TC530 View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC530

5V Precision Data Acquisition Subsystems

Microchip Technology 

TC530/TC534

5.0 TYPICAL APPLICATIONS

5.1 Programming the TC530/TC534

5.1.1 AZ AND INT PHASE DURATION

These two phases have equal duration determined by

the crystal (or external) frequency and the timer initial-

ization byte (LOAD VALUE). Timing is selected as

follows:

1. Select Integration Time

Integration time must be picked as a multiple of

the period of the line frequency. For example,

TINT times of 33 ms, 66 ms and 132 ms

maximize 60 Hz line rejection.

2. Estimate Crystal Frequency

Crystal frequencies as high as 2 MHz are

allowed. Crystal frequency is estimated using:

EQUATION 5-1:

Where:

2(RES)/TINT

RES = Desired Converter Resolution (in

counts)

FIN = Input Frequency (in MHz)

INT = Integration Time (in seconds)

3. Calculate LOAD VALUE

EQUATION 5-2:

[LOAD VALUE]10 = 256 – -(--T---I--N----T---)--(---F----I-N----)

1024

FIN can be adjusted to a standard value during this

step. The resulting base, -10 LOAD VALUE, must be

converted to a hexadecimal number and then loaded

into the serial port prior to initiating A/D conversion.

5.2 DINT and IZ Phase Timing

The duration of the DINT phase is a function of the

amount of voltage stored on the integrator capacitor

during INT and the value of VREF. The DINT phase is

initiated immediately following INT and terminated

when an integrator output zero crossing is detected. In

general, the maximum number of counts chosen for

DINT is twice that of INT (with VREF chosen at

VIN(MAX)/2).

5.3 System RESET

The TC530/TC534 must be forced into the AZ state

when power is first applied. A .01 µF capacitor

connected from RESET to VDD (or external system

reset logic signal) can be used to momentarily drive

RESET high for a minimum of 100 ms.

5.4 Design Example

Figure 5-1 shows a typical TC530 interrupt-driven

application. Timing and component values are

calculated from equations and recommendations made

in Section 4.1 “Dual Slope Integrating Converter”

and Section 5.1 “Programming the TC530/TC534”

of this document. The EOC connection to the

processor INT input is for interrupt-driven applications

only. (In polled systems, the EOC output is available on

DOUT).

Given:

Required Resolution 16-bits (65,536 counts.)

(RES):

Maximum: VIN ±2V

Power Supply Voltage: +5V

60Hz System

1. Pick Integration time (TINT): 66 ms.

2. Estimate crystal frequency.

EXAMPLE 5-1:

FIN

=

2----R----E---S-

TINT

=

2-----•----6---5---5---3---6-- ≈ 2MHz

66ms

3. Calculate LOAD VALUE

EXAMPLE 5-2:

LOAD VALUE

=

256 – -(--T---I--N----T---)--(---F----I-N----)

1024

=

[ 128 ] 10

[128]10 = 80 hex

4. Calculate RINT.

EXAMPLE 5-3:

RINT

=

V----I--N----M----A---X-

20

=

--2---

20

=

100kΩ

5. Calculate CINT for maximum (4V) integrator out-

put swing:

DS21433C-page 12

© 2007 Microchip Technology Inc.

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