User manual

LTC4100
17
4100fb
OPERATION
9. There is insuffi cient DCIN voltage to charge the battery.
The LTC4100 will resume wake-up charging when there
is suffi cient DCIN voltage to charge the battery. This
condition will not reset the T
TIMEOUT
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 qualifi ed by DCDIV >
V
ACP
.
The following conditions will stop the controlled charging
algorithm and will cause the battery charger controller to
stop charging:
1. The ChargingCurrent() AND ChargingVoltage() functions
have not been written for T
TIMEOUT
.
2. The SafetySignal is registering RES_OR.
3. The SafetySignal is registering RES_HOT.
4. The AC power is no longer present. (DCDIV < V
ACP
)
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. Insuffi cient DCIN voltage to charge the battery. The
LTC4100 will resume charging using the previous
ChargingVoltage() AND ChargingCurrent() function
values, when there is suffi cient 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 R
THA
is 1.13k and R
THB
is 54.9k.
Figure 4. SafetySignal Decoder Block
R
THA
1.13k
R
SafetySignal
R
THB
54.9k
V
DD
V
DD
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
C
SS
16
15
Figure 5. Simplifi ed V
LIM
Circuit Concept (I
LIM
is Similar)
V
LIM
12.5k
25k
33k
25k
25k
12.5k
R
VLIM
V
DD
V
LIM
[3:0]
4100 F05
AC_PRESENT
4
+
–
+
–
+
–
+
–
ENCODER
14