LTC4010CFE datasheet(17/24 Pages) LINER

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LTC4010

4010fb

Sample Applications

Figures 6 through 8 detail sample charger applications of

variouscomplexities.CombinedwiththeTypicalApplication

on the first page of this data sheet, these figures demon-

strate some of the proper configurations of the LTC4010.

MOSFET body diodes are shown in these figures strictly

for reference only.

Figure 6 shows a minimum application, which might be

encountered in low cost NiCd fast charge applications.

The LTC4010 uses –∆V to terminate the fast charge state,

as no external temperature information is available.

Nonsynchronous PWM switching is employed to reduce

external component cost. A single LED indicates charging

status.

Afull-featured2ALTC4010applicationisshowninFigure 7.

The inherent voltage ratings of the VCELL, VCDIV, SENSE

and BAT pins allow charging of one to sixteen series nickel

cellsinthisapplication,governedonlybytheVCCoverhead

limits previously discussed. The application includes all

average cell voltage and battery temperature sensing

circuitry required for the LTC4010 to utilize its full range

of charge qualification, safety monitoring and fast charge

terminationfeatures.TheVTEMPthermisternetworkallows

the LTC4010 to accurately terminate fast charge under a

applicaTions inForMaTion

varietyofappliedchargerates.UseofasynchronousPWM

topology improves efficiency and reduces excess heat

generation. LED D1 indicates valid DC input voltage and

installed battery, while LED D2 indicates charging. Fault

conditions are indicated by LED D3. The grounded CHEM

pin selects the NiMH charge termination parameter set.

P-channelMOSFETQ1functionsasaswitchtoconnectthe

battery to the system load whenever the DC input adapter

is removed. If the maximum battery voltage is less than

the maximum rated VGS of Q1, diode D4 and resistor R1

are not required. Otherwise choose the Zener voltage

of D4 to be less than the maximum rated VGS of Q1. R1

provides a bias current of (VBAT – VZENER)/(R1 + 20k) for

D4 when the input adapter is removed. Choose R1 to make

this current, which is drawn from the battery, just large

enough to develop the desired VGS across D4.

While the LTC4010 is a complete, standalone solution,

Figure 8 shows that it can also be interfaced to a host

microprocessor. The host MCU can control the charger

directlywithanopen-drainI/OportconnectedtotheVTEMP

pin, if that port is low leakage and can tolerate at least

2V. The charger state is monitored on the three LTC4010

status outputs. Charging of NiMH batteries is selected in

this example. However, NiCd parameters could be chosen

as well.

Figure 6. Minimum 1 Amp LTC4010 Application

FAULT

CHRG

READY

VCC

TGATE

VCDIV

VCELL

CHEM

VTEMP

LTC4010

TIMER

INTVDD

GND

SENSE

BAT

FROM

ADAPTER

12V

10µH

SYSTEM

LOAD

0.1

NiCd

PACK

(1AHr)

4010 F06

49.9k

10k

8.66k

0.1µF

10µF

33nF

10µF

BGATE

PGND

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