LTC1688/LTC1689
100Mbps RS485
Hot Swapable Quad Drivers
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
Ultrahigh Speed:
100Mbps
Guaranteed Propagation Delay: 8ns
±
4ns
Over Temperature
Low Channel-to-Channel Skew: 500ps Typ
Hot Swap
TM
Capable
50Mbps Operation with V
DD
= 3V
Low t
PLH
/t
PHL
Skew: 500ps Typ
Driver Outputs Maintain High Impedance in
Three-State or with Power Off
Short-Circuit Protected: 3mA Typ Output Current
for an Indefinite Short
Thermal Shutdown Protected
Single 5V or 3V Supply
Pin Compatible with LTC486/LTC487
The LTC
®
1688/LTC1689 are ultrahigh speed, differential
bus/line drivers that can operate at data rates up to
100Mbps. Propagation delay is guaranteed at 8ns
±4ns
over the full operating temperature range. These devices
operate over the full RS485 common mode range (– 7V
to 12V), and also meet RS422 requirements.
The driver outputs are Hot Swap capable, maintaining
backplane data integrity during board insertion and
removal. The drivers feature three-state outputs, maintain-
ing high impedance over the entire common mode range
(– 7V to 12V). Outputs also remain high impedance during
power-up and with the power off. A short-circuit feature
detects bus contention and substantially reduces driver
output current. Thermal shutdown circuitry protects the
parts from excessive power dissipation.
The LTC1688 allows all four drivers to be enabled together,
while the LTC1689 allows two drivers at a time to be
enabled.
The LTC1688/LTC1689 operate from a single 5V or 3V
supply and draw only 9mA of supply current.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
High Speed RS485 Twisted-Pair Drivers
High Speed Backplane Drivers
Complementary Clock Drivers
STS-1/OC-1 Data Drivers
SCSI Drivers
TYPICAL APPLICATIO
50Mbps RS485 Data Connection
2V/DIV
DRIVER
100Ω
100Ω
2V/DIV
RECEIVER
2V/DIV
100 FT CATEGORY 5 UTP
1/4 LTC1688
1/4 LTC1518
1688/89 TA01
5V/DIV
U
20ns Pulse Across 100 Feet
of Category 5 UTP
DRIVER INPUT
DRIVER OUTPUTS
CABLE DELAY
RECEIVER INPUT
RECEIVER OUTPUT
20ns/DIV
1688/89 TA02
U
U
16889fa
1
LTC1688/LTC1689
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
DI1 1
DO1A 2
DO1B 3
EN (EN12*) 4
DO2B 5
DO2A 6
DI2 7
GND 8
16 V
DD
15 DI4
14 DO4A
13 DO4B
12 ENB (EN34*)
11 DO3B
10 DO3A
9
DI3
Supply Voltage (V
DD
) ................................................ 7V
Enable Input Voltages ................. – 0.5V to (V
DD
+ 0.5V)
Enable Input Currents ..................... – 100mA to 100mA
Driver Input Voltages .................. – 0.5V to (V
DD
+ 0.5V)
Driver Output Voltages ................. (– 12V + V
DD
) to 12V
Driver Input Currents ...................... – 100mA to 100mA
Short-Circuit Duration (V
OUT
: – 7V to 10V) ...... Indefinite
Operating Temperature Range
LTC1688C/LTC1689C ............................. 0°C to 70°C
LTC1688I/LTC1689I .......................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1688CS
LTC1689CS
LTC1688IS
LTC1689IS
S PACKAGE
16-LEAD PLASTIC SO
*LTC1689 ONLY
T
JMAX
= 150°C,
θ
JA
= 90°C/ W
Consult factory for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at T
A
= 25°C.
PARAMETER
Differential Driver Output (Unloaded)
Differential Driver Output (With Load)
Change in Magnitude of Driver Differential
Output Voltage for Complementary
Output States
Driver Common Mode Output Voltage
Change in Magnitude of Driver Common
Mode Output Voltage for Complementary
Output States
Input High Voltage
Input Low Voltage
Input Current
Three-State (High Impedance)
Output Current
Supply Current of Entire Device
Driver Short-Circuit Current, V
OUT
= HIGH
Driver Short-Circuit Current, V
OUT
= LOW
Differential Driver Output (Unloaded)
Differential Driver Output (With Load)
Change in Magnitude of Driver Differential
Output Voltage for Complementary
Output States
Driver Common Mode Output Voltage
SYMBOL
V
OD1
V
OD2
∆V
OD
CONDITIONS
I
OUT
= 0
V
DD
= 5V, Per Driver, T
A
= 25
°
C, Unless Otherwise Noted (Note 2)
The
q
denotes the specifications which apply over the full operating
MIN
q
q
q
q
TYP
MAX
V
DD
UNITS
V
V
V
V
R = 50Ω (RS422)
R = 25Ω (RS485), Figure 1
R = 25Ω or 50Ω, Figure 1
2
1.5
3.0
0.2
V
OC
∆V
OC
R = 25Ω or 50Ω, Figure 1
R = 25Ω or 50Ω, Figure 1
q
q
2
3
0.2
V
IH
V
IL
I
IN1
I
OZ
I
DD
I
OSD1
I
OSD2
V
OD1
V
OD2
∆V
OD
EN, ENB, EN12, EN34, DI
EN, ENB, EN12, EN34, DI
EN, ENB, EN12, EN34, DI
V
OUT
= – 7V to 12V
No Load, Digital Input Pins = 0V or V
DD
V
OUT
= – 7V to 10V
V
OUT
= – 7V to 10V
I
OUT
= 0
R = 50Ω (RS422)
R = 25Ω (RS485), Figure 1
R = 25Ω or 50Ω, Figure 1
q
q
q
q
q
q
q
2
0.8
±1
±2
9
±200
18
±
20
±
20
V
DD
= 3V, Per Driver, T
A
= 25
°
C, Unless Otherwise Noted (Note 2)
q
V
DD
1.5
0.65
0.1
2.0
q
V
OC
R = 25Ω or 50Ω, Figure 1
1.3
16889fa
2
U
V
V
V
V
µA
µA
mA
mA
mA
V
V
V
V
V
W
U
U
W W
W
LTC1688/LTC1689
DC ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at T
A
= 25°C.
SYMBOL
∆V
OC
PARAMETER
Change in Magnitude of Driver Common
Mode Output Voltage for Complementary
Output States
Input High Voltage
Input Low Voltage
Input Current
Three-State (High Impedance)
Output Current
Supply Current of Entire Device
Driver Short-Circuit Current, V
OUT
= HIGH
Driver Short-Circuit Current, V
OUT
= LOW
CONDITIONS
The
q
denotes the specifications which apply over the full operating
MIN
TYP
0.1
MAX
UNITS
V
R = 25Ω or 50Ω, Figure 1
V
IH
V
IL
I
IN1
I
OZ
I
DD
I
OSD1
I
OSD2
EN, ENB, EN12, EN34, DI
EN, ENB, EN12, EN34, DI
EN, ENB, EN12, EN34, DI (Note 3)
V
OUT
= – 7V to 10V (Note 3)
No Load, Digital Input Pins = 0V or V
DD
V
OUT
= – 7V to 8V (Note 3)
V
OUT
= – 7V to 8V (Note 3)
q
q
q
q
1.4
0.5
±1
±1
5
±200
V
V
µA
µA
mA
±20
±20
mA
mA
q
q
SWITCHING CHARACTERISTICS
SYMBOL
t
PLH
, t
PHL
t
SKEW
t
r
, t
f
t
ZH
t
ZL
t
LZ
t
HZ
C
L(MAX)
PARAMETER
Driver Input-to-Output Propagation Delay
Driver Output-to-Output Skew
Driver Rise/Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable from Low
Driver Disable from High
Maximum Output Capacitive Load
Maximum Data Rate
Maximum Driver Input Rise/Fall Time
V
DD
= 3V, T
A
= 25
°
C, Unless Otherwise Noted (Note 2)
t
PLH
, t
PHL
t
SKEW
t
r
, t
f
t
ZH
t
ZL
t
LZ
t
HZ
C
L(MAX)
Driver Input-to-Output Propagation Delay
Driver Output-to-Output Skew
Driver Rise/Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable from Low
Driver Disable from High
Maximum Output Capacitive Load
Maximum Data Rate
Maximum Driver Input Rise/Fall Time
V
DD
= 5V, T
A
= 25
°
C, Unless Otherwise Noted (Note 2)
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
CONDITIONS
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
C
L
= 25pF, S2 Closed, Figures 3, 5
C
L
= 25pF, S1 Closed, Figures 3, 5
C
L
= 15pF, S1 Closed, Figures 3, 5
C
L
= 15pF, S2 Closed, Figures 3, 5
(Note 3)
(Note 3)
(Note 3)
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
R
DIFF
= 50Ω, C
L1
= C
L2
= 25pF,
Figures 2, 4
C
L
= 25pF, S2 Closed, Figures 3, 5
C
L
= 25pF, S1 Closed, Figures 3, 5
C
L
= 15pF, S1 Closed, Figures 3, 5
C
L
= 15pF, S2 Closed, Figures 3, 5
(Note 3)
(Note 3)
q
q
q
q
q
q
q
q
q
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
U
MIN
4
TYP
8
500
2
10
10
25
25
MAX
12
UNITS
ns
ps
ns
35
35
65
65
200
ns
ns
ns
ns
pF
Mbps
ns
ns
ns
ns
ns
ns
ns
ns
100
500
11
1
4
25
25
50
50
200
50
500
pF
Mbps
ns
q
Note 2:
All currents into the device pins are positive; all currents out of the
device pins are negative.
Note 3:
Guaranteed by design or correlation, but not tested.
16889fa
3
LTC1688/LTC1689
TYPICAL PERFORMANCE CHARACTERISTICS
Propagation Delay
vs Temperature
14
12
V
DD
= 3V
PROPAGATION DELAY (ns)
PROPAGATION DELAY (ns)
10
8
6
4
2
0
0
20
40
60
80
TEMPERATURE (°C)
100
1688/89 G01
V
DI
= 0V TO 3V
R
DIFF
= 50Ω
C
L
= 25pF
Supply Current vs Data Rate
250
4.0
3.5
200
SUPPLY CURRENT (mA)
4 DRIVERS
SWITCHING
150
V
DD
= 5V
R
DIFF
= 50Ω, PER DRIVER
C
L
= 25pF, PER DRIVER
T
A
= 25°C
1 DRIVER
SWITCHING
OUTPUT CURRENT (µA)
100
50
0
0
20
40
60
80
DATA RATE (Mbps)
100
120
V
OD2
vs Temperature
2.5
180
160
2.0
V
DD
= 5V
140
120
I
DD
(mA)
1.5
V
OD2
1.0
0.5
R
DIFF
= 50Ω
0
0
20
40
60
80
TEMPERATURE (°C)
100
1688/89 G05
4
U W
Propagation Delay
vs Load Capacitance
14
12
10
8
6
4
2
0
0
10
20
30
40
50
LOAD CAPACITANCE (pF)
60
V
DI
= 0V TO 3V
R
DIFF
= 50Ω
T
A
= 25°C
V
DD
= 5V
V
DD
= 3V
V
DD
= 5V
1688/89 G02
Three-State Output Current
V
DD
= 5V
3.0
2.5
2.0
1.5
1.0
0.5
0
0
20
40
60
80
TEMPERATURE (°C)
100
1688/89 G04
V
OUT
= –7V
V
OUT
= 12V
1688/89 G03
I
DD
vs Temperature
4 DRIVERS LOADED
100
80
60
40
20
0
0
20
40
60
80
TEMPERATURE (°C)
100
1688/89 G06
V
DD
= 3V
1 DRIVER LOADED
V
DD
= 5V
R
DIFF
= 50Ω, PER DRIVER
0.1Mbps
16889fa
LTC1688/LTC1689
PIN FUNCTIONS
DI1 (Pin 1):
Driver 1 Input. Do not float.
DO1A (Pin 2):
Driver 1 Noninverting Output.
DO1B (Pin 3):
Driver 1 Inverting Output.
EN (Pin 4, LTC1688):
High True Enable Pin, enables all
four drivers. A low on Pin 4 and a high on Pin 12 will put
all driver outputs into a high impedance state. See
Function Tables for details. Do not float.
EN12 (Pin 4, LTC1689):
Enables Drivers 1 and 2. A low on
Pin 4 will put the outputs of drivers 1 and 2 into a high
impedance state. See Function Tables for details. Do not
float.
DO2B (Pin 5):
Driver 2 Inverting Output.
DO2A (Pin 6):
Driver 2 Noninverting Output.
DI2 (Pin 7):
Driver 2 Input. Do not float.
GND (Pin 8):
Ground Connection. A good ground plane is
recommended for all applications.
DI3 (Pin 9):
Driver 3 Input. Do not float.
DO3A (Pin 10):
Driver 3 Noninverting Output.
DO3B (Pin 11):
Driver 3 Inverting Output.
ENB (Pin 12, LTC1688):
Low True Enable Pin, enables all
four drivers. A low on Pin 4 and a high on Pin 12 will put
all driver outputs into a high impedance state. See
Function Tables for details. Do not float.
EN34 (Pin 12, LTC1689):
Enables Drivers 3 and 4. A low
on Pin 12 will put the outputs of drivers 3 and 4 into a high
impedance state. See Function Tables for details. Do not
float.
DO4B (Pin 13):
Driver 4 Inverting Output.
DO4A (Pin 14):
Driver 4 Noninverting Output.
DI4 (Pin 15):
Driver 4 Input. Do not float.
V
DD
(Pin 16):
Power Supply Input. This pin should be
bypassed with a 0.1µF ceramic capacitor as close to the
pin as possible. Recommended: V
DD
= 3V to 5.25V.
FU CTIO TABLES
LTC1688
INPUTS
DI
H
L
H
L
X
EN
H
H
X
X
L
ENB
X
X
L
L
H
OUTA
H
L
H
L
HI-Z
OUTPUTS
OUTB
L
H
L
H
HI-Z
DI
H
L
X
TEST CIRCUITS
EN (EN12)
A
R
V
OD
R
B
V
OC
1688/89 TC01
Figure 1. Driver DC Test Load
U
U
U
U
U
LTC1689
INPUTS
EN12/EN34
H
H
L
OUTA
H
L
HI-Z
OUTPUTS
OUTB
L
H
HI-Z
C
L1
A
DI
DRIVER
B
C
L2
1688/89 TC02
S1
V
DD
OUTPUT
UNDER TEST
500
Ω
R
DIFF
C
L
S2
ENB (EN34)
1688/89 TC03
Figure 2. Driver Timing Test Circuit
Figure 3. Driver Timing Test Load
16889fa
5
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