Datasheet LTC4006 (Analog Devices) - 6

LTC4006
U U U PI FU CTIO S R CSP (Pin 9):
Current Amplifier CA1 Input. This pin and the
T (Pin 4):
Timer Resistor. The timer period is set by placing a resistor, R BAT pin measure the voltage across the sense resistor, RT, to GND. RSENSE, to provide the instantaneous current signals re- The timer period is tTIMER = (1hour • RRT/154k) quired for both peak and average current mode operation. If this resistor is not present, the charger will not start.
BAT (Pin 10):
Battery Sense Input and the Negative
GND (Pin 5):
Ground for low power circuitry. Reference for the Current Sense Resistor. A precision
NTC (Pin 6):
A thermistor network is connected from NTC internal resistor divider sets the final float potential on this to GND. This pin determines if the battery temperature is pin. The resistor divider is disconnected during shutdown. safe for charging. The charger and timer are suspended if
CLP (Pin 11):
Positive Input to the Supply Current Limiting the thermistor indicates a temperature that is unsafe for Amplifier, CL1. The threshold is set at 100mV above the charging. The thermistor function may be disabled with a voltage at the CLN pin. When used to limit supply current, 300k to 500k resistor from DCIN to NTC. a filter is needed to filter out the switching noise. If no
I
current limit function is desired, connect this pin to CLN.
TH (Pin 7):
Control Signal of the Inner Loop of the Current Mode PWM. Higher ITH voltage corresponds to higher
CLN (Pin 12):
Negative Reference for the Input Current charging currrent in normal operation. A 6.04k resistor, in Limit Amplifier, CL1. This pin also serves as the power series with a capacitor of at least 0.1µF to GND, provides supply for the IC. A 10µF to 22µF bypass capacitor should loop compensation. Typical full-scale output current is be connected as close as possible to this pin. 40µA. Nominal voltage range for this pin is 0V to 3V.
TGATE (Pin 13):
Drives the top external P-channel MOSFET
IMON (Pin 8):
Current Monitoring Output. The voltage at of the battery charger buck converter. this pin provides a linear indication of charging current.
PGND (Pin 14):
High Current Ground Return for the BGATE Peak current is equivalent to 1.19V. Zero current is ap- Driver. proximately 0.309V. A capacitor from IMON to ground is required to filter higher frequency components. If V
BGATE (Pin 15):
Drives the bottom external N-channel BAT < 2.5V/cell, then V(I MOSFET of the battery charger buck converter. MON) = 1.19V when conditioning a depleted battery. Any current sourced or sinked from this
INFET (Pin 16):
Drives the Gate of the External Input PFET. pin directly affects the charging current accuracy. If this pin is to be monitored, a high impedance input buffer should be used.
TEST CIRCUIT
LTC4006 11.67µA + VREF + – EA 3k 35mV – BAT CSP ITH 10 9 7 + LT1055 – 0.6V 4006 TC 4006fa 6