Datasheet

Channel1AIntegrates Channel1BIntegrates
Channel1B
Converts
Channel1A
Converts
Channel1B
Converts
Channel2AIntegrates Channel2BIntegrates
Channel2B
Converts
Channel2A
Converts
Channel2B
Converts
CHANNEL1
CHANNEL2
DDC112 www.ti.com
The DDC112 continuously integrates the input signal by incorporating one dual integrator (A and B) per
input channel. The output of the dual integrators are multiplexed into the A/D converter. In operation, one
side of each input integrates the input charge, while the other side is being converted by the delta-sigma
A/D converter and then reset. Figure 3 illustrates this operation. Another unique feature of the DDC112 is
the option of external integrating capacitors. This option allows a user-programmable full-scale range. On
the DDC112EVM evaluation fixture, sockets are provided on the device under test (DUT) board (P
13
to
P
20
) to allow for easy insertion of these optional capacitors.
Figure 3. Integration/Conversion Timing of a Dual DDC112 A/D Converter
The gain of the DDC112 can be programmed to seven predetermined values through the software.
Likewise, a user can install four external capacitors (C10, C11, C12, and C13) and design in a custom
gain setting. Table 1 summarizes the available gain options.
Table 1. Input Ranges vs Gain Settings
for the DDC112
(1)
Input Range Integration Capacitor (Nominal)
Q
IN
Range (pC) C
INT
(pF)
–0.2 to 50 12.5 (internal)
–0.4 to 100 25.0 (internal)
–0.6 to 150 37.5 (internal)
–0.8 to 200 50.0 (internal)
–1.0 to 250 62.5 (internal)
–1.2 to 300 75.0 (internal)
–1.4 to 350 87.5 (internal)
–4.0 to 1000 250 (external)
(1)
In this example, the integration time is 1 ms.
4
DDC11xEVM-PDK User's Guide SLAU234A–October 2007–Revised July 2010
Copyright © 2007–2010, Texas Instruments Incorporated