TC510COG datasheet(13/17 Pages) TELCOM

13 / 17 page

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TELCOM SEMICONDUCTOR, INC.

PRECISION ANALOG FRONT ENDS

TC500

TC500A

TC510

TC514

USING THE TC510/514

Negative Supply Voltage Converter (TC510, TC514)

A capacitive charge pump is employed to invert the

voltage on VDD for negative bias within the TC510/514. This

voltage is also available on the V

–

OUT pin to provide negative

bias elsewhere in the system. Two external capacitors are

required to perform the conversion.

Timing is generated by an internal state machine driven

from an on-board oscillator. During the first phase, capacitor

CF is switched across the power supply and charged to V

This charge is transferred to capacitor C

–

OUT during the

second phase. The oscillator normally runs at 100kHz to

ensure minimum output ripple. This frequency can be re-

duced by placing a capacitor from OSC to VDD. The relation-

ship between the capacitor value is shown in the typical

characteristics curves at the end of this data sheet.

Analog Input Multiplexer (TC514)

The TC514 is equipped with a four input differential

analog multiplexer. Input channels are selected using select

inputs (A1, A0). These are high-true control signals

(i.e., channel 0 is selected when (A1, A0 = 00).

EVALUATION KIT (TC500EV)

The TC500EV consists of a pre-assembled, 4 inch by 6

inch printed circuit board that connects to the serial port of

any PC or dumb terminal. Design software is also included.

TC500EV helps reduce design time and optimize converter

performance. Please contact your local TelCom representa-

tive for more information.

Design Example

Given:

Required Resolution:

16 Bits (65,536 counts).

Maximum VIN:

±2V

Power Supply Voltage: +5V

60Hz System

Step 1: Pick integration time (tINT) as a multiple of the

line frequency:

1/60Hz = 16.6msec. Use 4x line frequency = 66msec

Step 2: Calculate RINT

RINT (in MΩ) = VINMAX/20 = 2/20 = 100kΩ

Step 3: Calculate CINT for maximum (4V) integrator

output swing:

CINT (in µF) = (tINT) (20 x 10 –6) / (VS – 0.9)

= (.066) (20 x 10 –6) / (4.1)

= .32

µF (use closest value: 0.33µF)

NOTE: TelCom recommended capacitor:

WIMA p/n: MK12 .33/63/10

Step 4: Choose CREF and CAZ based on conversion rate:

Conversions/sec

= 1/(tAZ + tINT + 2 tINT + 2msec)

= 1/(66msec + 66msec +132msec+2msec)

= 3.7 conversions/sec

From which CAZ = CREF = 0.22µF (see Table 1)

NOTE: TelCom recommended capacitor:

WIMA p/n: MK12 .22/63/10

Step 5: Calculate VREF

VREF (in Volts) = (VS – 0.9) (CINT) (RINT)

2(tINT)

= (4.1) (0.33 x 10

–6) (105) / 2(.066)

= 1.025V

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