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PDF DS276S Data sheet ( Hoja de datos )
| Número de pieza | DS276S | |
| Descripción | Low Power Transceiver Chip | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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DS276
Low Power Transceiver Chip
FEATURES
Low-power serial transmitter/receiver for
battery-backed systems
Transmitter steals power from receive signal
line to save power
Single 3V or 5V operation
Full duplex operation up to 20k bps
Ultra-low static current
Compatible with RS-232-E signals
PIN ASSIGNMENT
RXOUT
18
VDRV+
27
TXIN
36
GND
45
VCC
RXIN
VDRV-
TXOUT
DS276 8-Pin DIP (300-mil)
DS 276S 8-Pin SOIC (150-mil)
PIN DESCRIPTION
RXOUT
VDRV+
TXIN
GND
RS-232 Receiver Output
Transmit Driver Positive Supply
RS-232 Driver Input
System Ground (0V)
TXOUT
VDRV-
RXIN
VCC
RS-232 Driver Output
Transmit Driver Negative Supply
RS-232 Receiver Input
System Logic Supply (3-5V)
ORDERING INFORMATION
DS276
8-Pin DIP
DS276S
8-Pin SOIC
DESCRIPTION
The DS276 Line-Powered RS-232 Transceiver Chip is a CMOS device that provides a low-cost, very
low-power interface to RS-232 serial ports. The receiver input translates RS-232 signal levels to common
CMOS/TTL levels. The transmitter can be used with independently supplied positive and negative
supplies, but in most cases will be used with the positive supply, sharing the logic supply and the negative
supply stolen from the receive RS-232 signal when that signal is in a negative state (marking). By using
an external reservoir capacitor and Schottky diode (see Figure 4) this negative supply can be maintained
even during full-duplex operation. Since most serial communication ports remain in a negative state
statically, using the receive signal for negative power greatly reduces the DS276’s static power
consumption. This feature is especially important for battery-powered systems such as laptop computers,
remote sensors, and portable medical instruments. During an actual communication session, the DS276’s
transmitter will use system power (3-12 volts) for positive transitions while still employing the receive
signal for negative transitions.
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DS276
NOTES:
1. This circuit as shown does not meet the RS-232 requirement for signal levels (high-level output
voltage). However, as most RS-232 receivers will interpret any voltage over 2V as a space this will
normally be of no consequence. Alternatively, VDRV+ can be supplied independently from a higher
voltage supply.
2. The capacitor is charged negatively whenever RXIN is in a marking (or idle) state. When the DS276 is
transmitting marking data and RXIN is spacing the capacitor will discharge towards ground with a
time constant determined by the capacitor value and the value of the load resistance. The value shown
should store sufficient charge for reliable operation up to 20 kbps.
3. RXIN must never be allowed to reach a negative voltage with respect to VDRV- or excessive currents
will be drawn. Therefore, if negative voltage swings are present on RXIN, VDRV- should not be
connected to ground and the circuit shown in Figure 4 should be used.
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5 Page 
STATIC OPERATING CURRENT TEST CIRCUIT Figure 10
DS276
DRIVER LEAKAGE TEST CIRCUIT Figure 11
PROPAGATION DELAY TEST CIRCUIT Figure 12
11 of 11
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet DS276S.PDF ] | |
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