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Design Notes

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  RS232 Interface Circuits for 3.3V Systems &mdash DN75
  PDF, 105 Kb, File published: Oct 1, 1993
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  RS232 Interface Circuits for 3.3V Systems – Design Note 75 Gary Maulding
  The rapid, widespread use of 3.3V logic circuits complicates the selection of RS232 interface circuits. The
  optimum choice of an interface circuit should be based
  upon several application dependent factors:
  1) Logic circuitry connected to interface chip port mouse. The LTВ®1342, LT1330, and LT1331 are all
  good RS232 transceiver choices for systems with both
  5V and 3V power. Typical performance waveforms for
  the LT1342 operating with VCC = 5V and VL = 3.3V are
  shown in Figure 2. 2) Power supply voltages available
  RECEIVER
  OUTPUT 3) Power consumption constraints
  4) Serial interface environment
  5) Mouse driving requirements
  As Figure 1 illustrates, 5V interface circuits cannot be
  used to directly connect to 3.3V CMOS logic circuits.
  The receiver output level will forward bias the logic
  circuit’s input protection diode, causing large current
  flow. In the worst case the CMOS logic circuit may
  latch up. Resistor voltage dividers or level shift buffers may be used to prevent forward biasing the CMOS
  input diode, but an RS232 transceiver designed for 3V
  logic application prevents this problem without extra
  components or power dissipation.
  Many of today’s systems have both 5V and 3V power …

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Manufacturer's Classification

• Interface > RS232/RS562 Transceivers

Other Names:

LT1342CSWPBF, LT1342CSW PBF