LINER LTC1520CS

Final Electrical Specifications
LTC1520
50Mbps Precision Quad
Line Receiver
U
DESCRIPTION
FEATURES
■
■
■
■
■
■
■
■
■
■
■
■
Precision Propagation Delay: 18ns ±3ns Over
Temperature
Data Rate: 50Mbps
Low tPLH/tPHL Skew: 500ps Typ
Low Channel-to-Channel Skew: 400ps Typ
Rail-to-Rail Input Common Mode Range
High Input Resistance: ≥ 18k, Even When Unpowered
Hot Swap Capable
Can Withstand Input DC Levels of ±10V
Short-Circuit Protected
Single 5V Supply
LVDS Compatible
Will Not Oscillate with Slow Input Signals
U
APPLICATIONS
■
■
■
■
■
■
May 1996
The LTC®1520 is a high speed, precision differential line
receiver that can operate at data rates as high as 50Mbps.
A unique architecture provides very stable propagation
delays and low skew over a wide input common mode,
input overdrive and ambient temperature range. Propagation delay is 18ns ±3ns, while typically tPLH/tPHL skew is
500ps and channel-to-channel skew is 400ps.
Each receiver translates differential input levels (VID ≥
100mV) into valid CMOS and TTL output levels. Its high
input resistance (≥18k) allows many receivers to be connected to the same driver. The receiver outputs go into a
high impedance state when disabled.
Protection features include thermal shutdown and a controlled maximum short-circuit current (50mA max) that
does not oscillate in and out of short-circuit mode. Input
resistance remains ≥18k when the device is unpowered or
disabled, thus allowing the LTC1520 to be hot swapped into
a backplane without loading the data lines.
High Speed Backplane Interface
Line Collision Detector
PECL and LVDS Line Receivers
Level Translator
Ring Oscillator
Tapped Delay Line
The LTC1520 operates from a single 5V supply and draws
12mA of supply current. The part is available in a 16-lead
narrow SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATION
High Speed Backplane Receiver
Propagation Delay Guaranteed to Fall
Within Shaded Area (±3ns)
LTC1520
+
+
–
–
RECEIVER
INPUT
VID = 500mV
VIN =
1V/DIV
+
RECEIVER
OUTPUT
VDD = 5V
VOUT =
5V/DIV
–
+
–
5V
–5
3.3k
0
5
10 15 20 25 30 35 40 45
TIME (ns)
LTC1520 TA02
3.3k
0.01µF
LTC1520 TA01
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.
1
LTC1520
U
U
RATI GS
W
W W
W
AXI U
U
ABSOLUTE
PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage ....................................................... 10V
Digital Input Currents ..................... – 100mA to 100mA
Digital Input Voltages ............................... – 0.5V to 10V
Receiver Input Voltages ........................................ ±10V
Receiver Output Voltages ............. – 0.5V to VDD + 0.5V
Short-Circuit Duration .................................... Indefinite
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
TOP VIEW
B1 1
16 VDD
A1 2
15 B4
OUT 1 3
14 A4
LTC1520CS
13 OUT 4
ENABLE 4
12 NC
OUT 2 5
A2 6
11 OUT 3
B2 7
10 A3
9
GND 8
B3
S PACKAGE
16-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 90°C/ W
Consult factory for Industrial and Military grade parts.
DC ELECTRICAL CHARACTERISTICS
VDD = 5V (Notes 2, 3) per receiver, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VCM
Input Common Mode Voltage
A, B Inputs
●
– 0.2
MIN
VIH
Input High Voltage
Enable Input
●
2
VIL
Input Low Voltage
Enable Input
●
IIN1
Input Current
Enable Input
●
–1
IIN2
Input Current (A, B)
VA, VB = 5V
VA, VB = 0
●
●
– 0.2V ≤ VCM ≤ VDD + 0.2V
●
MAX
VDD + 0.2
UNITS
V
V
0.8
V
1
µA
250
– 250
µA
µA
18
kΩ
RIN
Input Resistance (Figure 5)
CIN
A, B Input Capacitance
VOC
Open-Circuit Input Voltage (Figure 5)
VDD = 5V (Note 4)
●
3.2
VID(MIN)
Differential Input Threshold Voltage
– 0.2V < VCM < VDD + 0.2V
●
– 0.1
dVID
Input Hysteresis
VCM = 2.5V
●
VOH
Output High Voltage
IOUT = – 4mA, VID = 0.1V, VDD = 5V
●
VOL
Output Low Voltage
IOUT = 4mA, VID = 0.1V, VDD = 5V
●
IOZR
Three-State Output Current
0V ≤ VOUT ≤ 5V
●
IDD
Total Supply Current All 4 Receivers
VID ≥ 0.1V, No Load, Enable = 5V
●
IOSR
Short-Circuit Current
VOUT = 0V, VOUT = 5V
●
CMRR
Common Mode Rejection Ratio
VCM = 2.5V, f = 25MHz
2
TYP
3
3.3
pF
3.4
V
0.1
V
20
mV
4.6
V
– 10
12
– 50
45
0.4
V
10
µA
20
mA
50
mA
dB
LTC1520
U
W
SWITCHI G TI E CHARACTERISTICS
VDD = 5V (Notes 2, 3) VID = 500mV, VCM = 2.5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tPLH, tPHL
Input-to-Output Propagation Delay
CL = 15pF (Figure 1)
tr, tf
Rise/Fall Times
CL = 15pF
tSKD
tPLH – tPHL Skew
CL = 15pF, Same Receiver (Note 5)
tZL
Enable to Output Low
tZH
Enable to Output High
tLZ
Disable from Output Low
tHZ
tCH-CH
tPKG-PKG
fIN
MIN
●
15
TYP
MAX
18
21
UNITS
ns
2.5
ns
●
500
ps
CL = 15pF (Figure 2)
●
10
25
ns
CL = 15pF (Figure 2)
●
10
25
ns
CL = 15pF (Figure 2)
●
20
35
ns
Disable from Output High
CL = 15pF (Figure 2)
●
20
35
ns
Channel-to-Channel Skew
CL = 15pF (Figure 3) (Note 6)
●
400
ps
Package-to-Package Skew
CL = 15pF, Same Temperature
(Figure 4, Note 4)
1.5
ns
Minimum Input Pulse Width
(Note 4)
12
ns
Maximum Input Frequency
(Note 4)
40
MHz
The ● denotes specifications which apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the
safety of the device cannot be guaranteed. Recommended: VDD = 5V ±5%.
Note 2: All currents into the device pins are positive; all currents out of the
device pins are negative.
Note 3: All typicals are given for VDD = 5V, TA = 25°C.
Note 4: Guaranteed by design, but not tested.
Note 5: Worst-case tPLH – tPHL skew for a single receiver in a package
over the full operating temperature range.
Note 6: Maximum difference between any two tPLH or tPHL transitions in a
single package over the full operating temperature range.
U W
TYPICAL PERFORMANCE CHARACTERISTICS
Propagation Delay (tPLH/tPHL)
vs Input Overdrive
Propagation Delay (tPLH/tPHL)
vs Temperature
25
25
TA = 25°C
VCM = 2.5V
20
PROPAGATION DELAY (ns)
PROPAGATION DELAY (ns)
VCM = 2.5V
VID = 500mV
15
10
5
0
–50 –25
50
0
75
25
TEMPERATURE (°C)
100
125
LTC1520 G01
20
15
10
5
0
0.05
0.1
1
INPUT OVERDRIVE (V)
5
10
1520 G02
3
LTC1520
U W
TYPICAL PERFORMANCE CHARACTERISTICS
Propagation Delay (tPLH/tPHL)
vs Input Common Mode
CMRR vs Frequency
25
46.5
COMMON MODE REJECTION RATIO (dB)
PROPAGATION DELAY (ns)
TA = 25°C
VID = 500mV
20
15
10
5
0
46.0
45.5
45.0
44.5
44.0
43.5
43.0
42.5
TA = 25°C
42.0
0
4
1
3
2
INPUT COMMON MODE (V)
5
1k
10
100k
FREQUENCY (Hz)
LTC1520 G03
10M
LTC1520 G04
U
U
U
PIN FUNCTIONS
B1 (Pin 1): Receiver 1 Inverting Input.
B3 (Pin 9): Receiver 3 Inverting Input.
A1 (Pin 2): Receiver 1 Noninverting Input.
A3 (Pin 10): Receiver 3 Noninverting Input.
RO1 (Pin 3): Receiver 1 Output.
RO3 (Pin 11): Receiver 3 Output.
Enable (Pin 4): Receiver Output Enable Pin. A logic high
input enables the receiver outputs. A logic low input
forces the receiver outputs into a high impedance state.
Do not float.
NC (Pin 12): No Connection.
RO2 (Pin 5): Receiver 2 Output.
B4 (Pin 15): Receiver 4 Inverting Input.
A2 (Pin 6): Receiver 2 Noninverting Input.
VDD (Pin 16): 5V Supply Pin. This pin should be decoupled
with a 0.1µF ceramic capacitor as close as possible to the
pin. Recommended: VDD = 5V ±5%.
B2 (Pin 7): Receiver 2 Inverting Input.
RO4 (Pin 13): Receiver 4 Output.
A4 (Pin 14): Receiver 4 Noninverting Input.
GND (Pin 8): Ground Pin. A ground plane is recommended
for all LTC1520 applications.
U
W
W
SWITCHI G TI E WAVEFOR S
3V
2.5V
INPUT
2.5V
OUTPUT
INPUT
2V
VDD/2
+
1/4 LTC1520
t PHL
t PLH
2.5V
VDD/2
–
OUTPUT
15pF
1520 F01b
1520 F01
Figure 1. Propagation Delay Test Circuit and Waveforms
4
LTC1520
U
W
W
SWITCHI G TI E WAVEFOR S
3V
3V
ENABLE
1.5V
1.5V
t ZL
t LZ
INPUT
A1, A2
0V
5V
OUT 1
OUTPUT
NORMALLY LOW
1.5V
VOL
CH1 OUT
0.2V
2V
B1, B2 = 2.5V
VDD/2
VDD/2
t CH-CH
VOH
OUT 1
0V
VDD/2
CH2 OUT
0.2V
OUTPUT
NORMALLY HIGH
1.5V
t CH-CH
VDD/2
1520 F03
t HZ
t ZH
Figure 3. Any Channel to Any Channel Skew, Same Package
S1
1k
RECEIVER
OUTPUT
VDD
CL
1k
S2
1520 F02
INPUT
A1, B1
VID = 500mV
SAME INPUT FOR BOTH PACKAGES
Figure 2. Receiver Enable and Disable Timing
Test Circuit and Waveforms
PACKAGE 1
OUT 1
t PKG-PKG
tPKG-PKG
PACKAGE 2
OUT 1
1520 F04
Figure 4. Package-to-Package Propagation Delay Skew
U U
EQUIVALE T I PUT NETWORKS
≥18k
≥18k
A
3.3V
A
≥18k
≥18k
B
3.3V
RECEIVER ENABLED, VDD = 5V
B
RECEIVER DISABLED OR VDD = 0V
1520 F05
Figure 5. Input Thevenin Equivalent
U
W
U
U
APPLICATIONS INFORMATION
Theory of Operation
Unlike typical line receivers whose propagation delay can
vary by as much as 500% from package to package and
show significant temperature drift, the LTC1520 employs
a novel architecture that produces a tightly controlled and
temperature compensated propagation delay. The differential timing skew is also minimized between rising and
falling output edges, and the propagation delays of any
two receivers within a package are very tightly matched.
The precision timing features of the LTC1520 reduce
overall system timing constraints by providing a narrow
6ns window during which valid data appears at the receiver output. This output timing window applies to all
receivers in all packages over all operating temperatures
5
LTC1520
U
U
W
U
APPLICATIONS INFORMATION
thereby making the LTC1520 well suited for high speed
parallel data transmission applications such as backplanes.
In clocked data systems, the low skew minimizes duty
cycle distortion of the clock signal. The LTC1520 can
propagate signals at frequencies up to 25MHz (50Mbps)
with less than 5% duty cycle distortion. When a clock
signal is used to retime parallel data, the maximum recommended data transmission rate is 25Mbps to avoid timing
errors due to clock distortion.
PC traces. Note that at very high speeds, transmission line
and driver ringing effects have to be considered. Motorola’s
MECL System Design Handbook serves as an excellent
reference for transmission line and termination effects. To
mitigate transmission errors and duty cycle distortion due
to driver ringing, a small output filter or a dampening
resistor on VDD may be needed as shown in Figure 6b. To
transmit single-ended data over distances up to 10 feet,
twisted pair is recommended with the unused wire
grounded at both ends (Figure 7).
Rail-to-rail input common mode range enables the LTC1520
to be used in both single-ended and differential applications with transmission distances up to 100 feet. Thermal
shutdown and short-circuit protection prevent latchup
damage to the LTC1520 during fault conditions.
MC74ACT04
MC74AC04
10-FT TWISTED PAIR
–
120Ω
5V
Single-Ended Applications
3.3k
Over short distances, the LTC1520 can be configured to
receive single-ended data by tying one input to a fixed bias
voltage and connecting the other input to the driver output.
In such applications, standard high speed CMOS logic
may be used as a driver for the LTC1520. The receiver trip
points may be easily adjusted to accommodate different
driver output swings by changing the resistor divider at the
fixed input. Figure 6a shows a single-ended receiver
configuration with the driver and receiver connected via
MC74ACT04
(TTL INPUT)
PC TRACE
–
5V
1/4 LTC1520
MC74AC04
(CMOS INPUT)
2.2k
0.01µF
1/4 LTC1520
+
+
2.2k
0.01µF
2.2k
1520 F07
Figure 7. Medium Distance Single-Ended Transmission
Using a CMOS Driver
Differential Transmission
The LTC1520 is well suited for medium distance differential transmission due to its rail-to-rail input common mode
range. Clock rates up to 25MHz can be transmitted over
100 feet of high quality twisted pair. Figure 8 shows the
LTC1520 receiving differential data from a PECL driver. As
in the single-ended configurations, care must be taken to
properly terminate the differential data lines to avoid
unwanted reflections, etc.
1520 F06a
5V
Figure 6a. Single-Ended Receiver
100Ω
5V
100-FT TWISTED PAIR
100Ω
5V
10Ω
MC74AC04
*
0.01µF
100Ω
10Ω
PC TRACE
OR
PC TRACE
100Ω
10pF
+
RT
1/4 LTC1520
120Ω
–
*MC10116
1520 F06b
Figure 6b. Techniques to Minimize Driver Ringing
6
1520 F08
Figure 8. Differential Transmission Over Long Distances
LTC1520
U
U
W
U
APPLICATIONS INFORMATION
Alternate Uses
The tightly controlled propagation delay of the LTC1520
allows the part to serve as a fixed delay element. Figure 9
shows the LTC1520 used as a tapped delay line with 18ns
±3ns steps. Several LTC1520s may be connected in series
to form longer delay lines. Each tap in the delay line is
accurate to within ±17% over temperature.
As shown in Figure 10, the LTC1520 can be used to create
a temperature stable ring oscillator with period increments
of 36ns. Low skew and good channel-to-channel matching enable this oscillator to achieve better than a 45/55
duty cycle (the duty cycle approaches 50/50 as more
LTC1520s are used for lower frequencies). Note that the
fixed voltage bias may either be created externally with a
resistor divider or generated internally using a bypass
capacitor and the internal open circuit bias point (approximately 3.3V). The use of the internal bias point will result
in a 1% to 2% distortion of the duty cycle.
0ns DELAY
18ns DELAY
+
INPUT
36ns DELAY
1/4 LTC1520
+
–
1/4 LTC1520
+
–
1/4 LTC1520
+
–
1/4 LTC1520
5V
54ns DELAY
3.3k
0.01µF
72ns DELAY
–
3.3k
1520 F09
Figure 9. Tapped Delay Line with 18ns Steps
5V
3.3k
0.01µF
3.3k
+
+
1/4 LTC1520
1/4 LTC1520
–
9.3MHz OSCILLATOR
WITH BETTER THAN
45/55 DUTY CYCLE
–
+
1/4 LTC1520
–
0.01µF
TYPICAL STABILITY
± 5% OVER TEMPERATURE
+
+
+
1/4 LTC1520
1/4 LTC1520
1/4 LTC1520
–
–
6.9MHz
OSCILLATOR OUTPUT
–
+
1/4 LTC1520
–
1520 F10
Figure 10. Temperature Stable Ring Oscillators
7
LTC1520
U
PACKAGE DESCRIPTION
S Package
16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.386 – 0.394*
(9.804 – 10.008)
16
15
14
13
12
11
10
9
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
2
3
4
5
6
7
8
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0° – 8° TYP
0.016 – 0.050
0.406 – 1.270
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
0.050
(1.270)
TYP
0.014 – 0.019
(0.355 – 0.483)
S16 0695
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC486/487
Low Power Quad RS485 Driver
10Mbps, – 7V to 12V Common Mode Range
LTC488/489
Low Power Quad RS485 Receiver
10Mbps, – 7V to 12V Common Mode Range
LT 1016
Ultrafast Precision Comparator
Single 5V Supply, 10ns Propagation Delay
LTC1518
High Speed Quad RS485 Receiver
50Mbps, – 7V to 12V Common Mode Range
LTC1519
High Speed Quad RS485 Receiver
50Mbps, – 7V to 12V Common Mode Range
®
8
Linear Technology Corporation
LT/GP 0596 6K • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1996