Rainbow-electronics MAX8903A Bedienungsanleitung PDF herunterladen (Seite 20)

MAX8903A

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

and Adapter Power

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

raises the cold threshold, while only slightly raising the

hot threshold. Raising R

lowers both the hot and cold

thresholds, while lowering R

raises both thresholds.

Note that since VL is active whenever valid input power

is connected at DC or USB, thermistor bias current

flows at all times, even when charging is disabled (CEN

= high). When using a 10kΩ thermistor and a 10kΩ

pullup to VL, this results in an additional 250µA load.

This load can be reduced to 25µA by instead using a

100kΩ thermistor and 100kΩ pullup resistor.

Power Dissipation

PCB Layout and Routing

Good design minimizes ground bounce and voltage

gradients in the ground plane, which can result in insta-

bility or regulation errors. The GND and PGs should

connect to the power-ground plane at only one point to

minimize the effects of power-ground currents. Battery

ground should connect directly to the power-ground

plane. The ISET and IDC current-setting resistors

should connect directly to GND to avoid current errors.

Connect GND to the exposed pad directly under the IC.

Use multiple tightly spaced vias to the ground plane

under the exposed pad to help cool the IC. Position

input capacitors from DC, SYS, BAT, and USB to the

power-ground plane as close as possible to the IC.

Keep high current traces such as those to DC, SYS,

and BAT as short and wide as possible. Refer to the

MAX8903A Evaluation Kit for a suitable PCB layout

example.

28-PIN 4mm x 4mm THIN QFN

SINGLE-LAYER PCB MULTILAYER PCB

Continuous

Power

Dissipation

1666.7mW

Derate 20.8mW/°C

above +70°C

2286mW

Derate 28.6mW/°C

above +70°C

48°C/W 35°C/W

3°C/W 3°C/W

Table 4. Package Thermal Characteristics

MAX8903A

THIN QFN

4mm x 4mm

TOP VIEW

DCM

BST

IUSB

BAT

FLT

USB

BAT

THM

USUS

4567

2021 19 17 16 15

GND

IDC

UOK

DOK

SYS

ISET

SYS

CEN

CHG

*EXPOSED PAD

*EP

Pin Configuration

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns, go

to www.maxim-ic.com/packages

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 TQFN-EP T2844-1

21-0139

1 2 ... 15 16 17 18 19 20

MAX8903A 1

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