19
Figure 39. Minimum LED Skew for Zero Dead Time.
Figure 38. Under Voltage Lock Out.
Under Voltage Lockout Feature. (Discussion applies to
ACPL-3130, ACPL-J313, and ACNW3130)
The ACPL-3130 contains an under voltage lockout (UVLO)
feature that is designed to protect the IGBT under fault
conditions which cause the ACPL-3130 supply voltage
(equivalent to the fully-charged IGBT gate voltage) to
drop below a level necessary to keep the IGBT in a low
resistance state. When the ACPL-3130 output is in the high
state and the supply voltage drops below the ACPL-3130
VUVLO– threshold (9.5 < VUVLO– < 12.0) the optocoupler
output will go into the low state with a typical delay, UVLO
Turn O Delay, of 0.6 µs.
When the ACPL-3130 output is in the low state and the
supply voltage rises above the ACPL-3130 VUVLO+ threshold
(11.0 < VUVLO+ < 13.5) the optocoupler output will go into
the high state (assumes LED is “ON”) with a typical delay,
UVLO Turn On Delay of 0.8 µs.
Dead Time and Propagation Delay Specications. (Discus-
sion applies to ACPL-3130, ACPL-J313, and ACNW3130)
The ACPL-3130 includes a Propagation Delay Dierence
(PDD) specication intended to help designers minimize
“dead time” in their power inverter designs. Dead time
is the time period during which both the high and low
side power transistors (Q1 and Q2 in Figure 29) are o.
Any overlap in Q1 and Q2 conduction will result in large
currents owing through the power devices between the
high and low voltage motor rails.
Figure 37. Recommended LED Drive Circuit for Ultra-High CMR.
To minimize dead time in a given design, the turn on of
LED2 should be delayed (relative to the turn o of LED1)
so that under worst-case conditions, transistor Q1 has just
turned o when transistor Q2 turns on, as shown in Figure
35. The amount of delay necessary to achieve this condition
is equal to the maximum value of the propagation delay
dierence specication, PDDMAX, which is specied to be
350 ns over the operating temperature range of -40°C to
100°C.
Delaying the LED signal by the maximum propagation
delay dierence ensures that the minimum dead time is
zero, but it does not tell a designer what the maximum
dead time will be. The maximum dead time is equivalent
to the dierence between the maximum and minimum
propagation delay dierence specications as shown in
Figure 40. The maximum dead time for the ACPL-3130 is
700 ns (= 350 ns - (-350 ns)) over an operating temperature
range of - 40°C to 100°C.
Note that the propagation delays used to calculate PDD
and dead time are taken at equal temperatures and test
conditions since the optocouplers under consideration
are typically mounted in close proximity to each other and
are switching identical IGBTs.
1
3
2
4
8
6
7
5
C
LEDP
C
LEDN
SHIELD
+5 V
V
O
- OUTPUT VOLTAGE - V
0
0
(V
CC
- V
EE
) - SUPPLY VOLTAGE - V
10
5
14
10 15
2
20
6
8
4
12
(12.3, 10.8)
(10.7, 9.2)
(10.7, 0.1) (12.3, 0.1)
tPHL MAX
tPLH MIN
PDD* MAX = (t PHL - tPLH )MAX = t PHL MAX - tPLH MIN
*PDD = PROPAGATION DELAY DIFFERENCE
NOTE: FOR PDD CALCULATIONS THE PROPAGATION DELAYS
ARE TAKEN AT THE SAME TEMPERATURE AND TEST CONDITIONS.
VOUT1
ILED2
VOUT2
ILED1
Q1 ON
Q2 OFF
Q1 OFF
Q2 ON