Integrated Circuits

ET2010

ANALOG SIGNAL PROCESSOR with BALANCE TRIM and VARIABLE GAIN

FEATURES

• Single supply operation
• Handles Sine/Cosine inputs from DC to 125KHz
• Photodiode input photocurrent range from 100nA
• Adjustable gain
• DC offset adjustable at each output
• Interfaces directly with ET2015, ET2024, or ET2110 Interpolation devices

This part is available in a 24 lead TSSOP package, standard or Pb-Free, or as die.

DESCRIPTION

The ET2010 ASP is a monolithic bipolar ASIC designed to transform nanoamp-level differential photocurrents into 1Vpp sinewaves that are suitable for interpolation.  A gain adjustment is provided that affects all channels in concert.  Separate balance adjustments are provided for each output, for centering the waveforms on the reference voltage.  In applications where the photocurrents are generated in phased-array photodiodes, the balance adjustments are generally not needed.  In these cases, the BAL pins should be connected to GND. In most encoder designs, the LED optical output level changes with supply voltage, temperature, and age.  This causes corresponding changes in the photocurrent signal levels.  The ASP rejects these variations in the input signals, resulting in output levels that are stable over time, temperature, and supply voltage. In practice,  the maximum usable gain setting may be limited by noise considerations.  The comparators in Interpolation ASIC's have a minimal amount of hysteresis, and care must be taken that the noise is well below the hysteresis value.  If necessary, the noise can be reduced by lowering the photodiode capacitance or by rolling off the ASP outputs with RC filters.

DESIGN SPECIFICATIONS

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, V_CC=5V, T_A = 25°C, I_OFFSET = 1.5uADC, and I_IN = 750nA_(p-p) @ 100KHz. All BAL pins are tied to GND for testing.

Pin Descriptions

Application

For applications that use photodiode sensing, and are intended for interpolation of these signals, ETIC offers the ET2010 Analog Signal Processor. With photodiodes representing differential optical channels on its inputs, the device provides four channels of amplified sinewave outputs compatible with the downstream interpolation circuitry. Balance adjustment is provided to correct for amplitude differences between inputs. Sufficient gain (voltage adjustable) is provided so that amp input signals produce output sinewaves in excess of the 400mVpp required at the input of an interpolation device such as the ET2015 or ET2024. Additionally, the ET2010 provides a level shifting of these signal and provides the DC offset of 2.5V (VCC/2) used to bias the SIG_REF pin of these interpolation devices. Please see the Application Circuit for interconnection of the signal processor, an interpolation device, and a four channel ET7272 differential output line driver.

Application Circuit

ET2010-TSS

ET2010 – C

Size = .174” x .119” (4420µ x 3023µ)
Thickness = .011”-.013” (305µ-330µ)