© 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 8

µA. 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 500

µV 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.