ic-wj iC-Haus, ic-wj Datasheet - Page 8

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ic-wj

Manufacturer Part Number
ic-wj
Description
Laser Diode Driver
Manufacturer
iC-Haus
Datasheet

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Example
CI = 470 nF, RSET = 10 k : T
Figure 6 shows a detailed view of the start of laser op-
eration; Figure 7 shows the shut-down behavior. The
decline in the voltage at CI and the absence of the
laser pulses are signs that the undervoltage detector
is active.
Watchdog
In order for the watchdog to function correctly, the input
IN must be activated with a CMOS output (e.g. with an
HCMOS gate: see Figure 1).
The watchdog ensures that the capacitor CI is dis-
charged during protracted pulse pulses at IN. During
the pulse pauses the potential at CI increases by
(Figure 3):
The discharge of capacitor CI by the watchdog protects
the laser diode from being destroyed by an excessive
turn-on current during the next pulse.
iC-WJ, iC-WJZ
LASER DIODE DRIVER
2.55 V
2.45 V
Figure 6: Turn-on behavior, detailed view f(IN) =
5.0 V
3.0 V
Figure 7: Turn-off behavior, f(IN) = 100 kHz (1:1), CI
0 V
0 V
0 A
0 A
100 kHz (1:1), CI = 470 nF, RSET = 10 k
= 470 nF, RSET = 10 k
VCC
V =
I(ISET ) t
I(KLD)
V(CI)
CI
on
V(CI)
= 9.6 ms
wlo
I(KLD)
Time
Time
V
The capacitor CWD should be dimensioned such that
the response time t
than the pulse pause t
sult, the watchdog is just short of being activated.
For response times t
with t
No. 407, 408.
Figure 8 shows the signals during normal operation,
without the watchdog being activated. The potential at
CWD rises during pulse pauses but does not reach the
watchdog activation threshold.
Figure 9 shows the watchdog behavior when the in-
put frequency is reduced from 100 kHz to 10 kHz. The
pulse pauses are longer than the watchdog’s response
300 uA
Figure 8: Watchdog, CWD open, f(IN) = 100 kHz
300 uA
Figure 9: Watchdog, CWD open, f(IN) = 100 kHz
5.0 V
5.0 V
3.0 V
2.0 V
5.0 V
0 A
0 V
0 V
0 A
0 V
5 V
0 V
3 V
2 V
pmin
V(CWD)
(1:1), CI = 470 nF, RSET = 10 k
10 kHz (1:1), CI = 470 nF, RSET = 10 k
and K
V(CWD)
wd
CWD =
p
I(AMD)
p
of the watchdog is slightly longer
V(IN)
V(CI)
longer than t
from Electrical Characteristics
wlo
V(IN)
of the input signal. As a re-
I(AMD)
t
p
K
V(CI)
wd
t
pmin
pmin
Rev C1, Page 8/12
applies:
Time
Time

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