AAT3688IWP-4.2-T1 查看數據表（PDF） - Advanced Analogic Technologies

零件编号

产品描述 (功能)

生产厂家

AAT3688IWP-4.2-T1

USB Port Lithium-Ion/Polymer Battery Charger

Advanced Analogic Technologies 

BatteryManagerTM

PRODUCT DATASHEET

AAT3688

USB Port Lithium-Ion/Polymer Battery Charger

Application Information

USB System Power Charging

The USB charge mode provides two programmable fast

charge levels up to 500mA for each, USB high and USB

low, USBH and USBL, respectively. The USBH or USBL

modes may be externally selected by the USB select pin

(USBSEL). When the USBSEL pin is connected to a logic

high level, the USBH level will be active. Conversely,

when USBSEL is pulled to a logic low level (ground), the

USBL level will be used for fast charging. Typically USBH

is set for 500mA and USBL is set for 100mA. However,

these two USB charge levels may be user programmed

to any level between 50mA and 500mA by selecting the

appropriate resistor values for RSETH and RSETL. Refer to

Table 1 for recommended RSETH and RSETL values for the

desired USB input constant current charge levels.

USB Charge Reduction

In many instances, product system designers do not

know the real properties of a potential USB port to be

used to supply power to the battery charger. Typical

powered USB ports commonly found on desktop and

notebook PCs should supply up to 500mA. In the event

a USB port being used to supply the charger is unable to

provide the programmed fast charge current, or if the

system under charge must also share supply current

with other functions, the AAT3688 will automatically

reduce USB fast charge current to maintain port integ-

rity and protect the host system.

The USB charge reduction system becomes active when

the voltage on the USB input falls below the USB charge

reduction threshold (VUSBCHR), which is typically 4.5V.

Regardless of which USB charge function is selected

(USBH or USBL), the charge reduction system will

reduce the fast charge current level in a linear fashion

until the voltage sensed on the USB input recovers

above the charge reduction threshold voltage. The USB

charge reduction threshold (VUSBCHR) may be externally

set to a value lower than 4.5V by placing a resistor

divider network between VUSB and ground with the center

connected to the CHR pin. The USB charge reduction

feature may be disabled by connecting a 10kΩ resistor

from the CHR pin directly to the USB input pin.

The following equation may be used to approximate a

USB charge reduction threshold below 4.5V:

Eq.

1:

VUSBCHR = 2.0V ÷

R12

R12 + R11

where R11/R12 << 1MΩ.

USBH

USBL

ICC

RSET (kΩ)

RSET (kΩ)

50

86.6

86.6

75

57.6

57.6

100

42.2

42.2

200

21.0

20.5

300

13.7

13.7

400

10.2

10.2

500

8.06

8.06

Table 1: Recommended RSET Values.

VUSB

USB

R11

CHR

R12

1.025M

VCHR = 2.0V

825k

Figure 2: Internal Equivalent Circuit

for the CHR Pin.

USB Input Charge Inhibit and Resume

The AAT3688 UVLO and power on reset feature will func-

tion when the USB input pin voltage level drops below

the UVLO threshold. At this point, the charger will sus-

pend charging and shut down. When power is re-applied

to the USB pin or the UVLO condition recovers, the sys-

tem charge control will assess the state of charge on the

battery cell and will automatically resume charging in

the appropriate mode for the condition of the battery.

Enable / Disable

The AAT3688 provides an enable function to control the

charger IC on and off. The enable (EN) pin is an active

high. When pulled to a logic low level, the AAT3688 will

be shut down and forced into the sleep state. Charging

will be halted regardless of the battery voltage or charg-

ing state. When the device is re-enabled, the charge

3688.2007.12.1.6

www.analogictech.com

13

Share Link: