LTM8062

13

8062f

APPLICATIONS INFORMATION

voltage characteristic is slightly nonlinear. This nonlinear

characteristic follows the relation:

(with a 2.18V minimum)

where T = temperature in °C. A thermistor-based network

can be used to approximate the nonlinear ideal tempera-

ture characteristic across a reasonable operating range,

as shown in Figure 6.

Status Pins

The LTM8062 reports charger status through two open-

collector outputs, the CHRG and FAULT pins. These pins

The CHRG pin indicates that the charger is delivering

current at greater than a C/10 rate, or one-tenth of the

programmed charge current. The FAULT pin signals bad-

battery and NTC faults. These pins are binary coded, as

shown in Table 3.

Table 3. Status Pin State

CHRG

FAULT

STATUS

High

High

Not Charging—Standby or Shutdown Mode

High

Low

Bad-Battery Fault (Precondition Timeout/EOC Failure)

Low

High

Normal Charging at C/10 or Greater

Low

Low

NTC Fault (Pause)

If the battery is removed from an LTM8062 charger that is

configured for C/10 termination, a low amplitude sawtooth

waveform appears at the charger output, due to cycling

between termination and recharge events. This cycling

results in pulsing at the CHRG output. An LED connected

to this pin will exhibit a blinking pattern, indicating to the

user that a battery is not present. The frequency of this

blinking pattern is dependent on the output capacitance.

C/10 Charge Termination

The LTM8062 supports a low current based termination

scheme, where a battery charge cycle terminates when

the charge current falls below one-tenth the programmed

charge current, or approximately 200mA. This termination

mode is engaged by shorting the TMR pin to ground. When

C/10 termination is used, an LTM8062 charger sources

battery charge current as long as the average current level

remains above the C/10 threshold. As the full-charge float

voltage is achieved, the charge current falls until the C/10

threshold is reached, at which time the charger terminates

and the LTM8062 enters standby mode. The CHRG status

pin follows the charger cycle and is high impedance when

the charger is not actively charging. There is no provision

for bad-battery detection if C/10 termination is used.

Timer Charge Termination

The LTM8062 supports a timer-based termination scheme,

where a battery charge cycle terminates after a specific

amount of time elapses. Timer termination is engaged

to Closely Match Ideal Lead-Acid Float Charge Voltage for 6-Cell Charger

TEMPERATURE (°C)

–10

10

50

40

60

020

30

8062 F06b

12.8

13.0

13.2

13.4

13.6

13.8

14.0

14.6

14.4

14.2

14.8

8062 F06a

LTM8062

196k

69k

22k

B = 3380

69k

BAT

ADJ

198k

6-CELL

LEAD-ACID

BATTERY

+