H Series Data Sheet
70 Watt AC-DC Converters
BCD20019 Rev AA
Page 17 of 21
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0
1
0.95
0
Vi [V DC]
0
t
tlow min4
thigh min
th1
Vti + Vhi
Vti
Input voltage failure
Switch-on cycle
Input voltage sag
Switch-on cycle and subsequent
input voltage failure
VD high
VD low
VD
0
JFET
NPN
t
Vo1
Vo1 nom
VD high
VD low
VD
tlow min4
th1
0
VD high
VD low
VD
0
JFET
NPN
Vo1
VD high
VD low
VD
tlow min4
Vto
3
Output voltage failure
0
ID high
ID low
ID
t
0
ID high
ID low
ID
t
3
2
33
Vo1 nom
Vto +Vho
Input voltage monitoring
Output voltage monitoring
11008a
Fig. 21
Relationship between Vi, Vo1, VD, ID, and Vo1/Vo nom
versus time.
1 th = hold-up time.
2 With output voltage monitoring the hold-up time t h = 0
3 The D signal remains high, if the D output is connected
to an external source.
4 t low min = 40 – 200 ms, typically 80 ms
V ACFAIL Signal (VME)
Available for converters with Vo1 = 5.1 V. This option defines an
undervoltage monitoring circuit for the input or the input and
main output voltage equivalent to option D and generates the
ACFAIL signal (V signal), which conforms to the VME
standard. The low state level of the ACFAIL signal is specified
at a sink current of IV = 48 mA to VV – 0.6 V (open-collector
output). The pull-up resistor feeding the open-collector output
should be placed on the VME backplane.
After the ACFAIL signal has gone low, the VME standard
requires a hold-up time th of at least 4 ms before the 5.1 V
output drops to 4.875 V, when the 5.1 V output is fully loaded.
This hold-up time t h is provided by the internal input