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LTC4100

4100fb

OPERATION

9. There is insufﬁcient DCIN voltage to charge the battery.

The LTC4100 will resume wake-up charging when there

is sufﬁcient DCIN voltage to charge the battery. This

condition will not reset the TTIMEOUT timer.

Controlled Charging Algorithm Overview

The following conditions must be met in order to allow

controlled charging to start on the LTC4100:

1. The ChargingVoltage() AND ChargingCurrent() function

must be written to non-zero values.

2. The SafetySignal must be RES_COLD, RES_IDEAL, or

RES_UR.

3. AC must be present. This is qualiﬁed by DCDIV >

VACP.

The following conditions will stop the controlled charging

algorithm and will cause the battery charger controller to

stop charging:

1. TheChargingCurrent()ANDChargingVoltage()functions

have not been written for TTIMEOUT.

2. The SafetySignal is registering RES_OR.

3. The SafetySignal is registering RES_HOT.

4. The AC power is no longer present. (DCDIV < VACP)

5. ALARM_INHIBITED is set in the ChargerStatus()

function.

6. INHIBIT_CHARGE is set in the ChargerMode() function.

Clearing INHIBIT_CHARGE will cause the LTC4100 to

resume charging using the previous ChargingVoltage()

AND ChargingCurrent() function values.

7. RESET_TO_ZERO is set in the ChargerMode() function.

8. CHGEN pin is pulled low by an external device. The

LTC4100 will resume charging using the previous

ChargingVoltage() AND ChargingCurrent() function

values, if the CHGEN pin is released by the external

device.

9. Insufﬁcient DCIN voltage to charge the battery. The

LTC4100 will resume charging using the previous

ChargingVoltage() AND ChargingCurrent() function

values, when there is sufﬁcient DCIN voltage to charge

the battery.

10. Writing a zero value to ChargingVoltage() function.

11. Writing a zero value to ChargingCurrent() function.

The SafetySignal Decoder Block

This block measures the resistance of the SafetySignal and

features high noise immunity at critical trip points. The low

power standby mode supports only battery presence SMB

charger reporting requirements when AC is not present.

The SafetySignal decoder is shown in Figure 4. The value

of RTHA is 1.13k and RTHB is 54.9k.

Figure 4. SafetySignal Decoder Block

RTHA

1.13k

RSafetySignal

RTHB

54.9k

VDD

4100 F04

THA_SELB

THB_SELB

RES_OR

RES_COLD

RES_H0T

RES_UR

LATCH

SafetySignal

CONTROL

MUX

REF

HI_REF

LO_REF

TH_HI

TH_LO

THA

THB

CSS

Figure 5. Simpliﬁed VLIM Circuit Concept (ILIM is Similar)

VLIM

12.5k

25k

33k

25k

12.5k

RVLIM

VDD

VLIM [3:0]

4100 F05

AC_PRESENT

ENCODER

LTC4100 Datasheet(PDF) 17 Page - Linear Technology

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