2002 Microchip Technology Inc. DS21343B-page 5
TC1034/TC1035
3.0 DETAILED DESCRIPTION
The TC1034/TC1035 is one of a series of very low
power, linear building block products targeted at low
voltage, single supply applications. The TC1034/
TC1035 minimum operating voltage is 1.8V and
maximum supply current is only 8µA. The TC1034 is a
single op amp in a 5-Pin SOT-23A package, and the
TC1035 is a single op amp with shutdown input in a
6-Pin SOT-23A package.
Microchip’s op amps are internally compensated to be
unity gain stable and have a typical gain bandwidth
product of 90kHz with typical slew rates of 35V/msec.
The amplifier’s input range extends beyond both
supplies by 200mV and the outputs will swing to within
several millivolts of the supplies depending on the load
current being driven.
Input offset voltage is 500µV max at 25°C with an input
bias current of less than 100pA. This makes these
devices extremely suitable for precision, low power
applications.
4.0 TYPICAL APPLICATIONS
The TC1034/TC1035 lends itself to a wide variety of
applications, particularly in battery powered systems. It
typically finds applications in power management,
processor supervisory and interface circuitry.
4.1 Voice Band Receive Filter
The majority of spectral energy for human voices is
found to be in a 2.7kHz frequency band from 300Hz to
3kHz. To properly recover a voice signal in applications
such as radios, cellular phones and voice pagers, a low
power bandpass filter that is matched to the human
voice spectrum can be implemented using Microchip’s
CMOS op amps. Figure 4-1 shows a unity gain multi-
pole Butterworth filter with ripple less than 0.15dB in
the human voice band. The lower 3dB cut-off frequency
is 70Hz (single order response), while the upper cut-off
frequency is 3.5kHz (fourth order response).
4.2 Supervisory Audio Tone (SAT)
Filter for Cellular
Supervisory Audio Tones (SAT) provide a reliable
transmission path between cellular subscriber units
and base stations. The SAT tone functions much like
the current/voltage used in land line telephone systems
to indicate that a phone is off the hook. The SAT tone
may be one of three frequencies: 5970, 6000 or
6030Hz. A loss of SAT implies that channel conditions
are impaired and if SAT is interrupted for more than 5
seconds a cellular call is terminated.
Figure 4-2 shows a high Q (30) second order SAT
detection bandpass filter using Microchip’s CMOS op
amp architecture. This circuit nulls all frequencies
except the three SAT tones of interest.
