LTC4000-1 Datasheet, PDF (8/40 Pages) Linear Technology – High Voltage High Current Controller for Battery Charging with Maximum Power Point Control

LTC4000-1
Pin Functions (QFN/SSOP)
VM (Pin 1/Pin 25): Voltage Monitor Input. High impedance
input to an accurate comparator with a 1.193V threshold
(typical). This pin controls the state of the RST output
pin. Connect a resistor divider (R_VM1, R_VM2) between the
monitored voltage and GND, with the center tap point con-
nected to this pin. The falling threshold of the monitored
voltage is calculated as follows:
V_{VM _ RST}
=
R_VM1 + R_VM2
R_VM2
• 1.193V
where R_VM2 is the bottom resistor between the VM pin
and GND. Tie to the BIAS pin if voltage monitoring func-
tion is not used.
RST (Pin 2/Pin 26): High Voltage Open Drain Reset Output.
When the voltage at the VM pin is below 1.193V, this status
pin is pulled low. When driven low, this pin can disable
a DC/DC converter when connected to the converter’s
enable pin. This pin can also drive an LED to provide a
visual status indicator of a monitored voltage. Short this
pin to GND when not used.
IIMON (Pin 3/Pin 27): Input Current Monitor. The voltage
on this pin is 20 times (typical) the sense voltage (V_IN,CLN)
across the input current sense resistor(R_IS), therefore
providing a voltage proportional to the input current.
Connect an appropriate capacitor to this pin to obtain a
voltage representation of the time-average input current.
Leave this pin open when input current monitoring func-
tion is not needed.
IFB (Pin 4/Pin 28): Input Voltage Feedback Pin. This pin is
a high impedance input pin used to sense the input voltage
level. In regulation, the input voltage loop sets the voltage
on this feedback pin to 1.000V. When the input feedback
voltage drops below 1.000V, the ITH pin is pulled down
to reduce the load on the input source. Connect this pin
to the center node of a resistor divider between the IN
pin and GND to set the input voltage regulation level. This
regulation level can then be obtained as follows:
V_{IN _ REG}
=


R_OFB1
R_OFB2
+
1^{}
•
1.000V
If the input voltage regulation feature is not used, connect
the IFB pin to the BIAS pin.
ENC (Pin 5/Pin 1): Enable Charging Pin. High impedance
digital input pin. Pull this pin above 1.5V to enable charg-
ing and below 0.5V to disable charging. Leaving this pin
open causes the internal 2µA pull-up current to pull the
pin to 2.5V (typical).
IBMON (Pin 6/Pin 2): Battery Charge Current Monitor. The
voltage on this pin is 20 times (typical) the sense voltage
(V_CSP,CSN) across the battery current sense resistor (R_CS),
therefore providing a voltage proportional to the battery
charge current. Connect an appropriate capacitor to this
pin to obtain a voltage representation of the time-average
battery charge current. Short this pin to GND to disable
charge current limit feature.
CX (Pin 7/Pin 3): Charge Current Termination Pro-
gramming. Connect the charge current termination pro-
gramming resistor (R_CX) to this pin. This pin is a high
impedance input to a comparator and sources 5μA of
current. When the voltage on this pin is greater than the
charge current monitor voltage (V_IBMON), the CHRG pin
40001f
8