MAX8600 Просмотр технического описания (PDF) - Maxim Integrated

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MAX8600

Single-/Dual-Input 1-Cell Li+ Chargers with OVP Protection and Programmable Charge Timer

Maxim Integrated 

Single-/Dual-Input 1-Cell Li+ Chargers with

OVP Protection and Programmable Charge Timer

Detailed Description

DC Charging

The MAX8600/MAX8601 are designed to charge a sin-

gle-cell Li+ battery from a DC source voltage between

4.15V and 7V. The precharge current, charge current,

and top-off threshold are programmable with RSETI.

USB Charging (MAX8601)

The MAX8601 contains a USB input that allows opera-

tion from either a DC source or a USB port. A USEL input

allows the user to select either a 100mA or 500mA maxi-

mum charging current when using the USB input. If both

VUSB and VDC are valid, the MAX8601 operates from

DC. If VDC is invalid (undervoltage/overvoltage), the

MAX8601 operates from USB. When charging at 100mA

from the USB input, the fast-charge timer is inhibited.

EN Charger-Enable Input

EN is a logic input (active low) that enables the charger.

Drive EN high to disable the charger-control circuitry.

Drive EN low or connect to GND for normal operation.

Soft-Start

To prevent input transients, the rate of change of

charging current is limited. When the charger is turned

on or when the input source is changed, charge current

is ramped from 0 to the set current value in typically

1.2ms. This also means that if charging is taking place

from USB, and the DC input is then powered, charge

current falls to zero and then is reramped to the DC

charge rate. This is done to ensure that the DC source

is not subjected to a severe load current step.

Charge-current ramp up is also limited when transition-

ing from prequal to fast-charge, and when changing

the USB charge current from 100mA to 500mA with

USEL. There is no di/dt limiting, however, if ISET is

changed suddenly using a switch at RSETI.

Thermal-Limit Control

The MAX8600/MAX8601 feature a thermal limit that

reduces the charge current when the die temperature

exceeds +100°C. As the temperature increases above

+100°C, the IC lowers the charge current by 5%/°C.

CHG Charge-Indicator Output

CHG is an open-drain output that indicates charger sta-

tus. CHG goes low during charge cycles where VBAT is

greater than 3V and IBAT is greater than 7.5% of the

maximum charge current set by RSETI. When the

MAX8600/MAX8601 are used in conjunction with a

microprocessor (µP), connect a pullup resistor between

CHG and the logic I/O voltage to indicate charge status

to the µP. Alternatively, CHG can sink up to 20mA for

an LED charge indicator.

Fault Indicator (FLT)

The MAX8600/MAX8601 contain an open-drain FLT

output to signal the user when a fault occurs. FLT goes

low if the charger is in prequal and the prequal timer

expires, or if the charger is in fast-charge and the fast-

charge time expires. FLT does NOT go low if the THM

thermistor temperature is out of range. Toggle EN or

the input power to reset the FLT indicator.

Power-OK Indicator (POK)

The MAX8600/MAX8601 contain an open-drain POK out-

put that goes low when a valid input source is detected

at DC or USB (MAX8601 only). A valid input source is

one whose voltage is between 4.15V and 7V and

exceeds the battery voltage by 320mV. After a valid

input has been established, charging is sustained with

inputs as low as 3.5V as long as the input voltage

remains above the battery voltage by at least 55mV (typ).

POK is high impedance when the charger is disabled.

Applications Information

Figure 2 shows the typical operating circuit for the

MAX8601. The following section describes component

changes for different charging current and timer durations.

AC ADAPTER

4.5V TO 7V

(OVP TO 16V)

1μF

USB PORT

4.5V TO 5.5V

500mA

100mA

OFF

ON

RSETI

2kΩ

TO LOGIC

SUPPLY

(3.3V)

DC

FLT

POK

GND

CHG

BAT

USB

MAX8601 THM

USEL

EN

CT

SETI

100kΩ 100kΩ 330Ω

FAULT

POWER-OK

2.2μF

NTC

10kΩ AT

+25°C

CCT

0.068μF

Figure 2. Typical Operating Circuit for USB/AC-Adapter Input

Charger. An RSETI of 2kΩ sets an AC adapter fast-charge of

750mA.

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