Features

Low power consumption: ICC u003d 300μA typical value

Design for RS485 interface application

Single 5V power supply

–7V to 12V The scope of the bus commonline allows

The grounding difference between the equipment on the bus is ± 7V

Heat protection

Power/disconnect non -fault -free driver output

[

123] Allows real -time insertion or removing transceiver

Drives maintain high impedance in three states or in the case of power off

Drive output and

The receiver allows the receiver to allow The maximum of 32 transceivers on the bus

70MV typical input lag

30ns typical drive delayed with 5NS oblique sex

pins with SN75176A, DS75176A compatibility and μA96176

Low power consumption RS485/RS422 transceiver

Horizontal translation

Description

LTC485 is a low -power separation bus/line transceiver for multi -point data transmission Standard RS485 Design Expansion Co -mode range (12V to -7 volts). It also meets the requirements of RS422. The CMOS design is more than its bipolar correspondence, and the durability ESD is damaged. Drives and receivers have three state output drives output to maintain a high -impedance of the entire co -mode range. Excessive power consumption is entry into high impedance status by the hot -off circuit output by the mandatory drive output caused by the bus or failure. The receiver has a fault protection function to ensure the high output state when the input keeps open. LTC485 is in business and expanding industrial temperature.

absolute value

(Note 1)

Power voltage 12 volt

Control input voltage -0.5V to VCC+0.5V

Drive input voltage — 0.5V to VCC+0.5V

Drive output voltage ± 14 volts

The input voltage of the receiver ± 14 volts

[ 123] The receiver output voltage -0.5V to VCC+0.5V

The operating temperature range

LTC485i – 40 ° C ≤ TA ≤ 85 ° C

LTC485C 0 ° C 0 ° C 0 ° C ≤TA ≤ 70 ° C

LTC485M –55 ° C ≤ TA ≤ 125 ° C

Welding temperature (10 seconds) 300 degrees Celsius

Electric characteristics vcc u003d5V ± 5%, unless otherwise explained. (Note 2 and 3)

The switching characteristics u vcc u003d 5V ± 5%, unless there is another instructions. (Note 2 and 3)

indicates the standard temperature range suitable for the entire operation.

Note 1: The absolute maximum rated value means that the device cannot guarantee.

Note 2: The current of all entering device pins is positive; the current output from the device is positive. All voltage reference equipment is grounded, unless there are other regulations.

Note 3: All typical values u200bu200bare VCC u003d 5V and TA u003d 25 ° C.

Note 4: LTC485 design guarantees that its normal working voltage range on the power supply is 5V ± 10%. The data table parameter guarantees the test power supply range of 5V ± 5%.

典型性能特征

[123 ] Application

Basic theory of computing

The previous RS485 transceiver used bipolar technology because the co -mode range equipment must be extended to the supplier and equipment. Electricity damage and atresses must be immunized. Unfortunately, bipolar devices need a large amount of power current, which is unacceptable to many applications that require low power consumption. LTC485 is the first CMOS RS485/RS422 transceiver ultra -low power consumption, without sacrificing ESD and atresia immunity. The LTC485 uses a dedicated driver output level to allow the common modular range to expand to the power supply. At the same time, it almost eliminates the atresia and provides excellent electrostatic protection. Figure 9 shows the LTC485 output stage, and Figure 10 shows the traditional CMOS output stage. When the traditional CMOS output stage is shown in Figure 10 to enter the high impedance state, the two P channel (P1) N channel (N1) are closed. If the output is the P+/N -trap diode (D1) or the N+/P substrate diode (D2) above the VCC or underground driver (D1) or the N+/P substrate diode (D2), the output is restrained on the power supply. Therefore, the output level is no longer in high impedance state and cannot meet the requirements of the RS485 co -mode range. In addition, a large number of current flows can produce a well -known CMOS atresia through any diode, which may damage the device. The LTC485 output level in Figure 9 eliminates these problems to increase the problems of the two Schottky diode, SD3 and SD4. The Schottky diodes are improved by patent improvement through the standard N -trap CMOS process. When the output -level work is normal, the Schottky diode is positive, and a small voltage is lowered through them. When the output is in a high impedance state, the driving voltage is higher than VCC or lower than the ground, and the parasite diode D1 or D2 is still open, but SD3 or SD4 will be reversedShooting and preventing current from flowing into N wells or under wells. Therefore, the high impedance state keeps the output voltage exceeding the power supply. There are no small load current flowing into the N-trap or sub-strategy, and the lock is actually in power or power off.

Application

LTC485 output stage will remain high until the N channel or P channel failure is reached when it is positive or negative, respectively. This output will be stabbed to VCC or the grounding voltage of Zina plus the Schottky diode, but this voltage is beyond the range of RS485. This clip protects the ESD voltage of the MOS grid is much higher than 2000V. Because the current injected by electrostatic discharge is composed of most carriers on the N -trap or substrate, the lock is a careful layout technique. Many digital encoding schemes delay delayed delayed dependence on drivers and recipients. The test circuit 12 in Figure 13 and 11 shows the typical LTC485 receiver transmission delay. The delay time of the receiver is: #63718; TPLH -TPHL #63718; u003d 9NS typical value, VCC u003d 5V driver deviation time is: tilt u003d 5ns typical value, VCC u003d 5V maximum 10ns, VCC u003d 5V, TA u003d --40 ° C to 85 ° C

Application

LTC485 line length and data rate RS422/RS485's maximum line length standard is 4,000 feet.

Use the test circuit in Figure 14, Figure 15 and 16 show ~ 20VP-P co-model noise injection cable, LTC485 can be at the end of the twisted twisted end of 4,000 feet Essence

Figures 17 and 18 Display LTC485 can easily drive 4000 feet long wires at a frequency of 110kHz

as specified as specified The curve in Figure 19 should be used when the governor and maximum data rate:

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