LTC4100EGPBF LINER [Linear Technology], LTC4100EGPBF Datasheet - Page 10

• Manufacturer Part Number: LTC4100EGPBF
• Description: Smart Battery Charger Controller
• Manufacturer: LINER [Linear Technology]

TEST CIRCUIT
LTC4100
OPERATION
Overview (Refer to Block Diagram)
The LTC4100 is composed of a battery charger section, a
charger controller, a 10-bit DAC to control charger current,
an 11-bit DAC to control charger voltage, a SafetySignal
decoder, limit decoder and an SMBus controller block. If
no battery is present, the SafetySignal decoder indicates
a RES_OR condition and charging is disabled by the
charger controller (CHGEN = Low). Charging will also be
disabled if DCDIV is low, or the SafetySignal is decoded
as RES_HOT. If a battery is inserted and AC power is
connected, the battery will be charged with an 80mA
“wake-up” current. The wake-up current is discontinued
after t
or RES_C0LD, and the battery or host doesn’t transmit
charging commands.
The SMBus interface and control block receives Charg-
ingCurrent() and ChargingVoltage() commands via the
SMBus. If ChargingCurrent() and ChargingVoltage()
command pairs are received within a t
values are stored in the current and voltage DACs and the
10
TIMEOUT
CSP
if the SafetySignal is decoded as RES_UR
21
22
BAT V
–
+
SET
18
1.19V
LT1055
TIMEOUT
+
–
V
EA
DAC
–
+
interval, the
I
TH
LTC4100
19
4100 TC01
0.6V
charger controller asserts the CHGEN line if the decoded
SafetySignal value will allow charging to commence. Charg-
ingCurrent() and ChargingVoltage() values are compared
against limits programmed by the limit decoder block; if
the commands exceed the programmed limits these limits
are substituted and overrange fl ags are set.
The charger controller will assert SMBALERT when-
ever a status change is detected, namely: AC_PRESENT,
BATTERY_PRESENT, ALARM_INHIBITED, or V
fail. The host may query the charger, via the SMBus, to
obtain ChargerStatus() information. SMBALERT will be
deasserted upon a successful read of ChargerStatus() or
a successful Alert Response Address (ARA) request.
Battery Charger Controller
The LTC4100 charger controller uses a constant off-time,
current mode step-down architecture. During normal
operation, the top MOSFET is turned on each cycle when
the oscillator sets the SR latch and turned off when
the main current comparator I
V
TOL
=
DCIN
CLN CLP
FOR V
V
BAT
V
=
VDAC
–
=
VDAC
V
21
VDAC
V
=
=
20
17 57 0 44 0
•
100
V
.
V x
CMP
(
resets the SR latch.
A
)
DD
power-
4100fb