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參數(shù)資料
| 型號： | LM26 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Adapter Interface Circuit |
| 中文描述： | 適配器接口電路 |
| 文件頁數(shù)： | 4/6頁 |
| 文件大?。?/td> | 130K |
| 代理商： | LM26 |
Electrical Characteristics
(Continued)
Note 5:
Adapter Enable input is used to change the state of Disconnect, Direction Sense input is used to change the state of Backfeed.
a.
Fall time is measured as the time it takes Backfeed or Disconnect voltage to go from a high level (approx. V
ADAPTER
0.5V) to (V
ADAPTER
4V) after the signal
is initiated at Adapter Enable or Direction Sense.
b.
Rise time is measured as the time it takes Backfeed or Disconnect voltage to go from a low level (approx. 0.5V) to (V
ADAPTER
2V) after the signal is initiated
at Adapter Enable or Direction Sense.
Typical Application
10130903
Notes
1.
R
value should be selected to guarantee that a
programmed over current will cause a voltage drop
across R
of approx. 135mV. If a higher value of
R
has to be selected then R1/R3 resistor divider
should be used to scale the voltage drop down.
Internal and external circuits associated with Direction
Sense and Backfeed FET pins allow to emulate a Schot-
tky diode functionality with much lower forward voltage
drop and, therefore, with much lower power dissipation.
R2/R4 resistor divider programs the backfeed current
protection threshold. The backfeed FET Q1 turns off
when the backfeed current pulse level causes more than
9 mV (typical value) voltage drop between V
adapter
pin
and Direction Sense pin.
Voltage difference (V
- V
) must
be higher than 20mV to reliably isolate the adapter in
case of leakage.
R5 and R6 prevent the FETs from turning on unless
driven by LM2601.
2.
3.
4.
5.
C
value can be calculated from the following for-
mula:
C
DELAY
(nF) = T
DELAY
(μs)/90 at 25C
T
temperature coefficient equals 4000ppm/C. See
also the Typical Delay Time vs. Temperature graph.
Pin Master Power Source (MPS) should be connected to
System Management Controller’s (SMC) and battery
packs’ GPIOs. When SMC detects a powered AC
adapter via active signals at Charger Present or Adapter
Present outputs, it asserts Adapter Enable signal and
isolates the battery pack(s). Adapter Enable signal turns
the Disconnect FET on. When the AC adapter is un-
plugged or powered off, SMC enables one of the system
battery packs. The battery packs’ embedded controller
starts driving the logic MPS signal high that turns the
Disconnect FET off.
6.
7.
L
www.national.com
4
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