MAX1873S Просмотр технического описания (PDF) - Maxim Integrated

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MAX1873S

Simple Current-Limited Switch-Mode Li+ Charger Controller

Maxim Integrated 

Simple Current-Limited Switch-Mode

Li+ Charger Controller

VIN 17V TO 28V

(9V MIN FOR 2- CELLS)

D1

MBR5340

CVL

2.2µF

CVH

0.22µF

VL

VH

CSSP

CDCIN

0.22µF

DCIN

CSSN

DISABLE

N

4V OUT PER

200mV ON RCSB

CCC

100kΩ 47nF

CCCS

47nF

CCCVS

0.1µF

RCCV

10kΩ

MAX1873

IOUT

EXT

ICHG/EN

CSB

CCI

BATT

REF

CCS

VADJ

CCV

GND

RP

4.7Ω

CP

0.01µF

RN

4.7Ω

RCSS

0.033Ω

CN

0.01µF

D2

MBR5340

P

L1

10µH

RCSB

0.068Ω

CREF

1µF

R1

R2

SYSTEM

LOAD

CL

47µF

CBATT

68µF

LI+

BATTERY

(2- TO 4-CELLS)

CCCVP

1nF

Figure 1. Typical Application Circuit

Detailed Description

The MAX1873 includes all of the functions necessary to

charge 2-, 3-, or 4-series cell lithium-ion (Li+) battery

packs. It includes a high-efficiency step-down DC-DC

converter that controls charging voltage and current. It

also features input source current limiting so that an AC

adapter that supplies less than the total system current

in addition to charging current can be used without fear

of overload.

The DC-DC converter uses an external P-channel MOS-

FET switch, inductor, and diode to convert the input volt-

age to charging current or charging voltage. The typical

application circuit is shown in Figure 1. Charging current

is set by RCSB, while the battery voltage is measured at

BATT. The battery regulation voltage limit is nominally

set to 8.4V for the R version (2-cells), 12.6V for the S

version (3-cells), and 16.8V for the T version (4-cells),

but it can also be adjusted to other voltages for differ-

ent Li+ chemistries.

Voltage Regulator

Li+ batteries require a high-accuracy voltage limit while

charging. The battery regulation voltage is nominally

set to 4.2V per cell and can be adjusted ±5.25% by

setting the voltage at VADJ between REF and ground.

By limiting the adjust range of the regulation voltage, an

overall voltage accuracy of better than ±0.75% is main-

tained while using 1% resistors.

An internal error amplifier maintains voltage regulation

to within ±0.75%. The amplifier is compensated at CCV

(see Figure 1). Individual compensation of the voltage

regulation and current regulation loops allows for opti-

mal compensation of each. A typical CCV compensa-

tion network is shown in Figure 1 and will suffice for

most designs.

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