LTC1324
Single Supply LocalTalk
®
Transceiver
FEATURES
s
s
s
s
DESCRIPTION
The LTC
®
1324 is a single 5V line transceiver designed to
operate on Apple
®
LocalTalk networks. The driver features
a digitally selectable low slew rate mode for reduced EMI
emissions. The chip draws only 1mA quiescent current
when active and 1µA in shutdown. The differential driver
outputs three-state when disabled, during shutdown or
when the power is off. The driver outputs will maintain
high impedance even with output common mode voltages
beyond the power supply rails. Both the driver outputs and
receiver inputs are protected against ESD damage to
±10kV.
The LTC1324 is available in a 16-pin SO Wide package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Apple and LocalTalk are registered trademarks of Apple Computer, Inc.
s
s
s
Single Chip 5V LocalTalk Port
Low Power: I
CC
= 1mA Typ
Shutdown Pin Reduces I
CC
to 1µA Typ
Digitally Selectable Low Slew Rate Mode for
Reduced EMI Emmisions
Drivers Maintain High Impedance in Three-State or
with Power Off
Thermal Shutdown Protection
Drivers Are Short-Circuit Protected
APPLICATIONS
s
s
s
LocalTalk Peripherals
Notebook and Palmtop Computers
Battery-Powered Systems
TYPICAL APPLICATION
Typical LocalTalk Connection for Low EMI
5V
16
SLEW RATE CONTROL
DATA IN
TX ENABLE
SHUTDOWN
RX ENABLE
DATA OUT
2
3
4
5
6
7
8
9
1324 TA01
Waveform of Driver
12
LocalTalk
TRANSFORMER
120Ω
D
IN
5V/DIV
11
LTC1324
10
D
OUT
1V/DIV
U
U
U
TIME (0.5µs/DIV)
1324 TA02
1
LTC1324
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
NC 1
SR 2
TXD 3
TXDEN 4
SHDN 5
RXEN 6
RXO 7
GND 8
N PACKAGE
16-LEAD PDIP
RX
DX
Supply Voltage (V
CC
) ................................................ 7V
Input Voltage (Logic Inputs) ........ – 0.3V to (V
CC
+ 0.3V)
Input Voltage (Receiver Inputs) ............................
±1
5V
Driver Output Voltage (Forced) .............................
±15V
Driver 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
16 V
CC
15 TXDEN
14 RXEN
13 NC
12 TXD
–
11 TXD
+
10 RXD
–
9
RXD
+
ORDER PART
NUMBER
LTC1324CN
LTC1324CSW
SW PACKAGE
16-LEAD PLASTIC SO WIDE
T
JMAX
= 150°C,
θ
JA
= 110°C/ W (N)
T
JMAX
= 150°C,
θ
JA
= 150°C/ W (SW)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
Supplies
I
CC
Normal Operation Supply Current
Shutdown Supply Current
V
CC
= 5V, T
A
= 0°C to 70°C (Notes 2, 3), unless otherwise noted.
MIN
TYP
MAX
UNITS
CONDITIONS
No Load, SHDN = 0V, TXDEN = 0V, RXEN = 0V
No Load, SHDN = V
CC
q
q
1
1
±4.0
±2.0
0.2
3.0
2
10
Differential Driver
V
OD
∆V
OD
V
OC
I
SS
I
OZ
Differential Output Voltage
Change in Magnitude of Differential
Output Voltage
Differential Common Mode Output Voltage
Short-Circuit Current
Three-State Output Current
No Load
R
L
= 50Ω (Figure 1)
R
L
= 50Ω (Figure 1)
R
L
= 50Ω (Figure 1)
0V
≤
V
O
≤
5V
(TXDEN = V
CC
and TXDEN = GND) or
SHDN = V
CC
or Power Off, – 10V
≤
V
O
≤
10V
q
q
q
q
35
120
±2
250
±200
Logic Inputs
V
IH
V
IL
I
IN
I
DN
Receiver
R
IN
Input Resistance
Receiver Threshold Voltage
Receiver Input Hysteresis
V
OH
V
OL
I
SS
I
OZ
Output High Voltage
Output Low Voltage
Output Short-Circuit Current
Output Three-State Current
– 7V
≤
V
IN
≤
7V
– 7V
≤
V
CM
≤
7V
– 7V
≤
V
CM
≤
7V
I
O
= – 4mA
I
O
= 4mA
0V
≤
V
O
≤
5V
0V
≤
V
O
≤
5V, RXEN = V
CC
, RXEN = GND
q
q
q
q
q
Input High Voltage
Input Low Voltage
Input Current
Pull-Down Current
All Logic Input Pins
All Logic Input Pins
SHDN, TXDEN, RXDEN, V = 0V to V
CC
RXDEN, TXDEN, SR, V = 0V to V
CC
q
q
q
q
2.4
0.8
±1
15
±20
60
12
– 200
70
3.5
0.4
7
±2
85
±100
200
2
U
W
U
U
W W
W
mA
µA
V
V
V
V
mA
µA
V
V
µA
µA
kΩ
mV
mV
V
V
mA
µA
LTC1324
ELECTRICAL CHARACTERISTICS
SYMBOL
t
PLH
, t
PHL
PARAMETER
Driver Propagation Delay
Without Slew Rate Control
Driver Propagation Delay
with Slew Rate Control
Receiver Propagation Delay
t
SKEW
Driver Output to Output
Without Slew Rate Control
Driver Output to Output
with Slew Rate Control
t
r
, t
f
Driver Rise/Fall Time
Without Slew Rate Control
Driver Rise/Fall Time
with Slew Rate Control
t
Hdis
, t
Ldis
Driver Output Active to Disable
Without Slew Rate Control
Driver Output Active to Disable
with Slew Rate Control
Receiver Output Active to Disable
t
ENH
, t
ENL
Driver Enable to Output Active
Without Slew Rate Control
Driver Enable to Output Active
with Slew Rate Control
Receiver Enable to Output Active
Switching Characteristics
V
CC
= 5V, T
A
= 0°C to 70°C (Notes 2, 3), unless otherwise noted.
MIN
q
q
q
q
q
q
q
q
q
q
q
q
q
CONDITIONS
R
L
= 100Ω, C
L
= 100pF (Figures 2, 4)
SR = GND
R
L
= 100Ω, C
L
= 100pF (Figures 2, 4)
SR = V
CC
C
L
= 15pF (Figures 2, 6)
R
L
= 100Ω, C
L
= 100pF (Figures 2, 4)
SR = GND
R
L
= 100Ω, C
L
= 100pF (Figures 2, 4)
SR = V
CC
R
L
= 100Ω, C
L
= 100pF (Figures 2,4)
SR = GND
R
L
= 100Ω, C
L
= 100pF (Figures 2, 4)
SR = V
CC
C
L
= 15pF (Figures 3, 5)
SR = GND
C
L
= 15pF (Figures 3, 5)
SR = V
CC
C
L
= 15pF (Figures 3, 7)
C
L
= 15pF (Figures 3, 5)
SR = GND
C
L
= 15pF (Figures 3, 5)
SR = V
CC
C
L
= 15pF (Figures 3, 7)
TYP
40
0.4
40
10
25
20
0.4
50
0.7
30
50
250
30
MAX
120
1.2
120
35
100
50
1.2
150
2
100
150
750
100
UNITS
ns
µs
ns
ns
ns
ns
µs
ns
µs
ns
ns
ns
ns
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All currents into device pins are positive and all currents out of
device pins are negative. All voltages are reference to ground unless
otherwise specified.
Note 3:
All typicals are given at V
CC
= 5V, T
A
= 25°C.
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Differential Output Voltage
vs Output Current
80
70
OUTPUT CURRENT (mA)
T
A
= 25°C
100
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
60
50
40
30
20
10
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
1324 G01
U W
Driver Output Low Voltage
vs Output Current
120
T
A
= 25°C
–90
–75
–60
–45
–30
–15
–105
Driver Output High Voltage
vs Output Current
T
A
= 25°C
80
60
40
20
0
0
0.5
1.0
1.5
2.0
OUTPUT VOLTAGE (V)
2.5
3.0
1324 G02
0
1.0
1.5
2.0 2.5 3.0 3.5 4.0 4.5
DRIVER OUTPUT HIGH VOLTAGE (V)
5.0
1324 G03
3
LTC1324
TYPICAL PERFORMANCE CHARACTERISTICS
Receiver Output Low Voltage
vs Output Current
30
T
A
= 25°C
25
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
20
15
10
5
0
0
0.4
0.8
1.2
1.6
OUTPUT VOLTAGE (V)
Receiver Short-Circuit Current
vs Temperature
19
18
900
875
SUPPLY CURRENT (µA)
OUTPUT CURRENT (mA)
17
16
15
14
13
12
11
10
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G07
800
775
750
725
700
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G08
TIME (ns)
Receiver Output Low Voltage
vs Temperature
0.8
I = 8mA
0.7
OUTPUT VOLTAGE (V)
0.5
0.4
0.3
0.2
0.1
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G10
OUTPUT VOLTAGE (V)
0.6
4
U W
1324 G04
Receiver Output High Voltage
vs Output Current
–16
–14
–12
–10
–8
–6
–4
–2
2.0
110
Driver Short-Circuit Current
vs Temperature
100
90
80
70
60
50
40
–55 –35 –15
T
A
= 25°C
0
2.0
2.5
3.0
3.5
4.0
OUTPUT VOLTAGE (V)
4.5
5.0
1324 G05
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G06
Supply Current (Driver and
Receiver Enabled) vs Temperature
4.2
4.0
3.8
3.6
3.4
3.2
Driver Skew vs Temperature
850
825
3.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G09
Receiver Output High Voltage
vs Temperature
4.00
I = 8mA
3.75
3.50
3.25
3.00
2.75
2.50
2.25
2.00
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G11
LTC1324
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Differential Output Voltage
vs Temperature
3.1
3.0
DIFFERENTIAL VOLTAGE (V)
2.9
2.8
2.7
2.6
2.5
2.4
2.3
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G12
TIME (ns)
PIN FUNCTIONS
NC (Pins 1, 13):
No Internal Connection.
SR (Pin 2):
Slew Rate Control (TTL Compatible). A high
level on this pin forces the RS485 driver into the low slew
rate mode. A low level forces the driver into the high slew
rate or normal mode. Connected to an internal pull-down.
TXD (Pin 3):
RS485 Driver Input (TTL Compatible).
TXDEN (Pin 4):
Driver Output Enable (TTL Compatible). A
high level on this pin and a low level on TXDEN (Pin 15)
forces the RS485 driver into three-state. A low level
enables the driver.
SHDN (Pin 5):
Shutdown Input (TTL Compatible). When
this pin is high, the chip is shut down; the driver and
receiver outputs three-state; and the supply current drops
to 1µA. A low level on this pin allows normal operation.
RXEN (Pin 6):
Receiver Enable (TTL Compatible). A high
level on this pin and a low level on RXEN (Pin 14) disables
the receiver and three-states the logic outputs. A low level
allows normal operation.
RXDO (Pin 7):
RS485 Receiver Output.
GND (Pin 8):
Ground.
RXD
+
(Pin 9):
RS485 Receiver Noninverting Input. When
this pin is
≥
200mV above RXD
–
, RXDO will be high. When
this pin is
≥
200mV below RXD
–
, RXDO will be low.
RXD
–
(Pin 10):
RS485 Receiver Inverting Input.
TXD
+
(Pin 11):
RS485 Driver Noninverting Output.
TXD
–
(Pin 12):
RS485 Driver Inverting Output.
RXEN (Pin 14):
Receiver Enable (TTL Compatible). A low
level on this pin and a high level on RXEN (Pin 6) disables
the receiver and three-states the logic outputs. A high level
allows normal operation. Connected to an internal pull-
down.
TXDEN (Pin 15):
Driver Output Enable (TTL Compatible).
A low level on this pin and a high level on TXDEN (Pin 4)
forces the RS485 driver into three-state. A high level
enables the driver. Connected to an internal pull-down.
V
CC
(Pin 16):
The Positive Supply Input. 4.75V
≤
V
CC
≤
5.25V. Requires a 1µF bypass capacitor to ground.
U W
Receiver
t
PLH
– t
PHL
vs Temperature
8
7
6
5
4
3
2
1
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1324 G13
R
L
= 100Ω
U
U
U
5
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