DDC118 Datasheet, PDF (1/30 Pages) Burr-Brown (TI) – Octal Current Input 20-Bit Analog-To-Digital Converter

DDC118
SBAS325A − JUNE 2004 − REVISED JUNE 2005
Octal Current Input 20-Bit
Analog-To-Digital Converter
FEATURES
D SINGLE-CHIP SOLUTION TO DIRECTLY
MEASURE EIGHT LOW-LEVEL CURRENTS
D HIGH PRECISION, TRUE INTEGRATING
FUNCTION
D INTEGRAL LINEARITY:
±0.01% of Reading ±0.5ppm of FSR
D VERY LOW NOISE: 5.2ppm of FSR
D LOW POWER: 13.5mW/channel
D ADJUSTABLE DATA RATE: Up to 3.125kSPS
D PROGRAMMABLE FULL SCALE
D DAISY-CHAINABLE SERIAL INTERFACE
AVDD
IN1
Dual
Switched
Integrator
IN3
Dual
Switched
Integrator
IN2
Dual
Switched
Integrator
IN4
Dual
Switched
Integrator
IN5
Dual
Switched
Integrator
IN7
Dual
Switched
Integrator
IN6
Dual
Switched
Integrator
IN8
Dual
Switched
Integrator
AGND
VREF
∆Σ
Modulator
DVDD
Digital
Filter
Control
CLK
CONV
RANGE0
RANGE1
RANGE2
TEST
CLK_4X
HISPD/LOPWR
RESET
∆Σ
Modulator
Digital
Filter
FORMAT
DCLK
DCLK
∆Σ
Modulator
Digital
Filter
Digital
Input/Output
DVALID
DOUT
DOUT
DIN
DIN
∆Σ
Digital
Modulator
Filter
DGND
APPLICATIONS
D CT SCANNER DAS
D PHOTODIODE SENSORS
D INFRARED PYROMETER
D LIQUID/GAS CHROMATOGRAPHY
Protected by US Patent #5841310
DESCRIPTION
The DDC118 is a 20-bit octal channel, current-input
analog-to-digital (A/D) converter. It combines both
current-to-voltage and A/D conversion so that eight
low-level current output devices, such as photodiodes, can
be directly connected to its inputs and digitized.
For each of the eight inputs, the DDC118 provides a
dual-switched integrator front-end. This design allows for
continuous current integration: while one integrator is
being digitized by the onboard A/D converter, the other is
integrating the input current. Adjustable full-scale ranges
from 12pC to 350pC and adjustable integration times from
50µs to 1s allow currents from fAs to µAs to be measured
with outstanding precision. Low-level linearity is ±0.5ppm
of the full-scale range and noise is 5.2ppm of the full-scale
range.
Two modes of operation are provided. In Low-Power
mode, total power dissipation is only 13.5mW per channel
with a maximum data rate of 2.5kSPS. High-Speed mode
supports data rates up to 3.125kSPS with a corresponding
dissipation of 18mW per channel.
The DDC118 has a serial interface designed for
daisy-chaining in multi-device systems. Simply connect
the output of one device to the input of the next to create
the chain. Common clocking feeds all the devices in the
chain so that the digital overhead in a multi-DDC118
system is minimal.
The DDC118 is a single-supply device using a +5V analog
supply and supporting a +2.7V to +5.25V digital supply.
Operating over the industrial temperature range of −40°C
to 85°C, the DDC118 is offered in a QFN-48 package.
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PRODUCTION DATA information is current as of publication date. Products
conform to specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
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