LTC4100
8
4100fc
For more information www.linear.com/LTC4100
pin FuncTions
V
LIM
(Pin 14): An external resistor is connected between
this pin and GND. The value of the external resistor pro-
grams the
range and resolution of the charging voltage.
This is a digital, not an analog, function.
THB
(Pin 15): SafetySignal Force/Sense Pin to Smart
Battery. See description of operation for more detail. The
maximum allowed combined capacitance on THA, THB and
SafetySignal is 1nF (see Figure 4). A series resistor 54.9k
needs to be connected between this pin and the battery’s
SafetySignal for this circuit to work correctly.
THA (Pin 16): SafetySignal Force/Sense Pin to Smart
Battery. See description of operation for more detail. The
maximum allowed combined capacitance on THA, THB
and SafetySignal is 1nF (see Figure 4). A series resistor
1130Ω needs to be connected between this pin and the
battery’s SafetySignal for this circuit to work correctly.
V
DD
(Pin 17): Power Supply Input for the LTC4100 Digital
Circuitry. Bypass this pin with 0.1µF. Typically between
3.3V and 5V
DC
.
V
SET
(Pin 18): Tap Point of the Programmable Resistor
Divider, which Provides Battery Voltage Feedback to the
Charger.
I
TH
(Pin 19): Control Signal of the Inner Loop of the Current
Mode PWM. Higher I
TH
corresponds to higher charging
current in normal operation. A 0.0015µF capacitor to GND
filters out PWM ripple. Typical full-scale output current
is 40µA. Nominal voltage range for this pin is 0V to 3V.
I
DC
(Pin 20): Bypass to GND with a 0.068µF Capacitor.
CSP (Pin 21): Current Amplifier CA1 Input. This pin and
the BAT pin measure the voltage across the sense resis
-
tor, R
SENSE
, to provide the instantaneous current signals
required for both peak and average current mode operation.
BAT (Pin 22): Battery Sense Input and the Negative Refer
-
ence for the Current Sense Resistor. A bypass capacitor
of at least 10µF is required.
CLN (Pin 23): Negative Input to the Input Current Limiting
Circuit Block. If no current limit function is desired, connect
this pin to CLP. The threshold is set at 100mV below the
voltage at the CLP pin. When used to limit supply current,
a filter is needed to filter out the switching noise.
CLP (Pin 24): Positive Input to the Input Current Limiting
Circuit Block. This pin also serves as a power supply for
the IC.
