LTC4088EDE-PBF 데이터 시트보기 (PDF) - Linear Technology

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LTC4088EDE-PBF

High Efficiency Battery Charger/USB Power Manager

Linear Technology 

LTC4088

Typical Performance Characteristics TA = 25°C, unless otherwise noted.

CHRG Pin Current vs Voltage

(Pull-Down State)

100 VBUS = 5V

VBAT = 3.8V

80

3.3V LDO Transient Response

(5mA to 15mA)

ILDO3V3

5mA/DIV

Suspend LDO Transient Response

(500µA to 1mA)

IOUT

500µA/DIV

60

0mA

VLDO3V3

40

20mV/DIV

AC COUPLED

20

VBAT = 3.8V

20µs/DIV

0

0

1

2

3

4

5

CHRG PIN VOLTAGE (V)

4088 G19

0mA

VOUT

20mV/DIV

AC-COUPLED

4088 G20

500µs/DIV

4088 G21

Pin Functions

NTC (Pin 1): Input to the NTC Thermistor Monitoring

Circuits. The NTC pin connects to a negative temperature

coefficient 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 VBUS to NTC and a thermistor is required from NTC

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 VBUS pin.

A precise fraction of the input current, hCLPROG, is sent

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

VBUS will be limited to an amount given by hCLPROG and

RCLPROG. There are several ratios for hCLPROG available,

two of which correspond to the 500mA and 100mA USB

specifications. A multilayer ceramic averaging capacitor

is also required at CLPROG for filtering.

LDO3V3 (Pin 3): LDO Output. The LDO3V3 pin provides

a regulated, always-on 3.3V supply voltage. This pin gets

its power from VOUT. It may be used for light loads such

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 VOUT.

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 CHRG 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 sufficient 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:

IBAT

=

VPROG

RPROG

• 1031

4088fb

7

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