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READING DATA

PARALLEL OUTPUT (After a Conversion)

PARALLEL OUTPUT (During a Conversion)

ADS8515

SLAS460A – JUNE 2007 – REVISED NOVEMBER 2007

The ADS8515 outputs full or byte-reading parallel data in binary 2's complement data output format. The parallel

output is active when R/C (pin 24) is high and CS (pin 25) is low. Any other combination of CS and R/C 3-states

the parallel output. Valid conversion data can be read in a full parallel, 16-bit word or two 8-bit bytes on pins 6-13

and pins 15-22. BYTE (pin 23) can be toggled to read both bytes within one conversion cycle. Refer to Table 2

for ideal output codes and Figure 20 for bit locations relative to the state of BYTE.

Table 2. Ideal Input Voltages and Output Codes

DIGITAL OUTPUT BINARY 2's COMPLEMENT

DESCRIPTION

ANALOG INPUT

BINARY CODE

HEX CODE

Full-scale range

±10 V

Least significant bit (LSB)

305

µV

Full scale (10 V-1 LSB)

9.999695 V

0111 1111 1111 1111

7FFF

Midscale

0 V

0000 0000 0000 0000

0000

One LSB below midscale

-305

µV

1111 1111 1111 1111

FFFF

-Full scale

-10 V

1000 0000 0000 0000

8000

After conversion n is completed and the output registers have been updated, BUSY (pin 26) goes high. Valid

data from conversion n is available on D15-D0 (pins 6-13 and 15-22). BUSY going high can be used to latch the

data. Refer to Table 3 and Figure 21, Figure 22, and Figure 23 for timing specifications.

high; this may result in reading invalid data. Refer to Table 3 and Figure 21, Figure 22, and Figure 23 for timing

specifications.

Note: For the best possible performance, data should not be read during a conversion. The switching noise of

the asynchronous data transfer can cause digital feedthrough degrading the converter's performance.

The number of control lines can be reduced by tying CS low while using the falling edge of R/C to initiate

conversions and the rising edge of R/C to activate the output mode of the converter. See Figure 21.

Table 3. Conversion Timing

SYMBOL

DESCRIPTION

MIN

TYP

MAX

UNITS

Pulse duration, convert

40

ns

Access time, data valid after R/C low

0.8

1.2

µs

Propagation delay time, BUSY from R/C low

6

20

ns

Pulse duration, BUSY low

2

µs

Delay time, BUSY after end of conversion

5

ns

Delay time, aperture

5

ns

Conversion time

2

µs

Acquisition time

2

µs

Disable time, bus

10

15

83

ns

Delay time, BUSY after data valid

35

50

ns

Valid time, previous data remains valid after R/C low

1.5

2

µs

Throughput time

4

µs

Setup time, R/C to CS

10

ns

Cycle time between conversions

4

µs

Enable time, bus

10

15

30

ns

Delay time, BYTE

10

15

30

ns

10

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