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,

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

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

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-

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.

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

OVP Protection and Programmable Charge Timer

_______________________________________________________________________________________

7

BAT

NTC

10k

Ω AT

+25

°C

2k

Ω

CT

THM

AC ADAPTER

4.5V TO 7V

(OVP TO 16V)

USB PORT

4.5V TO 5.5V

GND

USB

EN

OFF

ON

FLT

TO LOGIC

SUPPLY

(3.3V)

100k

Ω

100k

Ω

330

Ω

FAULT

POWER-OK

0.068

μF

1

μF

DC

SETI

USEL

POK

CHG

MAX8601

500mA

100mA

2.2

μF

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

Ω sets an AC adapter fast-charge of

750mA.