Datasheet

LM13700
SNOSBW2E –NOVEMBER 1999–REVISED MARCH 2013 www.ti.com
Figure 43. Schmitt Trigger
Figure 44 shows a Tachometer or Frequency-to-Voltage converter. Whenever A1 is toggled by a positive-going
input, an amount of charge equal to (V
H
–V
L
) C
t
is sourced into C
f
and R
t
. This once per cycle charge is then
balanced by the current of V
O
/R
t
. The maximum F
IN
is limited by the amount of time required to charge C
t
from
V
L
to V
H
with a current of I
B
, where V
L
and V
H
represent the maximum low and maximum high output voltage
swing of the LM13700. D1 is added to provide a discharge path for C
t
when A1 switches low.
The Peak Detector of Figure 45 uses A2 to turn on A1 whenever V
IN
becomes more positive than V
O
. A1 then
charges storage capacitor C to hold V
O
equal to V
IN
PK. Pulling the output of A2 low through D1 serves to turn
off A1 so that V
O
remains constant.
Figure 44. Tachometer
Figure 45. Peak Detector and Hold Circuit
20 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated
Product Folder Links: LM13700