TC9402 TELCOM [TelCom Semiconductor, Inc], TC9402 Datasheet - Page 6

• Manufacturer Part Number: TC9402
• Description: VOLTAGE-TO-FREQUENCY/FREQUENCY-TO-VOLTAGE CONVERTERS
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

TC9400
TC9401
TC9402
3-292
V/F converter always operates properly when power is first
applied. In the event that, during power-on, the Op Amp
output is below the threshold and C
a positive voltage step will not occur. The op-amp output will
continue to decrease until it crosses the –3.0V threshold of
the "self-start" comparator. When this happens, an internal
resistor is connected to the op-amp input, which forces the
output to go positive until the TC9400 is in its normal
operating mode.
low input bias and offset currents with very low power
dissipation. The open-drain N-channel output FETs provide
high voltage and high current sink capability.
VOLTAGE-TO-TIME MEASUREMENTS
main as well as the frequency domain. Some microcom-
puters, for example, have extensive timing capability but
limited counter capability. Also, the response time of a time
domain measurement is only the period between two out-
put pulses, while the frequency measurement must accu-
mulate pulses during the entire counter timebase period.
TC9400's Pulse Freq Out output or from the Freq/2 output.
The Freq/2 output changes state on the rising edge of
Pulse Freq Out, so Freq/2 is a symmetrical square wave at
one half the pulse output frequency. Timing measurements
can therefore be made between successive Pulse Freq
Out pulses, or while Freq/2 is high (or low).
The TC9400 contains a "self-start" circuit to ensure the
The TC9400 utilizes low power CMOS processing for
The TC9400 output can be measured in the time do-
Time measurements can be made from either the
f OUT /2
AMP
OUT
f OUT
NOTES: 1. To adjust f MIN , set V IN = 10mV and adjust the 50k offset for 10Hz output.
2. To adjust f MAX , set V IN = 10V and adjust R IN or V REF for 10 kHz output.
3. To increase f OUT MAX to 100kHz, change C REF to 2pF and C INT to 75pF.
4. For high-performance applications, use high-stability components for R IN , C REF , V REF (metal film
resistors and glass capacitors). Also, separate output ground (pin 9) from input ground (pin 6).
1/f
REF
3 µsec
TYP
is already charged,
Figure 2 . Output Waveforms
FREQUENCY-TO-VOLTAGE CONVERTERS
PIN FUNCTIONS
Threshold Detector Input
output (pin 12) and triggers a 3 sec pulse when the input
voltage passes through its threshold. In the F/V mode, the
input frequency is applied to this input.
tween the power supplies, or (V
TC9400's charge balancing V/F technique is not dependent
on a precision comparator threshold, because the threshold
only sets the lower limit of the op-amp output. The op-amp's
peak-to-peak output swing, which determines the frequency,
is only influenced by external capacitors and by V
Pulse Freq Out
provides a pulse waveform whose frequency is proportional
to the input voltage. This output requires a pull-up resistor
and interfaces directly with MOS, CMOS, and TTL logic.
Freq/2 Out
provides a square wave one-half the frequency of the pulse
frequency output. The Freq/2 output will change state on the
rising edge of Pulse Freq Out. This output requires a pull-
up resistor and interfaces directly with MOS, CMOS, and
TTL logic.
In the V/F mode, this input is connected to the amplifier
The nominal threshold of the detector is halfway be-
This output is an open-drain N-channel FET which
This output is an open-drain N-channel FET which
VOLTAGE-TO-FREQUENCY/
TELCOM SEMICONDUCTOR, INC.
DD
+ V
SS
)/2 400mV. The
V REF
0V
C REF
C INT
REF
.