ltc4069edc-trpbf Linear Technology Corporation, ltc4069edc-trpbf Datasheet - Page 6

• Manufacturer Part Number: ltc4069edc-trpbf
• Description: Standalone 750ma Li-ion Battery Charger In 2 X 2 Dfn With Ntc Thermistor Input
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
LTC4069
GND (Pin 1): Ground.
CHRG (Pin 2): Open-Drain Charge Status Output. The
charge status indicator pin has three states: pull-down,
pulse at 2Hz and high impedance state. This output can be
used as a logic interface or as an LED driver. When the
battery is being charged, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge current
drops to 10% of the full-scale current, the CHRG pin is
forced to a high impedance state. If the battery voltage
remains below 2.9V for one quarter of the charge time, the
battery is considered defective and the CHRG pin pulses at
a frequency of 2Hz (75% duty cycle). When the NTC pin
voltage rises above 0.76 • V
the CHRG pin pulses at a frequency of 2Hz (25% duty
cycle).
BAT (Pin 3): Charge Current Output. Provides charge
current to the battery and regulates the final float voltage
to 4.2V. An internal precision resistor divider on this pin
sets the float voltage and is disconnected in shutdown
mode.
V
provides power to the charger. V
to 5.5V. This pin should be bypassed with at least a 1µF
capacitor. When V
voltage, the LTC4069 enters shutdown mode, dropping
I
6
BAT
CC
U
to about 1µA.
(Pin 4): Positive Input Supply Voltage. This pin
U
CC
U
is within 32mV of the BAT pin
CC
or drops below 0.35 • V
CC
can range from 3.75V
CC
,
NTC (Pin 5): Input to the NTC (Negative Temperature
Coefficient) Thermistor Temperature Monitoring Circuit.
Under normal operation, connect a thermistor from the
NTC pin to ground and a resistor of equal value from the
NTC pin to V
0.35 • V
cold, charging is suspended, the internal timer is frozen
and the CHRG pin output will start to pulse at 2Hz. Pulling
this pin below 0.016 • V
is approximately 3°C of temperature hysteresis associ-
ated with each of the input comparator’s thresholds.
PROG (Pin 6): Charge Current Program and Charge Cur-
rent Monitor Pin. Connecting a 1% resistor, R
ground programs the charge current. When charging in
constant-current mode, this pin servos to 1V. In all modes,
the voltage on this pin can be used to measure the charge
current using the following formula:
Floating the PROG pin puts the charger in shutdown mode.
In shutdown mode, the LTC4069 has less than 20µA
supply current and about 1µA battery drain current.
Exposed Pad (Pin 7): Ground. The Exposed Pad must be
soldered to the PCB ground to provide both electrical con-
tact and rated thermal performance.
I
BAT
CC
=
R
at hot temperatures or rises above 0.76 • V
V
PROG
PROG
CC
. When the voltage at this pin drops below
• 1000
CC
disables the NTC feature. There
PROG
CC
4069fa
, to
at