LTC4088EDE-2 데이터 시트보기 (PDF) - Linear Technology

부품명

상세내역

제조사

LTC4088EDE-2

High Efficiency Battery Charger/USB Power Manager with Regulated Output Voltage

Linear Technology 

LTC4088-1/LTC4088-2

Operation

Ideal Diode from BAT to VOUT

The LTC4088-1/LTC4088-2 has an internal ideal diode as

well as a controller for an external ideal diode. Both the

internal and the external ideal diodes are always on and

will respond quickly whenever VOUT drops below BAT.

If the load current increases beyond the power allowed

from the switching regulator, additional power will be

pulled from the battery via the ideal diodes. Furthermore,

if power to VBUS (USB or wall power) is removed, then

all of the application power will be provided by the bat-

tery via the ideal diodes. The ideal diodes will be fast

enough to keep VOUT from drooping with only the stor-

age capacitance required for the switching regulator. The

internal ideal diode consists of a precision amplifier that

activates a large on-chip MOSFET transistor whenever

the voltage at VOUT is approximately 15mV (VFWD) below

the voltage at BAT. Within the amplifier’s linear range, the

small-signal resistance of the ideal diode will be quite low,

keeping the forward drop near 15mV. At higher current

levels, the MOSFET will be in full conduction. An external

P-channel MOSFET transistor should be added from BAT

to VOUT. The GATE pin of the LTC4088-1/LTC4088-2 drives

the gate of the external P-channel MOSFET transistor for

automatic ideal diode control. The source of the external

P-channel MOSFET should be connected to VOUT and the

2200

2000

1800

1600

1400

1200

1000

VISHAY Si2333

EXTERNAL

IDEAL DIODE

LTC4088-1/

LTC4088-2

IDEAL DIODE

800

600

400

200

0

0

ON

SEMICONDUCTOR

MBRM120LT3

VBUS = 5V

60 120 180 240 300 360 420 480

FORWARD VOLTAGE (mV) (BAT – VOUT)

408812 F03

Figure 3. Ideal Diode V-I Characteristics

drain should be connected to BAT. Capable of driving a

1nF load, the GATE pin can control an external P-channel

MOSFET transistor having an on-resistance of 30mΩ or

lower. When VBUS is unavailable, the forward voltage of

the ideal diode amplifier will be reduced from 15mV to

nearly zero.

Suspend LDO

The LTC4088-1/LTC4088-2 provides a small amount of

power to VOUT in SUSPEND mode by including an LDO

from VBUS to VOUT. This LDO will prevent the battery from

running down when the portable product has access to a

suspended USB port. Regulating at 4.6V, this LDO only

becomes active when the switching converter is disabled.

To remain compliant with the USB specification, the input

to the LDO is current limited so that it will not exceed the

low power or high power suspend specification. If the load

on VOUT exceeds the suspend current limit, the additional

current will come from the battery via the ideal diodes. The

suspend LDO sends a scaled copy of the VBUS current to

the CLPROG pin, which will servo to approximately 100mV

in this mode. Thus, the high power and low power suspend

settings are related to the levels programmed by the same

resistor for 1x and 5x modes.

VBUS Undervoltage Lockout (UVLO)

An internal undervoltage lockout circuit monitors VBUS and

keeps the switching regulator off until VBUS rises above the

rising UVLO threshold (4.3V). If VBUS falls below the falling

UVLO threshold (4V), system power at VOUT will be drawn

from the battery via the ideal diodes. The voltage at VBUS

must also be higher than the voltage at BAT by approxi-

mately 170mV for the switching regulator to operate.

Battery Charger

The LTC4088-1/LTC4088-2 includes a constant-current/

constant-voltage battery charger with automatic recharge,

automatic termination by safety timer, low voltage trickle

charging, bad cell detection and thermistor sensor input

for out of temperature charge pausing.

40881fc

12

Share Link: