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LTC6993IS6-4#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LTC6993-1/LTC6993-2
LTC6993-3/LTC6993-4
13
69931234fc
For more information www.linear.com/LTC6993-1
operaTion
Table 1. DIVCODE Programming
DIVCODE POL N
DIV
Recommended t
OUT
R1 (k) R2 (k) V
DIV
/V
+
0 0 1 1µs to 16µs Open Short ≤ 0.03125 ±0.015
1 0 8 8µs to 128µs 976 102 0.09375 ±0.015
2 0 64 64µs to 1.024ms 976 182 0.15625 ±0.015
3 0 512 512µs to 8.192ms 1000 280 0.21875 ±0.015
4 0 4,096 4.096ms to 65.54ms 1000 392 0.28125 ±0.015
5 0 32,768 32.77ms to 524.3ms 1000 523 0.34375 ±0.015
6 0 262,144 262.1ms to 4.194sec 1000 681 0.40625 ±0.015
7 0 2,097,152 2.097sec to 33.55sec 1000 887 0.46875 ±0.015
8 1 2,097,152 2.097sec to 33.55sec 887 1000 0.53125 ±0.015
9 1 262,144 262.1ms to 4.194sec 681 1000 0.59375 ±0.015
10 1 32,768 32.77ms to 524.3ms 523 1000 0.65625 ±0.015
11 1 4,096 4.096ms to 65.54ms 392 1000 0.71875 ±0.015
12 1 512 512µs to 8.192ms 280 1000 0.78125 ±0.015
13 1 64 64µs to 1.024ms 182 976 0.84375 ±0.015
14 1 8 8µs to 128µs 102 976 0.90625 ±0.015
15 1 1 1µs to 16µs Short Open ≥ 0.96875 ±0.015
0.5• V
+
t
OUT
(ms)
69931234 F02
1000
10000
100
10
1
0.001
0.1
0.01
INCREASING V
DIV
V
+
0V
POL BIT = 0
0
1
2
3
4
5
6
7 8
9
10
11
12
13
14
15
POL BIT = 1
Figure 2. Pulse Width Range and POL Bit vs DIVCODE
LTC6993-1/LTC6993-2
LTC6993-3/LTC6993-4
14
69931234fc
For more information www.linear.com/LTC6993-1
operaTion
Monostable Multivibrator (One Shot)
The LTC6993 is a monostable multivibrator. A trigger
signal on the TRIG input will force the output to the active
(unstable) state for a programmable duration. This type
of circuit is commonly referred to as a one-shot pulse
generator.
Figures 3 details the basic operation. A rising edge on
the TRIG pin initiates the output pulse. The pulse width
(t
OUT
) is determined by the N
DIV
setting and by the resis-
tor (R
SET
) connected to the SET pin. Subsequent rising
edges on TRIG have no affect until the completion of the
one shot and for a short rearming time (t
ARM
) thereafter.
To ensure proper operation, positive and negative TRIG
pulses should be at least t
WIDTH
wide.
The LTC6993-2 and LTC6993-4 allow the output pulse to
be “retriggered”. As shown in Figure 4, the output pulse
will stay high until t
OUT
after the last rising-edge on TRIG.
Successive trigger signals can extend the pulse width in-
definitely. Consecutive trigger signals must be separated
by t
RETRIG
to be recognized.
Negative Trigger Versions
In addition to the retrigger option, the LTC6993 family also
includes negative input (falling-edge) versions. These four
combinations are detailed in Table 2.
Table 2. Retrigger and Input Polarity Options
DEVICE INPUT POLARITY RETRIGGER
LTC6993-1 Rising-Edge No
LTC6993-2 Rising-Edge Yes
LTC6993-3 Falling-Edge No
LTC6993-4 Falling-Edge Yes
Output Polarity (POL Bit)
Each variety of LTC6993 also offers the ability to invert
the output, producing negative pulses. This option is
programmed, along with N
DIV
, by the choice of DIVCODE.
(The previous section describes how to program DIVCODE
using the DIV pin).
Figure 3. Non-Retriggering Timing Diagram (LTC6993-1, POL = 0)
Figure 4. Retriggering Timing Diagram (LTC6993-2, POL = 0)
t
PD
t
WIDTH
t
RETRIG
TRIG
OUT
t
OUT
t
PD
t
PD
t
PD
t
OUT
t
OUT
69931234 F04
t
PD
TRIG
OUT
t
PD
t
ARM
t
WIDTH
t
OUT
t
OUT
t
OUT
69931234 F03
LTC6993-1/LTC6993-2
LTC6993-3/LTC6993-4
15
69931234fc
For more information www.linear.com/LTC6993-1
operaTion
Changing DIVCODE After Start-Up
Following start-up, the A/D converter will continue
monitoring V
DIV
for changes. Changes to DIVCODE will
be recognized slowly, as the LTC6993 places a priority on
eliminating any “wandering” in the DIVCODE. The typical
delay depends on the difference between the old and
new DIVCODE settings and is proportional to the master
oscillator period.
t
DIVCODE
= 16 • (∆DIVCODE + 6) • t
MASTER
A change in DIVCODE will not be recognized until it is
stable, and will not pass through intermediate codes. A
digital filter is used to guarantee the DIVCODE has settled
to a new value before making changes to the output. How
-
ever, if the output pulse is active during the transition, the
pulse width can take on a value between the two settings.
Start-Up Time
When power is first applied, the power
-on reset (POR)
circuit will initiate the start-up time, t
START
. The OUT pin
is held low during this time. The typical value for t
START
ranges from 0.5ms to 8ms depending on the master oscil-
lator frequency (independent of N
DIV
):
t
START(TYP)
= 500 • t
MASTER
During start-up, the DIV pin A/D converter must deter-
mine the correct DIVCODE before an output pulse can be
generated.
The
start-up time may increase if the supply
or DIV pin voltages are not stable. For this reason, it is
recommended to minimize the capacitance on the DIV
pin so it will properly track V
+
. Less than 100pF will not
extend the start-up time.
The DIVCODE setting is recognized at the end of the startup
up. If POL = 1, the output will transition high. Otherwise
(if POL = 0) OUT simply remains low. At this point, the
LTC6993 is ready to respond to rising/falling edges on
the TRIG input.
Figure 5a. DIVCODE Change from 0 to 2
Figure 5b. DIVCODE Change from 2 to 0
Figure 6. Start-Up Timing Diagram
DIV
500mV/DIV
TRIG
2V/DIV
OUT
2V/DIV
LTC6993-1
V
+
= 3.3V
R
SET
= 200k
200µs/DIV
69931234 F05a
512µs
256µs
4µs
DIV
500mV/DIV
TRIG
2V/DIV
OUT
2V/DIV
LTC6993-1
V
+
= 3.3V
R
SET
= 200k
200µs/DIV
69931234 F05b
512µs
256µs
4µs
TRIG
V
+
OUT
t
START
(TRIG IGNORED)
t
OUT
POL = 1
69931234 F06
POL = 0
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28

LTC6993IS6-4#TRPBF

Mfr. #:
Buy LTC6993IS6-4#TRPBF
Manufacturer:
Analog Devices Inc.
Description:
Monostable Multivibrator One Shot with Falling Edge Trigger, Retriggerable
Lifecycle:
New from this manufacturer.
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