CS5014 datasheet(13/46 Pages) CIRRUS

13 / 46 page

All calibration, conversion, and throughput times

directly scale to CLKIN frequency. Thus,

throughput can be precisely controlled and/or

maximized using an external CLKIN signal. In

contrast, the CS5012A/14/16’s internal oscillator

will vary from unit-to-unit and over temperature.

The CS5012A/14/16 can typically convert with

CLKIN as low as 10 kHz at room temperature.

Initiating Conversions

A falling transition on the HOLD pin places the

input in the hold mode and initiates a conversion

cycle. Upon completion of the conversion cycle,

the CS5012A/14/16 automatically return to the

track mode. In contrast to systems with separate

track-and-holds and A/D converters, a sampling

clock can simply be connected to the HOLD in-

put (Figure 3a). The duty cycle of this clock is

not critical. It need only remain low at least one

CLKIN cycle plus 50 ns, but no longer than the

minimum conversion time or an additional con-

version cycle will be initiated with inadequate

time for acquisition.

Microprocessor-Controlled Operation

Sampling and conversion can be placed under

microprocessor control (Figure 4) by simply gat-

ing the devices’ decoded address with the write

strobe for the HOLD input. Thus, a write cycle to

the CS5012A/14/16’s base address will initiate a

conversion. However, the write cycle must be to

the odd address (A0 high) to avoid initiating a

software controlled reset (see Reset below).

The calibration control inputs, CAL, and

INTRLV are inputs to a set of transparent latches.

These signals are internally latched by CS return-

ing high. They must be in the appropriate state

whenever the chip is selected during a read or

write cycle. Address lines A1 and A2 are shown

connected to CAL and INTRLV in Figure 4 plac-

ing calibration under microprocessor control as

well. Thus, any read or write cycle to the

CS5012A/14/16’s base address will initiate or ter-

minate calibration. Alternatively, A0, INTRLV,

and CAL may be connected to the microproces-

sor data bus.

Conversion Time/Throughput

Upon completing a conversion cycle and return-

ing to the track mode, the CS5012A/14/16

require time to acquire the analog input signal

before another conversion can be initiated. The

acquisition time is specified as six CLKIN cycles

plus 2.25

µs (1.32 µs for the CS5012A -7 version

only). This adds to the conversion time to define

the converter’s maximum throughput. The con-

version time of the CS5012A/14/16, in turn,

depends on the sampling, calibration, and CLKIN

conditions.

HOLD

CS5012A/14/16

Addr

Dec

Address

Bus

INTRLV

CAL

ADDR VALID

Figure 4b. Conversions under Microprocessor Control

CS5012A/14/16

Addr

Dec

Address

Bus

CONCLK

HOLD

INTRLV

CAL

ADDR VALID

Figure 4a. Conversions Asynchronous to CLKIN

CS5012A, CS5014, CS5016

DS14F6

2-19

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