Datasheet AD8260 (Analog Devices)

High Current Driver Amplifier and Digital VGA/Preamplifier with 3 dB Steps Data Sheet AD8260 FEATURES FUNCTIONAL BLOCK DIAGRAM VOCM INPP INRP INRN INPN TXFB VNEG VNEG High current driver 32 31 30 29 28 27 26 25 Differential input—direct drive from DAC Preset gain: 1.5× 1.5kΩ 1kΩ 1kΩ 1.5kΩ −3 dB bandwidth: 195 MHz VMDO 1 24 TXOP Large output drive: >±300 mA + – GM ×1 VGA/preamplifier TXEN 2 23 TXOP HIGH CURRENT DRIVER Low noise VMDI AD8260 Voltage noise: 2.4 nV/√Hz 3 22 VPOS VMID Current noise: 5 pA/√Hz VNCM 4 21 VPOS −3 dB bandwidth: 230 MHz BIAS Gain range: 30 dB in 3 dB steps VPSB 5 20 VPSR −6 dB to +24 dB (for preamplifier gain of 6 dB) VGA/PREAMPLIFIER Single-ended preamplifier input and differential VGA ENBL 6 19 VMDO ATTENUATOR output VGAP 7 18 PRAI Supplies: 3.3 V to 10 V (with VMID enabled) GM STAGES ±3.3 V to ±5 V (with VMID disabled) VGAN 8 17 FDBK Power: 93 mW with 3.3 V supplies LOGIC Power-down for VGA, driver amplifier, and system
01
9
0
10 11 12 13 14 15 16
2- 19
APPLICATIONS VNGR VPSR GNS3 GNS2 GNS1 GNS0 PRAO VNGR
07 Figure 1. Functional Block Diagram
Digital AGC systems Tx/Rx signal processing Power line transceivers GENERAL DESCRIPTION
The AD8260 includes a high current driver, usable as a dynamic range, it is essential that the part be ac-coupled when transmitter, and a low noise digitally programmable variable operating on a single supply. gain amplifier (DGA), useable as a receiver. The AD8260 preamplifier (PrA) is configured with external The receiver section consists of a single-ended input preampli- resistors for gains greater than 6 dB and can be inverting or fier, and linear-in-dB, differential-output DGA. The receiver has noninverting. The DGA is characterized with a noninverting a small signal –3 dB bandwidth of 230 MHz; the driver small preamplifier gain of 2×. The attenuator has a range of 30 dB and signal bandwidth is 195 MHz. The driver delivers ±300 mA, the output amplifier has a gain of 8× (18.06 dB). The lowest well suited for driving low impedance loads, even when noninverting gain range is −6 dB to +24 dB and shifts up with connected to a 3.3 V supply. increased preamplifier gain. The gain is controlled via a parallel The AD8260 DGA is ideal for trim applications and has a gain port (Pin GNS0 to Pin GNS3) with 10 gain steps of 3 dB per span of 30 dB, in 3 dB steps. Excellent bandwidth uniformity is code. The preamplifier and DGA are disabled for any code that maintained across the entire frequency range. The low output- is not assigned a gain step. referred noise of the DGA is advantageous in driving high The AD8260 can operate with single or dual supplies from 3.3 V speed ADCs. The differential output facilitates the interface to to ±5 V. An internal buffer normally provides a split supply modern low voltage high speed ADCs. reference for single-supply operation; an external reference can Single-supply and dual-supply operation makes the part versatile also be used when the VMID buffer is shut down. and enables gain control of negative-going pulses, such as those The operating temperature range is −40°C to +105°C. The generated by photodiodes or photo-multiplier tubes, as well as AD8260 is available in a 5 mm × 5 mm, 32-lead LFCSP. processing band-pass signals on a single supply. For maximum
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Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TEST CIRCUITS THEORY OF OPERATION OVERVIEW HIGH CURRENT DRIVER AMPLIFIER PRECAUTIONS TO BE OBSERVED DURING HALF-DUPLEX OPERATION VMID BUFFER PREAMPLIFIER PREAMPLIFIER NOISE DGA GAIN CONTROL OUTPUT STAGE ATTENUATOR SINGLE-SUPPLY OPERATION AND AC COUPLING POWER-UP/POWER-DOWN SEQUENCE LOGIC INTERFACES APPLICATIONS INFORMATION EVALUATION BOARD CONNECTING THE EVALUATION BOARD OUTLINE DIMENSIONS ORDERING GUIDE