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Demonstration System EPC9126xx
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OTHER FEATURES
Narrow pulse generator:
Many signal generators cannot produce an accurate, short pulse.
The EPC9126xx includes a function to obtain narrow output pulses, following
a method given in Section 8.2.2.2 of the Texas Instruments LMG1020 data
sheet. This is controlled through DIP switch S1. For normal operation, position
6 should be ON, and the positions 1 through 5 should be OFF. In this case, the
input pulse to J5 will be passed to the gate drive unmodified.
To operation the narrow pulse generator, move position 6 to OFF. The pulse
input to J5 is now a trigger pulse and must be set to at least 60 ns, with at
least 300ns off time between pulses. The pulse width can now be adjusted
via S1 switch positions 1 through 5. For best results, keep position 1 in the
OFF state. For very narrow pulses, the position 1 switch may be turned ON,
but reliable operation cannot be expected. Approximate pulse width values
are summarized in Table 3. Since these values are approximate, user must
verify as necessary.
Switch setting (Pos 1 = OFF)
Pulse
width
(ns)
6
5
4
3
2
1
0
0
0
0
0
0
60.4
0
1
0
0
0
0
38.1
0
0
1
0
0
0
18.5
0
1
1
0
0
0
11.5
0
0
0
1
0
0
9.3
0
1
0
1
0
0
6.6
0
0
1
1
0
0
5.5
0
1
1
1
0
0
5.1
0
0
0
0
1
0
4.9
0
1
0
0
1
0
3.4
0
0
1
0
1
0
2.9
0
1
1
0
1
0
2.4
0
0
0
1
1
0
2.1
0
1
0
1
1
0
1.9
0
0
1
1
1
0
1.7
0
1
1
1
1
0
1.2
Switch setting (Pos 1 = ON)
Pulse
width
(ns)
6
5
4
3
2
1
0
0
0
0
0
1
1.6
0
1
0
0
0
1
1.46
0
0
1
0
0
1
1.32
0
1
1
0
0
1
1.17
0
0
0
1
0
1
0.96
0
1
0
1
0
1
0.65
0
0
1
1
0
1
0.45
0
1
1
1
0
1
0.32
0
0
0
0
1
1
0.3
0
1
0
0
1
1
0
0
0
1
0
1
1
0
0
1
1
0
1
1
0
0
0
0
1
1
1
0
0
1
0
1
1
1
0
0
0
1
1
1
1
0
0
1
1
1
1
1
0
Table 3: Narrow pulse generator switch settings with S1 Pos 6 = OFF. (a): POS 1 = OFF (recommended). (b) POS 1 = ON (not recommended for reliable operation).
(a)
(b)
Modifications:
While diodes D1 and D2 can provide some protection to FET Q1 and
laser D3, they have parasitic inductance and capacitance that can reduce
performance at the very fastest speeds. Hence, they are not populated,
and it is left to the user to determine whether they are necessary for a
particular application.
The value of the shunt resistors can be increased up to a point to improve
the discharge cap current sense accuracy. Note that accurate measure-
ment of current while inserting extremely low inductance into the power
loop is extremely challenging, and many factors must be considered.
For the lowest possible inductance, the resistors can be replaced with
copper foil if no sensing is needed.
The value of the energy storage cap {C11, C12, C13, C14, C15} can be
modified as desired, as well as the recharge resistor {R2, R3, R5, R6}.
In the extreme case, the resistor may be reduced to 0 Ω for cases where a
capacitive discharge pulse is not desired.