Datasheet AD8335 (Analog Devices)

Quad Low Noise, Low Cost Variable Gain Amplifier Data Sheet AD8335 FEATURES FUNCTIONAL BLOCK DIAGRAM 1 Low noise preamplifier (PrA) 2 N P1 1 P1 M1 N 12 12 SP1 PO PO VI VC VI EN HL Voltage noise = 1.3 nV/√Hz typical Current noise = 2.4 pA/√Hz typical VOH1 NF = 7 dB (RS = RIN = 50 Ω) PIP1 ATTEN 20dB Single-ended input; V 18dB VMD1 –48dB TO TO IN maximum = 625 mV p-p PMD1 0dB 28dB Active input match VOL1 POP2 Input SNR (noise bandwidth = 20 MHz) = 92 dB PMD2 VGA INTERPOLATOR GAIN INT VGN1 18dB VMD2 PIP2 Differential output SL12 V PON2 OUT maximum = 5 V p-p, RL = 500 Ω differential INTERPOLATOR GAIN INT VGN2 Gain range (8 dB output gain step) VCM2 VOL2 −10 dB to +38 dB—low gain mode VIP2 ATTEN 20dB −2 dB to +46 dB—high gain mode –48dB TO TO VIN2 28dB 0dB Accurate linear-in-dB gain control VOH2 AD8335 PrA + VGA performance VOH3 VIN3 ATTEN 20dB −3 dB bandwidth of 85 MHz –48dB TO TO VIP3 28dB 0dB Excellent overload performance VOL3 VCM3 Supply: 5 V PON3 Power consumption INTERPOLATOR GAIN INT VGN3 95 mW/channel (380 mW total) PIP3 18dB VMD3 SL34 65 mW/channel (PrA off; 260 mW total) PMD3 Power-down INTERPOLATOR GAIN INT VGN4 POP3 VOL4 PMD4 ATTEN 20dB APPLICATIONS 18dB VMD4 –48dB TO TO PIP4 28dB 0dB VOH4 Medical imaging (ultrasound, gamma cameras) Sonar 4 4 4 Test and measurement N P4 P4 N 34 34
-001
VI SP3 PO PO VI VCM4 EN HL
976
Precise, stable wideband gain control
04 Figure 1.
GENERAL DESCRIPTION
The AD8335 is a quad variable gain amplifier (VGA) with Assuming a 20 MHz noise bandwidth (NBW), the Nyquist low noise preamplifier intended for cost and power sensitive frequency for a 40 MHz ADC, the input SNR is 92 dB. The applications. Each channel features a gain range of 48 dB, fully HLxx pin optimizes the output SNR for 10-bit and 12-bit differential signal paths, active input preamplifier matching, ADCs with 1 V p-p or 2 V p-p full-scale (FS) inputs. and user-selectable maximum gains of 46 dB and 38 dB. Channel 1 and Channel 2 are enabled through the EN12 pin, and Individual gain controls are provided for each channel. Channel 3 and Channel 4 are enabled through the EN34 pin. The preamplifier (PrA) has a single-ended to differential gain of For VGA only applications, the PrAs can be powered down, ×8 (18.06 dB) and accepts input signals ≤625 mV p-p. PrA noise is significantly reducing power consumption. 1.2 nV/√Hz and the combined input referred voltage noise of The AD8335 is available in a 64-lead lead frame chip scale the PrA and VGA is 1.3 nV/√Hz at maximum gain. package (9 mm × 9 mm) for the industrial temperature range of −40°C to +85°C.
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TEST CIRCUITS THEORY OF OPERATION ENABLE SUMMARY PREAMP Noise VGA Optimizing the System Dynamic Range Attenuator Gain Control Output Stage VGA Noise APPLICATIONS INFORMATION ULTRASOUND BASIC CONNECTIONS PREAMP CONNECTIONS INPUT OVERDRIVE Input Overload Protection LOGIC INPUTS COMMON-MODE PINS DRIVING ADCs EVALUATION BOARD BOARD LAYOUT OUTLINE DIMENSIONS ORDERING GUIDE