LTC1098ACN8 datasheet(25/32 Pages) LINER

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LTC1096/LTC1096L

LTC1098/LTC1098L

10968fc

MICROPROCESSOR INTERFACES

The LTC1096(L)/LTC1098(L) can interface directly (without

external hardware to most popular microprocessor (MPU)

synchronous serial formats (see Table 1). If an MPU without

a dedicated serial port is used, then three or four of the

MPU’s parallel port lines can be programmed to form the

serial link to the LTC1096(L)/LTC1098(L). Included here

is one serial interface example and one example showing

a parallel port programmed to form the serial interface.

Motorola SPI (MC68HC05C4,CM68HC11)

The MC68HC05C4 has been chosen as an example of

an MPU with a dedicated serial port. This MPU transfer

data MSB-ﬁrst and in 8-bit increments. With two 8-bit

transfers, the A/D result is read into the MPU. The ﬁrst

8-bit transfer sends the DIN word to the LTC1098(L) and

clocks into the processor. The second 8-bit transfer clocks

the A/D conversion result, B7 through B0, into the MPU.

ANDing the ﬁrst MUP received byte with 00Hex clears the

ﬁrst byte. Notice how the position of the start bit in the

ﬁrst MPU transmit word is used to position the A/D result

right-justiﬁed in two memory locations.

APPLICATIONS INFORMATION

TYPICAL APPLICATIONS

Effective Number of Bits

The effective number of bits (ENOBs) is a measurement

of the resolution of an A/D and is directly related to the

S/(N + D) by the equation:

ENOB = [S/(N + D) –1.76]/6.02

where S/(N + D) is expressed in dB. At the maximum sam-

pling rate of 33kHz the LTC1096 maintains 7.5 ENOBs or

better to 40kHz. Above 40kHz the ENOBs gradually decline,

as shown in Figure 12, due to increasing second harmonic

distortion. The noise ﬂoor remains approximately 70dB.

Figure 12. Dynamic Accuracy Is Maintained Up to an Input

Frequency of 40kHz

INPUT FREQUENCY (kHz)

10968 F12

fSAMPLE = 31.25kHz

Table 1. Microprocessor with Hardware Serial Interfaces

Compatible with the LTC1096(L)/LTC1098(L)

PART NUMBER

TYPE OF INTERFACE

Motorola

MC6805S2,S3

MC68HC11

MC68HC05

SPI

RCA

CDP68HC05

SPI

Hitachi

HD6305

HD63705

HD6301

HD63701

HD6303

HD64180

SCI Synchronous

CSI/O

National Semiconductor

COP400 Family

COP800 Family

NS8050U

HPC16000 Family

MICROWIRE™

MICROWIRE/PLUS™

MICROWIRE/PLUS

Texas Instruments

TMS7002

TMS7042

TMS70C02

TMS70C42

TMS32011*

TMS32020

Serial Port

*Requires external hardware

MICROWIRE and MICROWIRE/PLUS are trademarks of

National Semiconductor Corp.

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