LTC4088 LINER [Linear Technology], LTC4088 Datasheet - Page 7

• Manufacturer Part Number: LTC4088
• Description: High Effi ciency Battery Charger/USB Power Manager
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
TYPICAL PERFOR A CE CHARACTERISTICS
NTC (Pin 1): Input to the NTC Thermistor Monitoring
Circuits. The NTC pin connects to a negative temperature
coeffi cient thermistor which is typically co-packaged with
the battery pack to determine if the battery is too hot or
too cold to charge. If the battery’s temperature is out of
range, charging is paused until the battery temperature re-
enters the valid range. A low drift bias resistor is required
from V
to ground. If the NTC function is not desired, the NTC pin
should be grounded.
CLPROG (Pin 2): USB Current Limit Program and Monitor
Pin. A 1% resistor from CLPROG to ground determines
the upper limit of the current drawn from the V
A precise fraction of the input current, h
to the CLPROG pin when the high side switch is on. The
switching regulator delivers power until the CLPROG
pin reaches 1.188V. Therefore, the current drawn from
V
R
two of which correspond to the 500mA and 100mA USB
specifi cations. A multilayer ceramic averaging capacitor
is also required at CLPROG for fi ltering.
BUS
CLPROG
100
U
80
40
20
60
0
0
will be limited to an amount given by h
CHRG Pin Current vs Voltage
(Pull-Down State)
V
V
BUS
BUS
BAT
. There are several ratios for h
= 3.8V
= 5V
U
to NTC and a thermistor is required from NTC
1
CHRG PIN VOLTAGE (V)
2
U
3
W
4
4088 G19
U
5
AC COUPLED
CLPROG
20mV/DIV
5mA/DIV
V
I
CLPROG
LDO3V3
LDO3V3
0mA
CLPROG
V
3.3V LDO Transient Response
(5mA to 15mA)
available,
BAT
, is sent
BUS
= 3.8V
pin.
and
20µs/DIV
LDO3V3 (Pin 3): LDO Output. The LDO3V3 pin provides
a regulated, always-on 3.3V supply voltage. This pin gets
its power from V
as a real-time clock or housekeeping microprocessor. A
1µF capacitor is required from LDO3V3 to ground if it will
be called upon to deliver current. If the LDO3V3 output is
not used it should be disabled by connecting it to V
D2 (Pin 4): Mode Select Input Pin. D2, in combination
with the D0 pin and D1 pin, controls the current limit and
battery charger functions of the LTC4088 (see Table 1).
This pin is pulled low by a weak current sink.
C/X (Pin 5): End of Charge Indication Program Pin. This pin
is used to program the current level at which a completed
charge cycle is indicated by the ⎯ C ⎯ H ⎯ R ⎯ G pin.
PROG (Pin 6): Charge Current Program and Charge Cur-
rent Monitor Pin. Connecting a 1% resistor from PROG
to ground programs the charge current. If suffi cient input
power is available in constant-current mode, this pin servos
to 1V. The voltage on this pin always represents the actual
charge current by using the following formula:
I
BAT
=
R
V
PROG
PROG
T
A
4088 G20
= 25°C unless otherwise noted.
OUT
• 1031
AC COUPLED
500
20mV/DIV
. It may be used for light loads such
µ
A/DIV
V
0mA
I
OUT
OUT
Suspend LDO Transient Response
(500µA to 1mA)
500
LTC4088
µ
s/DIV
OUT
7
4088 G21
4088f
.