Rainbow-electronics MAX8903A Bedienungsanleitung PDF herunterladen (Seite 13)

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*

and Adapter Power

______________________________________________________________________________________ 13

The IC includes a full-featured charger with thermistor

monitor, fault timer, charger status, and fault outputs.

Also included are power-OK signals for both USB and

DC. Flexibility is maintained with adjustable charge

current, input current limit, and a minimum system volt-

age (when charging is scaled back to hold the system

voltage up).

The MAX8903A prevents overheating during high ambi-

ent temperatures by limiting charging current when the

die temperature exceeds +100°C.

DC Input—Fast Hysteretic

Step-Down Regulator

If a valid DC input is present, the USB power path is

turned off and power for SYS and battery charging is

supplied by the high-frequency step-down regulator

from DC. If the battery voltage is above the minimum

system voltage (V

SYSMIN

, Figure 4), the battery charger

connects the system voltage to the battery for lowest

power dissipation. The step-down regulation point is

then controlled by three feedback signals: maximum

BST

SYS

BAT

FLT

UOK

DOK

FAULT

OUTPUT

USB PWR OK

DC PWR OK

TO VL

4 x 100kΩ

17 USB

ISET

IDC

ISET

IDC

DCM

THM

CEN

IUSB

GND

NTC

10kΩ

USUS

CHARGE ON

OFF

100mA

500mA

USB SUSPEND

TO SYSTEM

LOAD

CHG

CHARGE

INDICATOR

4.7μF

0.15μF

1μH

BST

0.1μF

10kΩ

TO SYSTEM LOGIC

1-CELL

LI+

BAT

10μF

SYS

10μF

MAX8903A

VBUS

D-

D+

GND

SERIES

MINI-B

1μF

Figure 3. Typical Application Circuit Using a Mini 5 Style Connector or Other DC/USB Common Connector

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 19 20

MAX8903A 1

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