DIGITAL OUTPUTS
OVERRANGE OUTPUT
The format of the output data (D0-D9) is straight binary. (See
table II.) The outputs are latched on the rising edge of CLK
with a propagation delay of 14 ns (typ). There is a one clock
cycle latency between CLK and the valid output data. (See
timing diagram.)
The OVERRANGE OUTPUT (D10) is an indication that the
analog input signal has exceeded the positive full scale input
voltageby1LSB.Whenthisconditionoccurs,D10willswitch
to logic 1. All other data outputs (D0 to D9) will remain at
logic 1 as long as D10 remains at logic 1. This feature makes
it possible to include the SPT7824 into higher resolution
systems.
Table II - Output Data Information
ANALOG INPUT
OVERRANGE
D1O
OUTPUT CODE
D9-DO
EVALUATION BOARD
>+2.0 V + 1/2 LSB
+2.0 V -1 LSB
0.0 V
1
11 1111 1111
11 1111 111Ø
ØØ ØØØØ ØØØØ
OO OOOO OOOØ
OO OOOO OOOO
The EB7824 Evaluation Board is available to aid designers in
demonstrating the full performance of the SPT7824. This
board includes a reference circuit, clock driver circuit, output
data latches and an on-board reconstruction of the digital
data. An application note describing the operation of this
board as well as information on the testing of the SPT7824 is
also available. Contact the factory for price and availability.
O
O
O
O
-2.0 V +1 LSB
<-2.0 V
(Ø indicates the flickering bit between logic 0 and 1).
The rise times and fall times of the digital outputs are not
symmetrical. The propagation delay of the rise time is typi-
cally 14 ns and the fall time is typically 6 ns. (See figure 5.)
The nonsymmetrical rise and fall times create approximately
8 ns of invalid data.
Figure 5 - Digital Output Characteristics
N
N+1
CLK In
2.4 V
Rise Time
6 nsec
6 ns
typ.
3.5 V
Invalid
Data
Invalid
Data
Data Out
(Actual)
2.4 V
(N)
(N-1)
(N-2)
0.8 V
0.5 V
tpd1
(14 ns typ.)
Invalid
Data
Data Out
(Equivalent)
Invalid
Data
(N-1)
(N-2)
(N-1)
SPT7824
8
3/11/97
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
