Data Sheet
Table 1: Data Format Description for 2V Full Scale Range
pp
Output data: Dx_12 : Dx_0
Output Data: Dx_12 : Dx_0
(DFRMT = 1, 2’s complement)
Differential Input Voltage (IPx - INx)
(DFRMT = 0, offset binary)
1 1111 1111 1111
1 0000 0000 0000
0 1111 1111 1111
0 0000 0000 0000
1.0 V
+0.24mV
-0.24mV
-1.0V
0 1111 1111 1111
0 0000 0000 0000
1 1111 1111 1111
1 0000 0000 0000
Reference Voltages
Operational Modes
The operational modes are controlled with the PD_N and
SLP_N pins. If PD_N is set low, all other control pins are
overridden and the chip is set in Power Down mode. In
this mode all circuitry is completely turned off and the
internal clock is disabled. Hence, only leakage current
contributes to the Power Down Dissipation. The startup
time from this mode is longer than for other idle modes
as all references need to settle to their final values before
normal operation can resume.
The reference voltages are internally generated and buff-
ered based on a bandgap voltage reference. No external
decoupling is necessary, and the reference voltages are
not available externally. This simplifies usage of the ADC
since two extremely sensitive pins, otherwise needed, are
removed from the interface.
If a lower full scale range is required the 13-bit output
word provides sufficient resolution to perform digital scaling-
with an equivalent impact on noise compared to adjusting
the reference voltages.
The SLP_N bus can be used to power down each channel
independently, or to set the full chip in Sleep Mode. In this
mode internal clocking is disabled, but some low band-
width circuitry is kept on to allow for a short startup time.
However, Sleep Mode represents a significant reduction in
supply current, and it can be used to save power even for
short idle periods.
A simple way to obtain 1.0V input range with a 12-bit
pp
output word is shown in the table on page 10. Note that
only 2‘s complement output data are available in this
mode and that out of range conditions must be deter-
mined based on a two bit output. The output code will
wrap around when the code goes outside the full scale
range. The out of range bits should be used to clamp the
output data for overrange conditions.
The input clock could be kept running in all idle modes.
However, even lower power dissipation is possible in
Power Down mode if the input clock is stopped. In this
case it is important to start the input clock prior to en-
abling active mode.
Table 2: Data Format Description for 1V Full Scale Range
pp
Differential Input
Voltage
Output data: Dx_11:
Dx_0 (DFRMT = 0)
(2’s Complement)
Output Data: Dx_11:
Out of Range
Out of Range
(Use Logical AND Function for &)
Dx_0 (DFRMT = 1)
(Use Logical AND Function for &)
(IPx - INx)
(2’s Complement)
0111 1111 1111
0111 1111 1111
0000 0000 0000
1111 1111 1111
1000 0000 0000
1000 0000 0000
> 0.5V
0.5V
0111 1111 1111
0111 1111 1111
0000 0000 0000
1111 1111 1111
1000 0000 0000
1000 0000 0000
Dx_12 = 1 & Dx_11 = 1
D_12 = 0 & D_11 = 1
+0.24mV
-0.24mV
-0.5V
< -0.5V
Dx_12 = 0 & Dx_11 = 0
Dx_12 = 1 & Dx_11 = 0
©2009 CADEKA Microcircuits LLC
www.cadeka.com
14
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