Datasheet

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LTC486

486fc

TYPICAL APPLICATION

DESCRIPTION

Quad Low Power

RS485 Driver

The LTC

486 is a low power differential bus/line driver

designed for multipoint data transmission standard RS485

applications with extended common-mode range (12V to

–7V). It also meets RS422 requirements.

The CMOS design offers signiﬁcant power savings over

its bipolar counterpart without sacriﬁcing ruggedness

against overload or ESD damage.

The driver features three-state outputs, with the driver

outputs maintaining high impedance over the entire

common-mode range. Excessive power dissipation caused

by bus contention or faults is prevented by a thermal

shutdown circuit which forces the driver outputs into a

high impedance state.

Both AC and DC speciﬁcations are guaranteed from 0°C

to 70°C (Commercial), –40°C to 85°C (Industrial), over

the 4.75V to 5.25V supply voltage range.

RS485 Length Speciﬁcation

FEATURES

APPLICATIONS

Very Low Power: I

= 110µA Typ

Designed for RS485 or RS422 Applications

Single 5V Supply

–7V to 12V Bus Common-Mode Range Permits ±7V

GND Difference Between Devices on the Bus

Thermal Shutdown Protection

Power-Up/Down Glitch-Free Driver Outputs Permit

Live Insertion/Removal of Package

Driver Maintains High Impedance in Three-State or

with the Power Off

28ns Typical Driver Propagation Delays with 5ns

Skew

Pin Compatible with the SN75172, DS96172,

µA96172, and DS96F172

Low Power RS485/RS422 Drivers

Level Translator

486 TA01a

RECEIVER

4 4

1/4 LTC486

120Ω

1/4 LTC488

4000 FT BELDEN 9841

DRIVER

DATA RATE (bps)

10k

* APPLIES FOR 24 GAUGE, POLYETHYLENE

DIELECTRIC TWISTED PAIR

CABLE LENGTH (FT)

100

10k

100k 1M 10M

486 TA01b

2.5M

L, LT, LTC, LTM, Linear Technology, µModule and the Linear logo are registered trademarks of

Linear Technology Corporation. All other trademarks are the property of their respective owners.

Summary of content (14 pages)

PAGE 1
LTC486 Quad Low Power RS485 Driver FEATURES n n n n n n n n n DESCRIPTION Very Low Power: ICC = 110µA Typ Designed for RS485 or RS422 Applications Single 5V Supply –7V to 12V Bus Common-Mode Range Permits ±7V GND Difference Between Devices on the Bus Thermal Shutdown Protection Power-Up/Down Glitch-Free Driver Outputs Permit Live Insertion/Removal of Package Driver Maintains High Impedance in Three-State or with the Power Off 28ns Typical Driver Propagation Delays with 5ns Skew Pin Compatible with the
PAGE 2
LTC486 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage (VCC).................................................12V Control Input Voltages........................0.5V to VCC + 0.5V Driver Input Voltages....................... –0.5V to VCC + 0.5V Driver Output Voltages.............................................±14V Control Input Currents..........................................±25mA Driver Input Currents............................................
PAGE 3
LTC486 DC ELECTRICAL CHARACTERISTICS VCC = 5V ±5%, 0°C ≤ Temperature ≤ 70°C (Commercial), –40°C ≤ Temperature ≤ 85°C (Industrial) (Notes 2, 3) SYMBOL PARAMETER CONDITIONS MIN VOD1 Differential Driver Output Voltage (Unloaded) IOUT = 0 VOD2 Differential Driver Output Voltage (With Load) R = 50Ω; (RS422) Change in Magnitude of Driver Differential Output Voltage for Complementary Output States VOC Driver Common-Mode Output Voltage |VOC| Change in Magnitude of Driver Common-Mode Output Voltage fo
PAGE 4
LTC486 SWITCHING TIME WAVEFORMS DI 3V f = 1MHz : t r < 10ns : t f < 10ns 1.5V 0V t PLH B A VO –VO 1.5V t PHL VO t SKEW 1/2 VO 80% t SKEW 1/2 VO 90% VDIFF = V(A) – V(B) 10% 20% tf tr 486 F01 Figure 1. Driver Propagation Delays EN 3V f = 1MHz : t r ≤ 10ns : t f ≤ 10ns 1.5V 0V 5V A, B VOL t ZL VOH A, B 0V 1.5V t LZ 2.3V OUTPUT NORMALLY LOW 2.3V OUTPUT NORMALLY HIGH 0.5V 0.5V tHZ tZH 486 F02 Figure 2.
PAGE 5
LTC486 TYPICAL PERFORMANCE CHARACTERISTICS Driver Output High Voltage vs Output Current TA = 25°C Driver Differential Output Voltage vs Output Current TA = 25°C 64 –48 –24 1 2 3 48 32 16 0 4 OUTPUT VOLTAGE (V) 0 1 2 3 486 G01 60 40 20 0 4 OUTPUT VOLTAGE (V) TTL Input Threshold vs Temperature 0 1 2 3 OUTPUT VOLTAGE (V) 486 G02 4 486 G03 Driver Skew vs Temperature 1.63 5 1.61 4 TIME (ns) INPUT THRESHOLD VOLTAGE (V) 1.59 3 2 1.57 1.
PAGE 6
LTC486 FUNCTION TABLE INPUT ENABLES OUTPUTS DI EN EN OUTA OUTB H L H L X H H X X L X X L L H H L H L Z L H L H Z H: High Level L: Low Level X: Irrelevant Z: High Impedance (Off) PIN FUNCTIONS DI1 (Pin 1): Driver 1 Input. If Driver 1 is enabled, then a low on DI1 forces the driver outputs DO1A low and DO1B high. A high on DI1 with the driver outputs enabled will force DO1A high and DO1B low. GND (Pin 8): Ground Connection. DO1A (Pin 2): Driver 1 Output. DO3B (Pin 11): Driver 3 Output.
PAGE 7
LTC486 TEST CIRCUITS A R VOD R B VOC 486 F03 Figure 3. Driver DC Test Load EN CI1 A DI DRIVER RDIFF B CI2 486 F04 EN Figure 4. Driver Timing Test Circuit S1 VCC OUTPUT UNDER TEST 500Ω CL S2 486 F05 Figure 5.
PAGE 8
LTC486 APPLICATIONS INFORMATION EN EN 4 DX 1 SHIELD SHIELD 3 2 120Ω DX 120Ω 4 3 RX 2 RX 1 12 12 EN 1/4 LTC486 DX 1 EN EN 4 4 3 1 DX EN 1/4 LTC488 3 RX 2 2 12 EN 1/4 LTC486 RX 12 EN 1/4 LTC488 486 F06 Figure 6. Typical Connection Typical Application Cable and Data Rate A typical connection of the LTC486 is shown in Figure 6. A twisted pair of wires connect up to 32 drivers and receivers for half duplex data transmission.
PAGE 9
LTC486 APPLICATIONS INFORMATION When using low loss cables, Figure 8 can be used as a guideline for choosing the maximum line length for a given data rate. With lower quality PVC cables, the dielectric loss factor can be 1000 times worse. PVC twisted pairs have terrible losses at high data rates (>100kbs) and greatly reduce the maximum cable length. At low data rates however, they are acceptable and much more economical. CABLE LENGTH (FT) 10k 1k 100 Cable Termination 10 10k 100k 1M 2.
PAGE 10
LTC486 APPLICATIONS INFORMATION The coupling capacitor allows high frequency energy to flow to the termination, but blocks DC and low frequencies. The dividing line between high and low frequency depends on the length of the cable. The coupling capacitor must pass frequencies above the point where the line represents an electrical one-tenth wavelength. The value of the coupling capacitor should therefore be set at 16.3pF per foot of cable length for 120Ω cables.
PAGE 11
LTC486 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. N Package 16-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510 Rev I) .770* (19.558) MAX 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 .255 ±.015* (6.477 ±0.381) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 +0.889 8.255 –0.381 NOTE: 1. DIMENSIONS ARE ) .130 ±.005 (3.302 ±0.127) .045 – .065 (1.143 – 1.651) .020 (0.
PAGE 12
LTC486 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. SW Package 16-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) .050 BSC .045 ±.005 .030 ±.005 TYP .398 – .413 (10.109 – 10.490) NOTE 4 16 N 15 14 13 12 11 10 9 N .325 ±.005 .420 MIN .394 – .419 (10.007 – 10.643) NOTE 3 1 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .005 (0.127) RAD MIN .009 – .013 (0.229 – 0.330) NOTE: 1.
PAGE 13
LTC486 REVISION HISTORY (Revision history begins at Rev C) REV DATE DESCRIPTION C 11/12 Order Information: corrected Package Descriptions PAGE NUMBER 2 Added Related Parts section 14 486fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 14
LTC486 TYPICAL APPLICATION RS232 to RS485 Level Translator with Hysteresis R = 220k Y 10k RS232 IN 120Ω DRIVER 5.