutdown Pin for Regulator 2. Regulator 2 output will be on if the shutdown pin is either: 1) Left floating (open circuit) or 2) pulled up to the 5V rail. If the shutdown function is not used, the shutdown pin is nor- mally left open circuit. Regulator 2 output will be off if the shutdown pin is pulled to ground. The shutdown pin current with the pin pulled to ground will be in the range of 2 µA flowing out of the pin. The shutdown pin current with the pin pulled up to 5V will be zero. E/A (IN) (Pin 7): Noninverting Input of the Error Amplifier. This pin should be tied to the center tap point in the output divider for regulator 1. The bias current for this pin will be in the range of 3nA and it will flow out of the pin. E/A (OUT) (Pin 8): Output of the Error Amplifier. This is normally connected to the center tap of the backup cells. NC (Pin 9): Not Connected. INPUT 2 (Pin 10): Input Pin (VCC) for Regulator 2, the Error Amplifier, and the Low-Battery Detection Circuit. IMON 2 (Pin 11): Current Monitor Pin for Regulator 2. If the current monitor function is not used, this pin should be tied to the output pin of regulator 2. OUT 2 (Pin 12): Output of Regulator 2. It is also the inverting input and output of the comparator. If the main 5V system supply is up and running then the comparator output will pull the output of regulator 2 up to 5V. 5VIN (Pin 13): Noninverting Input of the comparator and the collector of the output driver. The collector of the output driver is normally connected to the main 5V system supply. INPUT 1 (Pin 14): Input Pin (VCC) of Regulator 1. IMON 1 (Pin 15): Current Monitor Pin for Regulator 1. The current flowing out of this pin will be approximately 1/200 of the output current of regulator 1. If the current monitor function is not used, this pin should be tied to the output pin of regulator 1. OUT 1 (Pin 16): Output of Regulator 1. Regulator 1: Regulator 1 is used to supply the charging current to the backup batteries. It converts the voltage on the main battery to a fixed output voltage to charge the backup cells. The output voltage is set with a voltage divider connected between the output and ground with a tap point of the divider connected to the adjust pin. The regulator servos its output in order to maintain the adjust pin at 3.75V referred to ground. The resistor divider should be chosen such that the divider current is approxi- mately 5 µA.Thismeanstheimpedancefromtheadjustpin to ground should be approximately 750k Ω. For safety requirements a resistor can be placed between the output pin and the top of the divider that sets the regulated output voltage. The regulator will regulate the voltage at the top of the divider. Quiescent current will be 10 µAto15µA.Output short-circuit current will be approximately 70mA. FUNCTIONAL DESCRIPTIO |
Similar Part No. - LT1239_02 |
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Similar Description - LT1239_02 |
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