LTC4007(RevA) データシートの表示（PDF） - Linear Technology
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LTC4007 Datasheet PDF : 24 Pages
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LTC4007
U
OPERATIO
Table 1. Truth Table For Indicator States
MODE
Shut down by low adapter voltage
Charging a low bat
Normal charging
Input current limited charging
Charger paused due to thermistor out of range
Shut down by SHDN pin
Terminated by low-battery fault (Note 1)
DCIN
<BAT
>BAT
>BAT
>BAT
>BAT
X
>BAT
SHDN
LOW
LOW
LOW
LOW
LOW
HIGH
LOW
ACP**
LOW
HIGH
HIGH
HIGH
HIGH
X
HIGH
LOBAT
LOW
LOW
HIGH
HIGH
X
X
LOW
FLAG** FAULT**
HIGH HIGH
HIGH* HIGH*
HIGH HIGH*
HIGH* HIGH*
X
LOW
(from
NTC)
HIGH HIGH
HIGH* LOW
ICL
LOW
HIGH*
HIGH*
LOW
HIGH
LOW
LOW
TIMER
STATE
Reset
Running
Running
Running
Paused
Reset
>T/4
Timer is reset when FLAG goes low, then
terminates after 1/4 T
Terminated by expired timer
>BAT LOW HIGH HIGH LOW HIGH LOW
>T/4
after
FLAG =
LOW
>BAT LOW HIGH HIGH HIGH HIGH LOW
>T
Timer defeated
X
X
X
X
X
X
X
Shut down by undervoltage lockout
>BAT LOW
+ <UVL
HIGH
HIGH
HIGH HIGH* LOW
*Most probable condition X = Don’t care, ** Open-drain output HIGH = OPEN with pull-up
Note 1: If a depleted battery is inserted while the charger is in this state, the
charger must be reset to initiate charging.
X
Reset
CHG**
HIGH
LOW
LOW
LOW
LOW
HIGH
HIGH
(Faulted)
HIGH
(Waiting
for Restart)
HIGH
(Waiting
for Restart
Forced LOW
HIGH*
a low forward voltage drop from drain to source. If the
voltage between DCIN and CLN drops to less than 25mV,
the input FET is turned off slowly. If the voltage between
DCIN and CLN is ever less than – 25mV, then the input FET
is turned off in less than 10µs to prevent significant
reverse current from flowing in the input FET. In this
condition, the ACP pin is driven low and the charger is
disabled.
Battery Charger Controller
The LTC4007 charger controller uses a constant off-time,
current mode step-down architecture. During normal op-
eration, the top MOSFET is turned on each cycle when the
oscillator sets the SR latch and turned off when the main
current comparator ICMP resets the SR latch. While the top
MOSFET is off, the bottom MOSFET is turned on until
either the inductor current trips the current comparator
IREV or the beginning of the next cycle. The oscillator uses
the equation:
tOFF
=
VDCIN –
VDCIN •
VBAT
fOSC
to set the bottom MOSFET on time. The result is a nearly
constant switching frequency over a wide input/output
voltage range. This activity is diagrammed in Figure 1.
OFF
TGATE
ON
ON
BGATE
OFF
INDUCTOR
CURRENT
tOFF
TRIP POINT SET BY ITH VOLTAGE
Figure 1
4006 F01
4007fa
10
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