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PDF LTC1323CSW Data sheet ( Hoja de datos )
| Número de pieza | LTC1323CSW | |
| Descripción | Single 5V AppleTalk Transceiver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Single Chip Provides Complete
LocalTalk®/AppleTalk Port
s Operates From a Single 5V Supply
s ESD Protection to ±10kV on Receiver Inputs
and Driver Outputs
s Low Power: ICC = 2.4mA Typ
s Shutdown Pin Reduces ICC to 0.5µA Typ
s Receiver Keep-Alive Function: ICC = 65µA Typ
s Differential Driver Drives Either Differential
AppleTalk or Single-Ended EIA562 Loads
s Drivers Maintain High Impedance in Three-State or
with Power Off
s Thermal Shutdown Protection
s Drivers are Short-Circuit Protected
APPLICATI S
s LocalTalk Peripherals
s Notebook/Palmtop Computers
s Battery-Powered Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.
LTC1323
Single 5V
AppleTalk® Transceiver
DESCRIPTIO
The LTC®1323 is a multi-protocol line transceiver designed
to operate on AppleTalk or EIA562-compatible single-
ended networks while operating from a single 5V supply.
There are two versions of the LTC1323 available: a 16-pin
version designed to connect to an AppleTalk network,
and a 24-pin version which also includes the additional
single-ended drivers and receivers necessary to create
an Apple-compatible serial port. An on-board charge
pump generates a – 5V supply which can be used to
power external devices. Additionally, the 24-pin LTC1323
features a micropower keep-alive mode during which
one of the single-ended receivers is kept active to monitor
external wake-up signals. The LTC1323 draws only 2.4mA
quiescent current when active, 65µA in receiver keep-
alive mode, and 0.5µA in shutdown, making it ideal for
use in battery-powered systems.
The differential driver can drive either differential AppleTalk
loads or conventional single-ended loads. The driver
outputs three-state when disabled, during shutdown, in
receiver keep-alive mode, 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.
TYPICAL APPLICATI
0.33µF
1
2
CPEN 3
TXD 4
TXI 5
TXDEN 6
SHDN 7
RXEN 8
RXO 9
RXO 10
RXDO 11
12
LTC1323
CHARGE PUMP
DX
DX
RX
RX
RX
5V
24
1µF
+
23
22 0.33µF
1µF
21 +
20 TXD–
19 TXD+
18 TXO
17 RXI
16 RXI
15 RXD–
14 RXD+
13
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
5Ω TO 10Ω
EMI FILTER =
5Ω TO 10Ω
100pF
EMI FILTER
876
543
21
LTC1323 • TA01
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
Charge Pump Output Voltage
vs Load Current
–2.0
TA = 25°C
–2.5 VS = 5V
RL(DIFF) = 100Ω
–3.0 RL(SE) = 3k TO GND
VTXI = 5V
–3.5
– 4.0
– 4.5
– 5.0
–5.5
– 6.0
0
5 10 15 20 25
LOAD CURRENT (mA)
30
LTC1323 • TPC01
Supply Current vs Temperature
3.50
VS = 5V
3.25 NO LOAD
3.00
2.75
2.50
2.25
2.00
1.75
1.50
–50 –25
0 25 50 75 100 125
TEMPERATURE (˚C)
LTC1323 • TPC04
Differential Driver Swing
vs Load Resistance
5
4
3
2
1
0
–1
–2
–3
–4 TA = 25°C
VS = 5V
–5
50 100 200 300 500 1k 2k 3k 5k 10k
LOAD RESISTANCE (Ω)
LTC1323 • TPC02
Differential Driver Swing
vs Temperature
5.0
4.5
VS = 5V
RL = 100Ω
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1323 • TPC05
LTC1323
Single-Ended Driver Swing
vs Load Resistance
5
4 TA = 25°C
3 VS = 5V
2
1
0
–1
–2
–3
–4
–5
50 100 200 300 500 1k 2k 3k 5k 10k
LOAD RESISTANCE (Ω)
LTC1323 • TPC03
Single-Ended Driver Swing
vs Temperature
5
4 VS = 5V
3 RL = 3k TO GND
2
1
0
–1
–2
–3
–4
–5
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1323 • TPC06
5
5 Page 
UU W U
APPLICATIO S I FOR ATIO
Driving an External Load from VEE
An external load may be connected between ground and
the VEE pin as shown in Figure 15. The LTC1323 VEE pin
will sink up to a maximum of 10mA while maintaining the
pin voltage between – 4.5V and – 5.5V. If an external load
is connected, the VEE bypass capacitor should be in-
creased to 4.7µF. Both LTC1323 and the external chip
should have separate VCC bypass capacitors but can
share the VEE capacitor.
EMI Filter
Most LocalTalk applications use an electromagnetic inter-
ference (EMI) filter consisting of a resistor-capacitor T
network between each driver and receiver and the connec-
tor. Unfortunately, the resistors significantly attenuate the
drivers output signals before they reach the cable. Because
+
1µF
VCC = 5V
24
12
LTC1323
13
21
+ 4.7µF
VCC
EXTERNAL
CHIP
GND
VEE
–5.5V ≤ VEE ≤ –4.5V
IVEE ≤ 10mA
IVEE
Figure 15
C1
LTC1323 • F15
LTC1323
the LTC1323 uses a single supply differential driver, the
resistor values should be reduced to 5Ω to 10Ω to guaran-
tee adequate voltage swing on the cable (Figure 16a). In
most applications, removing the resistors completely does
not cause an increase in EMI as long as a shielded connec-
tor and cable are used (Figure 16b). With the resistors
removed the only DC load is the primary resistance of the
LocalTalk transformer. This will increase the DC standby
current when the driver outputs are active, but does not
adversely affect the drivers because they can handle a
direct indefinite short circuits without damage. Trans-
former primary resistance should be above 15Ω to keep the
LTC1323 operating normally and prevent it from entering
thermal shutdown. For maximum swing and EMI immu-
nity, a ferrite bead and capacitor T network can be used
(Figure 16c).
5Ω TO 10Ω
5Ω TO 10Ω
100pF
FERRITE BEAD FERRITE BEAD
100pF
100pF
(a) (b)
(c)
LTC1323 • F16
Figure 16. EMI Filters
TYPICAL APPLICATIONS N
Typical LocalTalk Connection
0.33µF
5V
+
1µF
16
1 15
2 CHARGE PUMP 14
13
0.33µF
DATA IN
TX ENABLE
SHDN
RX ENABLE
DATA OUT
3
4
5
6
7
LTC1323CS
TX
RX
8
12
11
10
9
100pF
100pF
100pF
100pF
1µF
LocalTalk
TRANSFORMER
120Ω
LTC1323 • TA02
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1323CSW.PDF ] | |
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