Datasheet

LTC4095
7
4095fa
SIMPLIFIED BLOCK DIAGRAM
–
+
–
+
6
+
–
RECHRG
CHRGR
ON
TEMP
FAULT
TERMINATE
CHARGE
BAD
BAT
TRICKLE
2.9V
M1
BAT
4.105V
NTC
3
CHRG
NTC
TRICKLE
CHARGE
TEMP FAULT
CONTROL
LOGIC
BLINK
LOGIC
COUNTER
2.25MHz CLOCK
CONSTANT CURRENT/
CONSTANT VOLTAGE
CHARGE
CURRENT
CONTROL
RECHARGE
–
+
C/10
100mV
PROG
I
BAT
ENABLE
I
BAT
800
T
REF
HPWR
T
DIE
5
IN
THERMAL
AMP
BAT
BAT
IN
4V
8
1
–
+
–
+
SUSP
4095 F01
4
7
GND
2
IN
DUVLO
UVLO
Figure 1. LTC4095 Block Diagram
OPERATION
Introduction
The LTC4095 is a linear battery charger designed to
charge single-cell lithium-ion batteries. The charger uses
a constant-current/constant-voltage charge algorithm
with a charge current programmable up to 950mA. Ad-
ditional features include automatic recharge, an internal
termination timer, low-battery trickle charge conditioning,
bad-battery detection, and a thermistor sensor input for
out of temperature charge pausing.
Futhermore, the LTC4095 is capable of operating from a
USB power source. In this application, charge current can
be programmed to a maximum of 100mA or 500mA per
USB power specifi cations.
Input Current vs Charge Current
The LTC4095 regulates the total current delivered to the
BAT pin; this is the charge current. To calculate the total
input current (i.e., the total current drawn from the IN pin),
it is necessary to sum the battery charge current, charger
quiescent current and PROG pin current.
Undervoltage Lockout (UVLO)
The undervoltage lockout circuit monitors the input volt-
age (IN) and disables the battery charger until IN rises
above V
UVLO
(typically 4V). 200mV of hysteresis prevents
oscillations around the trip point. In addition, a differential
undervoltage lockout circuit disables the battery charger
when IN falls to within V
DUVLO
(typically 40mV) of the
BAT voltage.
Suspend Mode
The LTC4095 can also be disabled by pulling the SUSP
pin above 1.2V. In suspend mode, the battery drain cur-
rent is reduced to 1.3µA and the input current is reduced
to 8.5µA.