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MagChip, MagStripe Decoding ASIC
(IDT 141)
 
MagChip Specifications

The MagChip is an Application-Specific Integrated Circuit (ASIC) specifically designed for amplifying and decoding MagStripe read head signals. Because MagChip is an Integrated Circuit (IC) designed specifically to perform reading and decoding functions, it is smaller, consumes less power, and costs less than a general-purpose processor chip while delivering superior performance. MagChip decodes the analog output from a magnetic "read" head and produces a digital data-bit stream with clock and "media detect" outputs. It has 100 levels of Automatic Gain Control (AGC), decode speeds of 3 to 75 inches per second, and uses less than 50 micro amps when not reading.

 

 

Features:

  • Superior reading of high jitter, scratched, and worn MagStripe cards

  • Low power-sleeps when not reading

  • Less than 1.0mA typical when reading a card

  • Operation form 2.7V to 5.5V

  • True AGC handles signal amplitudes from 1mV to 1V p-p

  • +/- 2000V Electro-Static Discharge (ESD) protection

  • Typical card swipe speeds from 3 to 75+ ips

  • Compatible with a wide range of available read heads

  • Supports bi-directional card swiping and decoding

Functional Description
ID TECH’s MagChip has two input pins for the connection of a magnetic read head. The head signals are amplified by MagChip using an auto-scaling amplifier. The amplified signal is used to decode the magnetic stripe signal (dual-frequency data encoded using the principals of Aiken’s F2F encoding) into a digital data format consisting of the magnetic stripe data, clock, and “media detect” outputs, all of which are CMOS level signals. Additionally, MagChip has a automatic power-down sleep mode that saves energy. The F2F data rate ranges from less than 200 to greater than 30,000 magnetic flux reversals per second, depending upon data density and the velocity at which the magnetic stripe is passed across the “read” head. One clock pulse is required for each data bit, and the “media detect” signal is held true while magnetic head signals are present.

Data Output
Data output is a serial stream of digital bits, the level of which, with the corresponding clock, represents each data bit that was recorded on the magnetic stripe track. No data filtering is required, as the first 6 to 9 bits (after MagChip wake-up) from the leading edge of a magnetic stripe are not provided as output. These bits are used for circuit synchronization. A data output high level is a ZERO value data bit, and a low level is a ONE value data bit. The data output is last-bit-first when media is passed by the head in a reverse direction.

Clock Output
Clocking output is normally high, and goes low to indicate a data sample time. The data output is stable and may be sampled on the falling or rising edge of clock, or at any time while the clock is low. The MagChip clock goes low approximately 2 μsec after the data output is valid. The clock width changes with speed. (Please refer to the AC Characteristics table for minimum/maximum signal timing.) The receiving interface for MagChip data must sense the high-to-low clock transition (leading edge) and acquire the data bit level during clock pulse.

“Media Detect” Output
This output indicates the presence of encoded magnetic media passing the read head. This signal is normally high; a low output indicates encoded media. The output is an open drain type with high impedance; the outputs of several MagChip circuits can be connected together. A pull-up resistor is needed for proper operation of this output if it is to be used.

Sleep Mode Function
The MagChip will automatically enter a power-down sleep mode when a magnetic head signal is not present. The MagChip will automatically wake-up when a magnetic head signal is present. The outputs Data, Clock, and Media Detect are at a high level during sleep mode.

 
 

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