Datasheet AD7811, AD7812 (Analog Devices)

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2.7 V to 5.5 V, 350 kSPS, 10-Bit 4-/8-Channel Sampling ADCs AD7811/AD7812 FEATURES
The control registers of the AD7811 and AD7812 allow the
10-Bit ADC with 2.3
␮
s Conversion Time
input channels to be configured as single-ended or pseudo
The AD7811 has Four Single-Ended Inputs that
differential. The control register also features a software convert
Can Be Configured as Three Pseudo Differential
start and a software power-down. Two of these devices can
Inputs with Respect to a Common, or as Two Inde-
share the same serial bus and may be individually addressed in
pendent Pseudo Differential Channels
a multipackage application by hardwiring the device address pin.
The AD7812 has Eight Single-Ended Inputs that Can
The AD7811 is available in a small, 16-lead 0.3" wide, plastic
Be Configured as Seven Pseudo Differential Inputs
dual-in-line package (mini-DIP), in a 16-lead 0.15" wide, Small
with Respect to a Common, or as Four Independent
Outline IC (SOIC) and in a 16-lead, Thin Shrink Small Out-
Pseudo Differential Channels
line Package (TSSOP). The AD7812 is available in a small,
Onboard Track and Hold
20-lead 0.3" wide, plastic dual-in-line package (mini-DIP), in a
Onboard Reference 2.5 V
ⴞ
2.5%
20-lead, Small Outline IC (SOIC) and in a 20-lead, Thin Shrink
Operating Supply Range: 2.7 V to 5.5 V
Small Outline Package (TSSOP).
Specifications at 2.7 V–3.6 V and 5 V
ⴞ
10% DSP-/Microcontroller-Compatible Serial Interface PRODUCT HIGHLIGHTS High Speed Sampling and Automatic Power-Down Modes
1. Low Power, Single Supply Operation
Package Address Pin on the AD7811 and AD7812 Allows
Both the AD7811 and AD7812 operate from a single 2.7 V
Sharing of the Serial Bus in Multipackage Applications
to 5.5 V supply and typically consume only 10 mW of power.
Input Signal Range: 0 V to V
The power dissipation can be significantly reduced at
REF Reference Input Range: 1.2 V to V
lower throughput rates by using the automatic power-
DD Qualified for Automotive Applications
down mode e.g., 315 µW @ 10 kSPS, VDD = 3 V—see
GENERAL DESCRIPTION
Power vs. Throughput. The AD7811 and AD7812 are high speed, low power, 10-bit 2. 4-/8-Channel, 10-Bit ADC A/D converters that operate from a single 2.7 V to 5.5 V supply. The AD7811 and AD7812 have four and eight single-ended The devices contain a 2.3 µs successive approximation A/D input channels respectively. These inputs can be configured converter, an on-chip track/hold amplifier, a 2.5 V on-chip refer- as pseudo differential inputs by using the Control Register. ence and a high speed serial interface that is compatible with the 3. On-chip 2.5 V (± 2.5%) reference circuit that is powered serial interfaces of most DSPs (Digital Signal Processors) and down when using an external reference. microcontrollers. The user also has the option of using an exter- nal reference by connecting it to the V 4. Hardware and Software Control REF pin and setting the EXTREF bit in the control register. The V The AD7811 and AD7812 provide for both hardware and REF pin may be tied to V software control of Convert Start and Power-Down. DD. At slower throughput rates the power-down mode may be used to automatically power down between conversions.
FUNCTIONAL BLOCK DIAGRAMS C REF V C REF V REF IN DD AGND DGND REF IN DD AGND DGND 1.23V 1.23V REF AD7812 REF AD7811 CLOCK CLOCK OSC OSC BUF BUF DOUT DOUT V DIN CHARGE DIN IN1 CHARGE SERIAL SERIAL REDISTRIBUTION RFS VIN2 REDISTRIBUTION RFS PORT PORT DAC DAC TFS VIN3 TFS V V IN4 SCLK IN1 SCLK MUX V V IN5 IN2 MUX V V IN6 IN3 CONTROL CONTROL V V IN7 LOGIC IN4 LOGIC V VDD/3 DD /3 COMP V COMP IN8 A0 CONVST A0 CONVST
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Document Outline Features General Description Product Highlights Functional Block Diagram Specifications Timing Characteristics Absolute Maximum Ratings ESD Caution Pin Configurations Pin Function Descriptions Terminology Signal to (Noise + Distortion) Ratio Total Harmonic Distortion Peak Harmonic or Spurious Noise Intermodulation Distortion Channel-to-Channel Isolation Relative Accuracy Differential Nonlinearity Offset Error Offset Error Match Gain Error Gain Error Match Track/Hold Acquisition Time Control Register (AD7811) Control Register (AD7812) Circuit Description Converter Operation Typical Connection Diagram Analog Input DC Acquisition Time AC Acquisition Time On-Chip Reference ADC Transfer Function Power-Down Options Power-On-Reset Power-Up Times Mode 2 Full Power-Down (PD1 = 1, PD0 = 0) Mode 2 Partial Power-Down (PD1 = 0, PD0 = 1) Power vs. Throughput Operating Modes Mode 1 Operation (High Speed Sampling) Mode 2 Operation (Automatic Power-Down) Serial Interface Simplifying the Serial Interface Microprocessor Interfacing AD7811/AD7812 to PIC16C6x/7x AD7811/AD7812 to MC68HC11 AD7811/AD7812 to 8051