LTC4100EG#TRPBF Linear Technology, LTC4100EG#TRPBF Datasheet - Page 18

• Manufacturer Part Number: LTC4100EG#TRPBF
• Description: IC SMART BATTERY CHARGER 24-SSOP
• Manufacturer: Linear Technology

Specifications of LTC4100EG#TRPBF

• Function: Charge Management
• Battery Type: Smart Batteries
• Voltage - Supply: 6 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4100
OPERATION
SafetySignal sensing is accomplished by a state machine
that reconfi gures the switches of Figure 4 using THA_SELB
and THB_SELB, a selectable reference generator, and two
comparators. This circuit has two modes of operation
based upon whether AC is present.
When AC is present, the LTC4100 samples the value of
the SafetySignal and updates the ChargerStatus register
approximately every 32ms. The state machine successively
samples the SafetySignal value starting with the RES_OR
≥ RES_COLD threshold, then RES_C0LD ≥ RES_IDEAL
threshold, RES_IDEAL ≥ RES_HOT threshold, and fi nally
the RES_HOT ≥ RES_UR threshold. Once the SafetySig-
nal range is determined, the lower value thresholds are
not sampled. The SafetySignal decoder block uses the
previously determined SafetySignal value to provide the
appropriate adjustment in threshold to add hysteresis.
The R
≥ RES_COLD and RES_COLD ≥ RES_IDEAL thresholds by
connecting the THB pin to V
resultant on the THA pin. The R
to measure the RES_IDEAL ≥ RES_HOT and RES_HOT ≥
RES_UR thresholds by connecting the THA pin to V
measuring the voltage resultant on the THB pin.
The SafetySignal decoder block uses a voltage divider
network between V
nal range thresholds. Since the THA and THB inputs are
sequentially connected to V
immunity during SafetySignal measurement.
When AC power is not available the SafetySignal block
supports the following low power operating features:
1. The SafetySignal is sampled every 250ms or less,
2. A full SafetySignal status is sampled every 30s or less,
18
instead of 32ms.
instead of every 32ms.
THB
resistor value is used to measure the RES_OR
DD
and GND to determine SafetySig-
DD
DD
and measuring the voltage
, this provides V
THA
resistor value is used
DD
DD
noise
and
The SafetySignal impedance is interpreted according to
Table 4.
Table 4. SafetySignal State Ranges
SafetySignal
RESISTANCE
0Ω to 500Ω
500Ω to 3kΩ
3kΩ to 30kΩ
30kΩ to 100kΩ
Above 100kΩ
Note: The underrange detection scheme is a very important feature of the
LTC4100. The R
well above the 0.047 • V
pull-up. A system using a 10k pull-up would not be able to resolve the
important underrange to hot transition point with a modest 100mV of
ground offset between battery and SafetySignal detection circuitry. Such
offsets are anticipated when charging at normal current levels.
The required values for R
Table 5.
Table 5. SafetySignal External Resistor Values
C
and GND. C
immunity from transients in the application. C
exceed 1nF if the LTC4100 is to properly sense the value
of R
SS
SafetySignal
represents the capacitance between the SafetySignal
EXTERNAL RESISTOR
R
R
THA
SS
THA
THB
.
/R
may be added to provide additional noise
SafetySignal
CHARGE STATUS BITS
RES_UR
RES_HOT
BATTERY_PRESENT
RES_HOT
BATTERY_PRESENT
BATTERY_PRESENT
RES_COLD
BATTERY_PRESENT
RES_OR RES_COLD
DD
(140mV) threshold of a system using a 10k
divider trip point of 0.333 • V
THA
and R
VALUE (Ω)
54.9k ±1%
THB
1130 ±1%
DESCRIPTION
Underrange
Hot
Ideal
Cold
Overrange
are shown in
DD
SS
(1V) is
cannot
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