Datasheet LTC4000-1 (Analog Devices) - 8

LTC4000-1
pin FuncTions (QFN/SSOP) VM (Pin 1/Pin 25):
Voltage Monitor Input. High impedance
ENC (Pin 5/Pin 1):
Enable Charging Pin. High impedance input to an accurate comparator with a 1.193V threshold digital input pin. Pull this pin above 1.5V to enable charg- (typical). This pin controls the state of the RST output ing and below 0.5V to disable charging. Leaving this pin pin. Connect a resistor divider (RVM1, RVM2) between the open causes the internal 2µA pull-up current to pull the monitored voltage and GND, with the center tap point con- pin to 2.5V (typical). nected to this pin. The falling threshold of the monitored
IBMON (Pin 6/Pin 2):
Battery Charge Current Monitor. The voltage is calculated as follows: voltage on this pin is 20 times (typical) the sense voltage (V V • 1.193V CSP,CSN) across the battery current sense resistor (RCS), VM _RST = RVM1 + RVM2 therefore providing a voltage proportional to the battery RVM2 charge current. Connect an appropriate capacitor to this where RVM2 is the bottom resistor between the VM pin pin to obtain a voltage representation of the time-average and GND. Tie to the BIAS pin if voltage monitoring func- battery charge current. Short this pin to GND to disable tion is not used. charge current limit feature.
RST (Pin 2/Pin 26):
High Voltage Open Drain Reset Output.
CX (Pin 7/Pin 3):
Charge Current Termination Pro- When the voltage at the VM pin is below 1.193V, this status gramming. Connect the charge current termination pro- pin is pulled low. When driven low, this pin can disable gramming resistor (R a DC/DC converter when connected to the converter’s CX) to this pin. This pin is a high impedance input to a comparator and sources 5μA of enable pin. This pin can also drive an LED to provide a current. When the voltage on this pin is greater than the visual status indicator of a monitored voltage. Short this charge current monitor voltage (V pin to GND when not used. IBMON), the CHRG pin turns high impedance indicating that the CX threshold is
IIMON (Pin 3/Pin 27):
Input Current Monitor. The voltage reached. When this occurs, the charge current is imme- on this pin is 20 times (typical) the sense voltage (VIN,CLN) diately terminated if the TMR pin is shorted to the BIAS across the input current sense resistor(RIS), therefore pin, otherwise charging continues until the charge termi- providing a voltage proportional to the input current. nation timer expires. The charge current termination value Connect an appropriate capacitor to this pin to obtain a is determined using the following formula: voltage representation of the time-average input current. Leave this pin open when input current monitoring func- 0.25µA • R ( )−0.5mV I CX tion is not needed. C/X = RCS
IFB (Pin 4/Pin 28):
Input Voltage Feedback Pin. This pin is a high impedance input pin used to sense the input voltage Where RCS is the sense resistor connected to the CSP level. In regulation, the input voltage loop sets the voltage and the CSN pins. Note that if RCX = RCL ≤ 19.1kΩ, where on this feedback pin to 1.000V. When the input feedback RCL is the charge current programming resistor, then the voltage drops below 1.000V, the ITH pin is pulled down charge current termination value is one tenth the full charge to reduce the load on the input source. Connect this pin current, more familiarly known as C/10. Short this pin to to the center node of a resistor divider between the IN GND to disable CX termination. pin and GND to set the input voltage regulation level. This
CL (Pin 8/Pin 4):
Charge Current Limit Programming. Con- regulation level can then be obtained as follows: nect the charge current programming resistor (RCL) to this pin. This pin sources 50µA of current. The regulation loop  R  V OFB1 compares the voltage on this pin with the charge current IN _REG = + 1  ROFB2  • 1.000V monitor voltage (VIBMON), and drives the ITH pin accord- ingly to ensure that the programmed charge current limit If the input voltage regulation feature is not used, connect the IFB pin to the BIAS pin. 40001fa 8 For more information www.linear.com/LTC4001-1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Typical Application Related Parts