Q24T30020 DC-DC Converter Data Sheet
18-36 VDC Input; 2.0 VDC @ 30A Output
VIN
Start-up Information (using negative ON/OFF)
Scenario #1: Initial Start-up From Bulk Supply
ON/OFF function enabled, converter started via application of VIN.
See Figure 7.
ON/OFF
STATE
OFF
Time
t0
Comments
ON/OFF pin is ON; system front end power is toggled
on, VIN to converter begins to rise.
t1
t2
t3
VIN crosses Under-Voltage Lockout protection circuit
threshold; converter enabled.
Converter begins to respond to turn-on command (con-
verter turn-on delay).
ON
VOUT
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is typically
2.5 ms.
t
t
t
t0
t1 t2
t3
Fig. 7: Start-up scenario #1.
VIN
Scenario #2: Initial Start-up Using ON/OFF Pin
With VIN previously powered, converter started via ON/OFF pin.
See Figure 8.
Time
t0
t1
Comments
VINPUT at nominal value.
Arbitrary time when ON/OFF pin is enabled (converter
enabled).
ON/OFF
STATE
OFF
t2
t3
End of converter turn-on delay.
Converter VOUT reaches 100% of nominal value.
For this example, the total converter start-up time (t3- t1) is typically
2.5 ms.
ON
VOUT
Scenario #3: Turn-off and Restart Using ON/OFF Pin
With VIN previously powered, converter is disabled and then en-
abled via ON/OFF pin. See Figure 9.
t0
t1 t2
t3
Time
Comments
t0
t1
VIN and VOUT are at nominal values; ON/OFF pin ON.
ON/OFF pin arbitrarily disabled; converter output falls
to zero; turn-on inhibit delay period (100 ms typical) is
initiated, and ON/OFF pin action is internally inhibited.
ON/OFF pin is externally re-enabled.
Fig. 8: Start-up scenario #2.
VIN
t2
If (t2- t1) ≤ 100 ms, external action of ON/OFF pin
is locked out by start-up inhibit timer.
If (t2- t1) > 100 ms, ON/OFF pin action is internally
enabled.
100 ms
ON/OFF
STATE
OFF
ON
t3
Turn-on inhibit delay period ends. If ON/OFF pin is ON,
converter begins turn-on; if off, converter awaits
ON/OFF pin ON signal; see Figure 8.
t4
t5
End of converter turn-on delay.
Converter VOUT reaches 100% of nominal value.
VOUT
For the condition, (t2- t1) ≤ 100 ms, the total converter start-up
time (t5- t2) is typically 102.5 ms. For (t2- t1) > 100 ms, start-up will
be typically 2.5 ms after release of ON/OFF pin.
t0
t1
t2
t3 t4
t5
Fig. 9: Start-up scenario #3.
JUN 01, 2003 revised to NOV 22, 2006
Page 9 of 14
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