Datasheet LTC4008 (Analog Devices) - 7

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PIN FUNCTIONS DCIN (Pin 1):
External DC Power Source Input. Bypass this resistor. The voltage at this pin provides a linear indica- pin with at least 0.01µF. See “Applications Information” tion of charging current. Peak current is equivalent to section. 1.19V. Zero current is approximately 0.309V. A capaci-
I
tor from PROG to ground is required to filter higher fre-
CL (Pin 2):
Input Current Limit Indicator. Active low dig- ital output. Internal 10µA pul -up to 3.5V. Pul ed low if quency components. The maximum program resistance the charger current is being reduced by the input current to ground is 100k. Values higher than 100k can cause the limiting function. The pin is capable of sinking at least charger to shut down. 100µA. If VLOGIC > 3.3V, add an external pull-up.
CSP (Pin 11):
Current Amplifier CA1 Input. The CSP and
ACP/SHDN (Pin 3):
Open-drain output used to indicate if BAT pins measure the voltage across the sense resis- the AC adapter voltage is adequate for charging. Active high tor, RSENSE, to provide the instantaneous current signals digital output. Internal 10µA pull-up to 3.5V. The charger required for both peak and average current mode operation. can also be shutdown by pulling this pin below 1V. The pin
BAT (Pin 12):
Battery Sense Input and the Negative is capable of sinking at least 100µA. If VLOGIC > 3.3V, add Reference for the Current Sense Resistor. an external pull-up. (LTC4008-1: ACP function disabled.)
BATMON (Pin 13):
Output Voltage Representing Battery
RT (Pin 4):
Thermistor Clocking Resistor. Use a 150k resis- Voltage. Switched off to reduce standby current drain tor as a nominal value. This resistor is always required. when AC is not present. An external voltage divider If this resistor is not present, the charger will not start. from BATMON to VFB sets the charger float voltage.
FAULT (Pin 5):
Active low open-drain output that indi- Recommended minimum load resistance is 100k. cates that charger operation has suspended due to the
FLAG (Pin 14):
Active low open-drain output that indi- thermistor exceeding allowed values. A pull-up resistor cates when charging current has declined to 10% of max is required if this function is used. The pin is capable of programmed current. A pull-up resistor is required if this sinking at least 100µA. function is used. The pin is capable of sinking at least
GND (Pin 6):
Ground for Low Power Circuitry. 100µA. This function is latching. To clear it, user must cycle the ACP/SHDN pin.
VFB (Pin 7):
Input of Voltage Feedback Error Amplifier, EA, in the “Block Diagram”.
CLN (Pin 15):
Negative Input to the Input Current Limiting Amplifier CL1. The threshold is set at 100mV below the
NTC (Pin 8):
A thermistor network is connected from NTC voltage at the CLP pin. When used to limit input current, to GND. This pin determines if the battery temperature is a filter is needed to filter out the switching noise. If no safe for charging. The charger and timer are suspended current limit function is desired, connect this pin to CLP. and the FAULT pin is driven low if the thermistor indicates a temperature that is unsafe for charging. The thermistor
CLP (Pin 16):
This pin serves as a positive reference for function may be disabled with a 300k to 500k resistor the input current limit amplifier, CL1. It also serves as the from DCIN to NTC. power supply for the IC.
I TGATE (Pin 17):
Drives the top external PMOSFET of the
TH (Pin 9):
Control Signal of the Inner Loop of the Current Mode PWM. Higher I battery charger buck converter. TH voltage corresponds to higher charging current in normal operation. A 6k resistor in
PGND (Pin 18):
High Current Ground Return for BGATE series with a capacitor of at least 0.1µF to GND provides Driver. loop compensation. Typical full-scale output current is
BGATE (Pin 19):
Drives the bottom external N-MOSFET 40µA. Nominal voltage range for this pin is 0V to 3V. of the battery charger buck converter.
PROG (Pin 10):
Current Programming/Monitoring Input/
INFET (Pin 20):
Drives the gate of the external input Output. An external resistor to GND programs the peak P-MOSFET. (LTC4008-1: No Connection) charging current in conjunction with the current sensing Rev C For more information www.analog.com 7 Document Outline Description Typical Application Absolute Maximum Ratings Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Test Circuit Operation Applications Information Package Description Revision History Related Parts