参数资料
型号: LT1240-7DZFB1
厂商: POWER-ONE INC
元件分类: 电源模块
英文描述: 1-OUTPUT 500 W AC-DC REG PWR SUPPLY MODULE
封装: CASE T01, MODULE
文件页数: 9/33页
文件大小: 864K
代理商: LT1240-7DZFB1
Cassette Style
AC-DC Converters
T Series
Edition 5/5.2000
17/33
Power down output signal characteristics
The power down output D is an open collector transistor
referenced to Vo–, protected by a 62 V Zener diode, and is
well suited to driving an external relay.
Under normal operating conditions (
Uo
> U
t) the power
down output D has low impedance. If the output voltage
drops below the power down threshold level, the signal out-
put becomes high impedance.
Table 14: Characteristics of Power Down functions
Characteristics
Conditions
min typ max
Unit
ID
Output
TC min...TC max
50 1
mA
sink current
Usat U saturation
ID = 50 mA
0.2
V
Uz
Zener voltage
62
Pz
Z-diode
PLOSS
TC = 95 °C
500
mW
1 To be limited to 50 mA by the external circuitry.
Vo+
D
30
Vo–
D set
32
T 1000
Rext
06053
12
22
Fig. 29
Power Down
– External adjustment of threshold level Ut
– Signal electrically isolated by an external relay
Fig. 30
Remote indication of Power Down by LED
red LED
Vo+
D
Vo–
LED is "ON"
in case of
power down
R
T 1000
06054
12
30
22
Fig. 31
Remote indication of the output voltage status by CMOS/
TTL interface for e.g. Save Data
Vo+
D
Vo–
T 1000
+5 V
CMOS, TTL
R
06055
12
30
22
The threshold level is adjusted to a DC output voltage.
When in operation a sinusoidal low frequency output ripple
is superimposed on the DC output voltage. It can be esti-
mated with
Uov = Io/(2
π f C
o) where C o is the internal
capacitance of the output of the unit.
Table 13: Resistor values (Rext) for given Power Down
threshold value Ut for LT 1740 (typical values)
Characteristics
Conditions
Ut
Unit
Ut
Power Down
69 k
to Vo+
34.4
V
threshold level set by
106 k
to Vo+
36.4
Rext
254 k
to Vo+
39.5
left open
42.5
309 k
to Vo–
45.5
154 k
to Vo–
48.5
102 k
to Vo–
51.6
Upper threshold level
The upper threshold level of the Power down function is
given.
The rectifier units T xx01/02 have a relatively small hyster-
esis of 1 V to prevent oscillation of the signal.
The battery charger units T xx40 have a large hysteresis.
The upper level is set at 2.05 V/cell.
To avoid deep discharge of the battery which would de-
crease the life expectancy, its load should be disconnected
from the battery at the low level of the Power down signal.
The battery voltage will then recover slowly up to its chemi-
cal equilibrium, about 2 V/cell. The load may not be con-
nected again to the battery until the T unit is operating and
charging it. Then the output voltage will be higher than
2.05 V/cell
High level of Power down signal
T 1240:
24.6 V
±0.3 V
T 1740:
49.2 V
±0.5 V
T 1840:
36.9 V
±0.4 V
U Bat
U float
Battery
recovery
Battery
low
Mains failure
Return of mains
Hysteresis
Power Down
Load switch ON
Load switch OFF
t
U t
Z
t
high
low
Power down signal
2.05 V/cell
2.0 V/cell
06052
Fig. 28
Hysteresis of power down signal for battery charger types
with corresponding level of power down signal
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