TC1025 View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC1025

Linear Building Block – Dual Low Power Comparator

Microchip Technology 

TC1025

3.0 DETAILED DESCRIPTION

The TC1025 is one of a series of very low-power, linear

building block products targeted at low-voltage, single-

supply applications. The TC1025 minimum operating

voltage is 1.8V, and typical supply current is only 8μA.

It combines two comparators in a single package.

3.1 Comparators

The TC1025 contains two comparators. The compara-

tor’s input range extends beyond both supply voltages

by 200mV and the outputs will swing to within several

millivolts of the supplies depending on the load current

being driven.

The comparators exhibit propagation delay and supply

current which are largely independent of supply

voltage. The low input bias current and offset voltage

make them suitable for high impedance precision

applications.

4.0 TYPICAL APPLICATIONS

The TC1025 lends itself to a wide variety of

applications, particularly in battery-powered systems.

Typically, it finds application in power management,

processor supervisory, and interface circuitry.

4.1 External Hysteresis (Comparator)

Hysteresis can be set externally with two resistors

using positive feedback techniques (see Figure 4-1).

The design procedure for setting external comparator

hysteresis is as follows:

1. Choose the feedback resistor RC. Since the

input bias current of the comparator is at most

100pA, the current through RC can be set to

100nA (i.e., 1000 times the input bias current)

and retain excellent accuracy. The current

through RC at the comparator’s trip point is VR/

RC where VR is a stable reference voltage.

2. Determine the hysteresis voltage (VHY) between

the upper and lower thresholds.

3. Calculate RA as follows:

EQUATION 4-1:

RA

=

RC

⎛

⎝

V-V----DH----DY-⎠⎞

4. Choose the rising threshold voltage for VSRC

(VTHR).

5. Calculate RB as follows:

EQUATION 4-2:

RB

=

-----------------------------1-----------------------------

⎛

⎝

-V---V-R---T--×-H---R-R----A--

⎞

⎠

–R---1--A--

–

---1----

RC

6. Verify the threshold voltages with these

formulas:

VSRC rising:

EQUATION 4-3:

VTHR

=

(VR)(RA)

⎛

⎝

R---1--A--⎠⎞

+

⎛

⎝

-R--1--B--⎠⎞

+

⎛

⎝

R---1--C--⎠⎞

VSRC falling:

EQUATION 4-4:

VTHF = VTHR –

⎛

⎝

R-----A----R-×----C-V----D----D-⎠⎞

DS21656C-page 4

© 2005 Microchip Technology Inc.

Share Link: