Analog Devices Inc. DC112A-B

Overview

DC112A-B from Analog Devices (formerly Linear Technology) is an IrDA-compliant demonstration board implementing a complete infrared transmitter/receiver system based on the LT1328 photodiode receiver IC. It supports SIR (up to 115 kbaud), FIR (1.15 Mbaud), and 4PPM (4 Mbps) data links, features configurable MODE jumper for data-rate selection, TTL-level DATA output (Pin 5 of LT1328), and onboard HSDL-4220 LED transmitter with BPV22NF photodiode receiver.

For engineers reviewing the DC112A-B datasheet, DC112A-B pinout, DC112A-B application, or DC112A-B equivalent, this evaluation board enables rapid validation of IrDA physical-layer performance-including pulse fidelity, range testing at 1 cm and 1 m, interference rejection under ambient light, and modulation-specific timing compliance for serial infrared, fast infrared, and 4 MHz pulse-position modulation systems.

Technical Context

The DC112A-B implements dual-path signal conditioning: the LT1328 receiver uses a transimpedance preamp, high-pass servo filter (pole set by C4 = 330 pF for >200 kHz passband), and comparator with TTL output logic-where HIGH = no light, LOW = detected pulse. The MODE pin (LT1328 Pin 7) selects between SIR (MODE = VCC, adds C1 in parallel with C4) and FIR/4PPM (MODE = GND).

Transmitter functionality is discrete: Q1/Q2 2N7002 MOSFETs drive the HSDL-4220 LED via R3 (6.3 Ω), with input compatibility to 5 V TTL logic. Power is supplied via single 5 V rail; quiescent current draw is dominated by LT1328's 2 mA and LED bias during transmission.

Key Specifications

Availability

DC112A-B is available at Aetrix Electronics and suitable for IrDA protocol validation, optical link range testing, ambient light interference evaluation, and embedded infrared interface development requiring stable component supply and documented reference design implementation.

Supply support for DC112A-B includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017; Linear originally designed and qualified the DC112A-B as part of its precision analog and interface demonstration platform family.

The DC112A-B belongs to Linear's legacy demonstration board product line, engineered specifically to accelerate prototyping and characterization of IrDA-compliant infrared data links using the LT1328 receiver and discrete LED driver architecture.

FAQ

What is the function of the MODE jumper on the DC112A-B?

The MODE jumper on the DC112A-B configures the LT1328's internal servo filter pole: when set to SIR, it connects Pin 7 (MODE) to VCC, enabling C1 (10 nF) in parallel with C4 (330 pF) to lower the high-pass cutoff for slower data rates; when set to FIR/4PPM, MODE is grounded, yielding a higher cutoff (~200 kHz) required for 1.15 Mbaud and 4 Mbps operation. This setting directly determines which IrDA modulation scheme the DC112A-B will correctly demodulate.

Can the DC112A-B operate with a 3.3 V supply instead of 5 V?

No - the DC112A-B is designed for 5 V operation only. The LT1328CS8 requires a minimum 4.5 V supply per its datasheet, and the HSDL-4220 LED driver circuit (Q1/Q2 + R3) is biased for 5 V TTL logic levels and 100 mA peak current. Using 3.3 V would result in insufficient LED drive, degraded signal-to-noise ratio at the photodiode, and failure to meet IrDA timing specifications. The DC112A-B does not include level-shifting or voltage regulation for alternate supplies.

How is the DATA output of the DC112A-B electrically defined?

The DATA output (E4 on the DC112A-B board, corresponding to Pin 5 of the LT1328CS8) provides a TTL-compatible digital signal: logic HIGH (≥2.4 V) indicates absence of detected IR light; logic LOW (≤0.8 V) indicates successful detection of a valid IR pulse. This active-low behavior matches IrDA physical layer expectations, and the output drives standard TTL loads without buffering. Rise/fall times are <20 ns, verified in Figures 3–5 of the DC112A-B demo manual.

Does the DC112A-B include ESD protection for the photodiode or LED inputs?

No explicit on-board ESD protection components (e.g., TVS diodes or polymer suppressors) are shown in the DC112A-B schematic or parts list. The BPV22NF photodiode has inherent junction capacitance and moderate ESD tolerance (HBM ±500 V), and the HSDL-4220 LED is rated for HBM ±2 kV, but the DC112A-B layout provides no additional transient suppression. Users handling the board must observe standard ESD precautions, especially when connecting external cables or probing the IN, DATA, or MODE pins.

What oscilloscope setup is recommended to verify DC112A-B operation per Figures 3–5?

To replicate the waveforms in Figures 3–5 of the DC112A-B demo manual, use a 100 MHz+ bandwidth oscilloscope with 10× passive probes. Connect the probe ground to E1 (GND) and the signal tip to E4 (DATA). Drive the IN pin (E6) with a TTL-compatible pulse generator set to the target IrDA mode (e.g., 115 kbaud NRZ for SIR). Trigger on the IN signal, and ensure coaxial termination (50 Ω) at the generator output to preserve edge integrity. Ambient lighting must be controlled to avoid saturation of the BPV22NF photodiode during testing.