1
LTC1323
Single 5V
AppleTalk
®
Transceiver
DX
CHARGE PUMP
DX
RX
RX
RX
0.33µF
CPEN
TXD
TXI
TXDEN
SHDN
RXEN
RXO
RXO
RXDO
3
2
1
4
5
6
7
8
9
10
11
12
TXD
–
TXD
+
TXO
RXI
RXI
RXD
+
RXD
–
24
21
23
22
20
19
18
17
5Ω TO 10Ω
=5Ω TO 10Ω
16
14
15
13
LTC1323 • TA01
0.33µF
100pF
1µF
1µF
5V
LTC1323
876
5 4
2 1
3
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
EMI FILTER
+
+
S
FEATURE
D
U
ESCRIPTIO
■
Single Chip Provides Complete
LocalTalk
®
/AppleTalk Port
■
Operates From a Single 5V Supply
■
ESD Protection to ±10kV on Receiver Inputs
and Driver Outputs
■
Low Power: I
CC
= 2.4mA Typ
■
Shutdown Pin Reduces I
CC
to 0.5µA Typ
■
Receiver Keep-Alive Function: I
CC
= 65µA Typ
■
Differential Driver Drives Either Differential
AppleTalk or Single-Ended EIA562 Loads
■
Drivers Maintain High Impedance in Three-State or
with Power Off
■
Thermal Shutdown Protection
■
Drivers are Short-Circuit Protected
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.
U
S
A
O
PPLICATI
■
LocalTalk Peripherals
■
Notebook/Palmtop Computers
■
Battery-Powered Systems
U
A
O
PPLICATITYPICAL
AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.
, LTC and LT are registered trademarks of Linear Technology Corporation.
2
LTC1323
A
U
G
W
A
W
U
W
ARBSOLUTEXI T
I
S
Supply Voltage (V
CC
) ................................................ 7V
Input Voltage
Logic Inputs .............................. –0.3V to V
CC
+ 0.3V
Receiver Inputs ................................................ ±15V
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
WU
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
LTC1323CSLTC1323CG
ORDER PART
NUMBER
T
JMAX
= 150°C, θ
JA
= 96°C/W
ORDER PART
NUMBER
LTC1323CSW
Consult factory for Industrial and Military grade parts.
T
JMAX
= 125°C, θ
JA
= 85°C/W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
C1
+
C2
–
CPEN
TXD
TXI
TXDEN
SHDN
RXEN
RXO
RXO
RXDO
NC
NC
GND
V
CC
C2
+
C2
–
NC
NC
V
EE
TXD
–
TXD
+
TXO
RXI
RXI
RXD
–
RXD
+
PGND
G PACKAGE
28-LEAD PLASTIC SSOP
TOP VIEW
T
JMAX
= 125°C, θ
JA
= 85°C/W
1
2
3
4
5
6
7
8
TOP VIEW
S PACKAGE
16-LEAD PLASTIC SO
16
15
14
13
12
11
10
9
C1
+
C1
–
TXD
TXDEN
SHDN
RXEN
RXDO
GND
V
CC
C2
+
C2
–
V
EE
TXD
–
TXD
+
RXD
–
RXD
+
1
2
3
4
5
6
7
8
9
10
11
12
TOP VIEW
SW PACKAGE
24-LEAD PLASTIC SO WIDE
24
23
22
21
20
19
18
17
16
15
14
13
C1
+
C1
–
CPEN
TXD
TXI
TXDEN
SHDN
RXEN
RXO
RXO
RXDO
GND
V
CC
C2
+
C2
–
V
EE
TXD
–
TXD
+
TXO
RXI
RXI
RXD
–
RXD
+
PGND
3
LTC1323
ELECTRICAL CHARACTERISTICS VCC = 5V ±10%, TA = 0°C to 70°C (Notes 2, 3)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Supplies
I
CC
Normal Operation Supply Current No Load, SHDN = 0V, CPEN = 0V, TXDEN = 0V, ●2.4 4 mA
RXEN = 0V
Receiver Keep-Alive Supply Current No Load, SHDN = 0V, CPEN = V
CC
, TXDEN = 0V, ●65 100 µA
RXEN = 0V
Shutdown Supply Current No Load, SHDN = V
CC
, CPEN = X, TXDEN = X, ●0.5 10 µA
RXEN = 0V
V
EE
Negative Supply Output Voltage I
LOAD
≤ 10mA (Note 4), ●–5.5 – 5 –4.5 V
V
CC
= 5V, R
L
= 100Ω (Figure 1),
TXI = V
CC
, R
TXO
= 3k (Figure 5)
f
OSC
Charge Pump Oscillator Frequency 200 kHz
Differential Driver
V
OD
Differential Output Voltage No Load ●±8V
R
L
= 100Ω (Figure 1) ●±2
∆V
OD
Change in Magnitude of Differential R
L
= 100Ω (Figure 1) 0.2 V
Output Voltage
Differential Driver
V
OC
Differential Common-Mode R
L
= 100Ω3V
Output Voltage
V
OS
Single-Ended Output Voltage No Load ●±4.0 V
R
L
= 3k to GND ●±3.7 V
V
CMR
Common-Mode Range SHDN = V
CC
or CPEN = V
CC
or Power Off ●±10 V
I
SS
Short-Circuit Current –5V ≤ V
O
≤ 5V ●35 120 500 mA
I
OZ
Three-State Output Current SHDN = V
CC
or CPEN = V
CC
or Power Off, ●±2±200 µA
–10V ≤ V
O
≤ 10V
Single-Ended Driver (Note 5)
V
OS
Single-Ended Output Voltage No Load ●±4.5 V
R
L
= 3k to GND ●±3.7 V
V
CMR
Common-Mode Range SHDN = V
CC
or CPEN = V
CC
or TXDEN = V
CC
●±10 V
or Power Off
I
SS
Short-Circuit Current –5V ≤ V
O
≤ 5V ●35 220 500 mA
I
OZ
Three-State Output Current SHDN = V
CC
or CPEN = V
CC
or TXDEN = V
CC
●±2±200 µA
or Power Off, –10V ≤ V
O
≤ 10V
Receivers
R
IN
Input Resistance –7V ≤ V
IN
≤ 7V ●12 kΩ
Differential Receiver Threshold Voltage –7V ≤ V
CM
≤ 7V ●–200 200 mV
Differential Receiver Input Hysteresis –7V ≤ V
CM
≤ 7V ●70 mV
Single-Ended Input, Low Voltage (Note 5) ●0.8 V
Single-Ended Input, High Voltage (Note 5) ●2V
V
OH
Output High Voltage I
O
= –4mA ●3.5 V
V
OL
Output Low Voltage I
O
= 4mA ●0.4 V
I
SS
Output Short-Circuit Current –5V ≤ V
O
≤ 5V ●785mA
I
OZ
Output Three-State Current –5V ≤ V
O
≤ 5V, RXEN = V
CC
●±2±100 µA
4
LTC1323
ELECTRICAL CHARACTERISTICS VCC = 5V ±10%, TA = 0°C to 70°C (Notes 2 and 3)
The ● 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; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3: All typicals are given at V
CC
= 5V, T
A
= 25°C.
Note 4: I
LOAD
is an external current being sunk into the V
EE
pin.
Note 5: These specifications apply to the 24-pin SO Wide package only.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Logic Inputs
V
IH
Input High Voltage All Logic Input Pins ●2.0 V
V
IL
Input Low Voltage All Logic Input Pins ●0.8 V
I
C
Input Current All Logic Input Pins ●±1.0 ±20 µA
Switching Characteristics
t
PLH
, t
PHL
Differential Driver Propagation Delay R
L
= 100Ω, C
L
= 100pF (Figures 2, 7) ●40 120 ns
Differential Driver Propagation Delay R
L
= 3k, C
L
= 100pF (Figures 3, 9) ●120 180 ns
with Single-Ended Load
Single-Ended Driver Propagation Delay R
L
= 3k, C
L
= 100pF, (Figures 5, 10) (Note 5) ●40 120 ns
Differential Receiver Propagation Delay C
L
= 15pF (Figures 2, 11) ●70 160 ns
Single-Ended Receiver C
L
= 15pF (Figures 6, 12) (Note 5) ●70 160 ns
Propagation Delay
Inverting Receiver Propagation Delay C
L
= 15pF (Figures 6, 12) (Note 5) ●150 600 ns
in Keep-Alive Mode,
SHDN = 0V, CPEN = V
CC
t
SKEW
Differential Driver Output to Output R
L
= 100Ω, C
L
= 100pF (Figures 2, 7) ●10 50 ns
t
r
, t
f
Differential Driver Rise/Fall Time R
L
= 100Ω, C
L
= 100pF (Figures 2, 7) ●50 150 ns
Differential Driver Rise/Fall Time R
L
= 3k, C
L
= 100pF (Figures 3, 9) ●50 150 ns
with Single-Ended Load
Single-Ended Driver Rise/Fall Time R
L
= 3k, C
L
= 100pF (Figures 5, 10) (Note 5) ●15 80 ns
t
HDIS
, t
LDIS
Differential Driver Output Active C
L
= 15pF (Figures 4, 8) ●180 250 ns
to Disable
Any Receiver Output Active to Disable C
L
= 15pF (Figures 4, 13) ●30 100 ns
t
ENH
, t
ENL
Differential Driver C
L
= 15pF (Figures 4, 8) ●180 250 ns
Enable to Output Active
Any Receiver, Enable to Output Active C
L
= 15pF (Figures 4, 13) ●30 100 ns
V
EER
Supply Rise Time from Shutdown C1 = C2 = 0.33µF, C
VEE
= 1µF●0.2 ms
or Receiver Keep-Alive
5
LTC1323
TYPICAL PERFORMANCE CHARACTERISTICS
UW
LOAD RESISTANCE (Ω)
50
–5
SINGLE-ENDED DRIVER OUTPUT (V)
–4
–2
–1
0
5
2
200 500 1k 10k
LTC1323 • TPC03
–3
3
4
1
100 300 2k 3k 5k
T
A
= 25°C
V
S
= 5V
Single-Ended Driver Swing
vs Load Resistance
LOAD RESISTANCE (Ω)
50
–5
DIFFERENTIAL DRIVER OUTPUT (V)
–4
–2
–1
0
5
2
200 500 1k 10k
LTC1323 • TPC02
–3
3
4
1
100 300 2k 3k 5k
T
A
= 25°C
V
S
= 5V
Differential Driver Swing
vs Load Resistance
TEMPERATURE (°C)
–50
0
DIFFERENTIAL DRIVER OUTPUT (V)
0.5
1.5
2.0
2.5
5.0
3.5
050 75
LTC1323 • TPC05
1.0
4.0
4.5
3.0
–25 25 100 125
V
S
= 5V
R
L
= 100Ω
TEMPERATURE (˚C)
–50
SUPPLY CURRENT (mA)
3.25
25
LTC1323 • TPC04
2.50
2.00
–25 0 50
1.75
1.50
3.50
3.00
2.75
2.25
75 100 125
V
S
= 5V
NO LOAD
Differential Driver Swing
vs TemperatureSupply Current vs Temperature
LOAD CURRENT (mA)
0
CHARGE PUMP OUTPUT VOLTAGE (V)
–4.5
–4.0
–3.5
15 25
LTC1323 • TPC01
–5.0
–5.5
–6.0 510 20
–3.0
–2.5
–2.0
30
T
A
= 25°C
V
S
= 5V
R
L(DIFF)
= 100Ω
R
L(SE)
= 3k TO GND
V
TXI
= 5V
Charge Pump Output Voltage
vs Load Current
TEMPERATURE (°C)
–50
–5
SINGLE-ENDED DRIVER OUTPUT (V)
–4
–2
–1
0
5
2
050 75
LTC1323 • TPC06
–3
3
4
1
–25 25 100 125
V
S
= 5V
R
L
= 3k TO GND
Single-Ended Driver Swing
vs Temperature
6
LTC1323
PI FU CTIO S
U
UU
LTC1323CSW
C1
+
: C1 Positive Input. Connect a 0.33µF capacitor be-
tween C1
+
and C1
–
.
C1
–
: C1 Negative Input. Connect a 0.33µF capacitor be-
tween C1
+
and C1
–
.
CPEN: TTL Level Charge Pump Enable Input. With CPEN
held low, the charge pump is enabled and the chip oper-
ates normally. When CPEN is pulled high, the charge
pump is disabled as well as both drivers, the noninverting
single-ended receiver, and the differential receiver. The
inverting single-ended receiver (RXI) is kept
alive to
monitor the control line and ICC drops to 65µA. To turn
off the receiver and drop ICC to 0.5µA, pull the SHDN pin
high.
TXD: Differential Driver Input (TTL compatible).
TXI: Single-Ended Driver Input (TTL compatible).
TXDEN: Differential Driver Output Enable (TTL compat-
ible). A high level on this pin forces the differential driver
into three-state; a low level enables the driver. This input
does not affect the single-ended driver.
SHDN: Shutdown Input (TTL compatible). When this pin
is high, the chip is shut down. All driver and receiver
outputs are three-state, the charge pump turns off, and the
supply current drops to 0.5µA. A low level on this pin
allows normal operation.
RXEN:
Receiver Enable (TTL compatible). A high level
on this pin disables the receivers and three-states the
logic outputs; a low level allows normal operation.
RXO: Inverting Single-Ended Receiver Output. Remains
active in the receiver keep-alive mode.
RXO: Noninverting Single-Ended Receiver Output.
RXDO: Differential Receiver Output.
GND:
Signal Ground. Connect to PGND with 24-pin
package.
PGND: Power ground is connected internally to the charge
pump and differential driver. Connect to the GND pin.
RXD
+
: Differential 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
–
: Differential Receiver Inverting Input.
RXI: Noninverting Receiver Input. This input controls the
RXO output.
RXI: Inverting Receiver Input. This input controls the RXO
output. In receiver keep-alive mode (CPEN high, SHDN
low), this receiver can be used to monitor a wake-up
control signal.
DX
CHARGE PUMP
DX
RX
RX
RX
C1
+
C1
–
CPEN
TXD
TXI
TXDEN
SHDN
RXEN
RXO
RX0
RXDO
GND
V
CC
V
EE
C2
+
C2
–
TXD
–
TXD
+
TXO
RXI
RXI
RXD
–
RXD
+
PGND
24
21
23
22
20
19
18
17
16
15
14
13
1
4
2
3
5
6
7
8
9
10
11
12
LTC1323CG
DX
CHARGE PUMP
DX
RX
RX
RX
C1+
C1–
CPEN
TXD
TXI
TXDEN
SHDN
RXEN
RXO
RX0
RXDO
NC
GND
NC
VCC
VEE
C2+
C2–
TXD–
NC
NC
TXD+
TXO
RXI
RXI
RXD–
RXD+
PGND
28
25
27
26
24
23
22
21
20
19
18
17
15
16
1
4
2
3
5
6
7
8
9
10
11
12
13
14
LTC1323CS
DX
CHARGE PUMP
RX
C1
+
C1
–
TXD
TXDEN
SHDN
RXEN
RXDO
GND
V
CC
V
EE
C2
+
C2
–
TXD
–
TXD
+
RXD
–
RXD
+
16
13
15
14
12
11
10
9
1
4
2
3
5
6
7
8
7
LTC1323
TXO: Single-Ended Driver Output.
TXD
+
: Differential Driver Noninverting Output.
TXD
–
: Differential Driver Inverting Output.
V
EE
: Negative Supply Charge Pump Output. Requires a
1µF bypass capacitor to ground. If an external load is
connected to the V
EE
pin, the bypass capacitor value
should be increased to 4.7µF.
PI FU CTIO S
U
UU
C2
–
: C2 Negative Input. Connect a 0.33µF capacitor
between C2
+
and C2
–
.
C2
+
: C2 Positive Input. Connect a 0.33µF capacitor
between C2
+
and C2
–
.
V
CC
: Positive Supply Input. 4.5V ≤ V
CC
≤ 5.5V. Requires a
1µF bypass capacitor to ground.
TEST CIRCUITS
R
R
V
OD
TXD
+
TXD
–
LTC1323 • F01
V
OC
R
L
C
L
LTC1323 • F02
RXD
+
TXD
–
RXD
+
RXD
–
RXDO
C
L
15pF
TXI
Figure 1 Figure 2 Figure 3
LTC1323 • F03
TXD
–
TXD
+
TXI
C
L
R
L
C
L
R
L
OUTPUT
C
L
500Ω
S2
LTC1323 • F04
V
CC
S1
LTC1323 • F06
RXORXI
C
L
RXORXI
C
L
R
L
LTC1323 • F05
TXOTXI
C
L
Figure 4 Figure 5 Figure 6
SWITCHI G WAVEFOR S
UW
1.5V
3V
0V
TXD f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns 1.5V
–V
O
V
O
t
SKEW
1/2 V
O
LTC1323 • F07
t
PLH
t
r
90%
50%
10%
t
PHL
t
f
90% 50%
10%
V
O
t
SKEW
V
DIFF
= V(TXD
+
) – V(TXD
–
)
TXD
–
TXD
+
Figure 7. Differential Driver
8
LTC1323
SWITCHI G WAVEFOR S
UW
1.5V
3V
0V
TXDEN f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns 1.5V
TXD
+
, TXD
–
TXD
–
, TXD
+
V
OL
5V
t
ZL
t
LZ
0.5V
OUTPUT NORMALLY LOW
0V
LTC1323 • F08
2.3V
2.3V
t
ZH
V
OH
OUTPUT NORMALLY HIGH t
HZ
0.5V
Figure 8. Differential Driver Enable and Disable
Figure 11. Differential Receiver
V
OD2
(RXD
+
) – (RXD
–
)
RXDO
V
OL
V
OH
LTC1323 • F11
t
PLH
t
PHL
–V
OD2
1.5V
1.5V
0V 0V
f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns
1.5V
3V
0V
TXD
TXD
–
TXD
+
f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns 1.5V
V
OL
V
OH
V
OL
V
OH
LTC1323 • F09
t
PHL
t
r
90%
0V
0V
10%
t
PLH
t
f
90%
0V
0V
10%
Figure 9. Differential Driver With Single-Ended Load
3V
TXI
TXO
V
OL
V
OH
LTC1323 • F10
t
PHL
t
PLH
0V
0V
0V
90% 90%
10% 10%
1.5V 1.5V
t
r
t
r
f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns
Figure 10. Single-Ended Driver
9
LTC1323
SWITCHI G WAVEFOR S
UW
Figure 12. Single-Ended Receiver
1.5V
RXI, RXI
RXI
RXI
1.5V
V
OL
V
OH
V
IL
V
IH
V
V
IH
LTC1323 • F12
t
PHL
0.8V
1.5V
t
PLH
2.4V
1.5V
f = 1MHz: t
r
≤ 10ns: t
f
≤ 10ns
Figure 13. Receiver Enable and Disable
1.5V
3V
0V
RXEN f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V
RXO, RXO, RXDO
VOL
5V
tZL tLZ
0.5V
OUTPUT NORMALLY LOW
0V
LTC1323 • F13
2.3V
2.3V
tZH
VOH OUTPUT NORMALLY HIGH tHZ
0.5V
RXO, RXO, RXDO
APPLICATIO S I FOR ATIO
UU W U
Functional Description
The “serial port” on the back of an Apple-compatible
computer or peripheral is a fairly versatile “multi-protocol”
connector. It must be able to connect to a wide bandwidth
LAN (an AppleTalk/LocalTalk network), which requires a
high speed differential transceiver to meet the AppleTalk
specification, and it must also be able to connect directly to
a printer or modem through a short RS232 style link. The
LTC1323 is designed to provide all the functions necessary
to implement such a port on a single chip. Two versions of
the LTC1323 are available: a 16-pin SO version which
provides the minimum solution for interfacing to an
AppleTalk network in a smaller package, and a larger 24-pin
SO Wide version which additionally includes all the hand-
shaking lines required to implement a complete AppleTalk/
modem/printer serial port. All LTC1323s run from a single
5V power supply while providing true single-ended com-
patibility, and include a 0.5µA low power shutdown mode
to improve lifetime in battery-powered devices. The 24-
pin SO Wide version also includes a receiver keep-alive
mode for monitoring external signals while drawing 65µA
typically.
The LTC1323 includes an RS422-compatible differential
driver/receiver pair for data transmission, with the driver
specified to drive 2V into the 100Ω primary of a typical
LocalTalk interface transformer/RFI interference network.
Either output of the differential RS422 driver can also act as
an single-ended driver, allowing the LTC1323 to commu-
nicate over a standard serial connection. The 24-pin SO
Wide LTC1323 also includes an extra single ended only
driver and two extra RS232-compatible single-ended re-
ceivers for handshaking lines. All versions include an on-
board charge pump to provide a regulated –5V supply
required for the single-ended drivers. The charge pump
can also provide up to 10mA of external load current to
power other circuitry.
10
LTC1323
APPLICATIO S I FOR ATIO
UU W U
Driving Differential AppleTalk or Single-Ended Loads
The differential driver is able to drive either an AppleTalk
load or a single-ended load such as a printer or modem.
With a differential AppleTalk load, TXD
+
and TXD
–
will
typically swing between 1.2V and 3.5V (Figure 14a). With
a single-ended 3k load such as a printer, either TXD
+
or
TXD
–
will meet the single-ended voltage swing require-
ment of ±3.7V (Figure 14b). An automatic switching circuit
prevents the differential driver from overloading the charge
pump if the outputs are shorted to ground while driving
single-ended signals. This allows the second single-ended
driver to continue to operate normally when the first is
shorted, and allows external circuitry attached to the charge
pump output to continue to operate even if there are faults
at the driver outputs.
Power Shutdown
The power shutdown feature of the LTC1323 is designed
for battery-powered systems. When SHDN is forced
high the part enters shutdown mode. In shutdown the
supply current typically drops from 2.4mA to 0.5µA , the
charge pump turns off, and the driver and receiver
outputs are three-stated.
Receiver Keep-Alive Mode (24-Pin SO Wide Only)
The 24-pin SO Wide version of the LTC1323 also features
a power saving receiver keep-alive mode. When CPEN is
pulled high the charge pump is turned off and the outputs
of both drivers, the noninverting single-ended receiver and
the differential receiver are forced into three-state. The
inverting single-ended receiver (RXI) is kept alive with I
CC
dropping to 65µA and the receiver delay time increasing to
a maximum of 400ns. The receiver can then be used to
monitor a wake-up control signal.
Charge Pump Capacitors and Supply Bypassing
The LTC1323 requires two external 0.33µF capacitors for
the charge pump to operate: one from C1
+
to C1
–
and one
from C2
+
to C2
–
. These capacitors should be low ESR
types and should be mounted as close as possible to the
LTC1323. Monolithic ceramic capacitors work well in this
application. Do not use capacitors greater than 2µF at the
charge pump pins or internal peak currents can rise to
destructive levels. The LTC1323 also requires that both V
CC
and V
EE
be well bypassed to ensure proper charge pump
operation and prevent data errors. A 1µF capacitor from
V
CC
to ground is adequate. A 1µF capacitor is required from
V
EE
to ground and should be increased to 4.7µF if an
external load is connected to the V
EE
pin. Ceramic or
tantalum capacitors are adequate for power supply by-
passing; aluminum electrolytic capacitors should only be
used if their ESR is low enough for proper charge pump
operation. Inadequate bypass or charge pump capacitors
will cause the charge pump output to go out of regulation
prematurely, degrading the output swing at the SINGLE-
ENDED driver outputs.
EXTERNAL
CHIP
V
CC
V
EE
I
VEE
GND
12
24
21
1µF
4.7µF
LTC1323 • F15
–5.5V ≤ V
EE
≤ –4.5V
I
VEE
≤ 10mA
13
LTC1323
V
CC
= 5V
C1
+
+
Thermal Shutdown Protection
The LTC1323 includes a thermal shutdown circuit which
protects against prolonged shorts at the driver outputs. If
a driver output is shorted to another output or to the power
supply, the current will be initially limited to a maximum of
500mA. When the die temperature rises above 150°C, the
thermal shutdown circuit disables the driver outputs.
When the die cools to about 130°C, the outputs are re-
enabled. If the short still exists, the part will heat again and
the cycle will repeat. This oscillation occurs at about 10Hz
and prevents the part from being damaged by excessive
power dissipation. When the short is removed, the part will
return to normal operation.
Figure 14
11
LTC1323
Driving an External Load from V
EE
An external load may be connected between ground and
the V
EE
pin as shown in Figure 15. The LTC1323 V
EE
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 V
EE
bypass capacitor should be in-
creased to 4.7µF. Both LTC1323 and the external chip
should have separate V
CC
bypass capacitors but can
share the V
EE
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
APPLICATIO S I FOR ATIO
UU W U
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).
Figure 16. EMI Filters
EXTERNAL
CHIP
V
CC
V
EE
I
VEE
GND
12
24
21
1µF
4.7µF
LTC1323 • F15
–5.5V ≤ V
EE
≤ –4.5V
I
VEE
≤ 10mA
13
LTC1323
V
CC
= 5V
C1
+
+
Figure 15
TX
15
16
0.33µF
14
13
12
11
10
9
8
1
2
5
6
7
3
4
CHARGE PUMP
LTC1323CS
5V
LocalTalk
TRANSFORMER
RX
100pF
100pF 120Ω
100pF
100pF
LTC1323 • TA02
0.33µF
SHDN
DATA IN
TX ENABLE
RX ENABLE
DATA OUT
1µF
1µF
+
+
Typical LocalTalk Connection
TYPICAL APPLICATIONS N
U
5Ω TO 10Ω5Ω TO 10Ω
(a) (b) (c)
100pF
FERRITE BEAD FERRITE BEAD
100pF
LTC1323 • F16
100pF
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.
12
LTC1323
PACKAGE DESCRIPTION
U
Dimensions in inches (millimeters) unless otherwise noted.
S24 (WIDE) 0695
NOTE 1
0.598 – 0.614*
(15.190 – 15.600)
22 21 20 19 18 17 16 15
12345678
0.394 – 0.419
(10.007 – 10.643)
910
1314
11 12
2324
0.037 – 0.045
(0.940 – 1.143)
0.004 – 0.012
(0.102 – 0.305)
0.093 – 0.104
(2.362 – 2.642)
0.050
(1.270)
TYP 0.014 – 0.019
(0.356 – 0.482)
0° – 8° TYP
NOTE 1
0.009 – 0.013
(0.229 – 0.330) 0.016 – 0.050
(0.406 – 1.270)
0.291 – 0.299**
(7.391 – 7.595)
× 45°
0.010 – 0.029
(0.254 – 0.737)
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS.
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
SW Package
24-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
G Package
28-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
G28 SSOP 0694
0.005 – 0.009
(0.13 – 0.22)
0° – 8°
0.022 – 0.037
(0.55 – 0.95)
0.205 – 0.212**
(5.20 – 5.38)
0.301 – 0.311
(7.65 – 7.90)
12345678 9 10 11 12 1413
0.397 – 0.407*
(10.07 – 10.33)
2526 22 21 20 19 18 17 16 1523242728
0.068 – 0.078
(1.73 – 1.99)
0.002 – 0.008
(0.05 – 0.21)
0.0256
(0.65)
BSC 0.010 – 0.015
(0.25 – 0.38)
DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
S Package
16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.016 – 0.050
0.406 – 1.270
0.010 – 0.020
(0.254 – 0.508)× 45°
0° – 8° TYP
0.008 – 0.010
(0.203 – 0.254)
S16 0695
12345678
0.150 – 0.157**
(3.810 – 3.988)
16 15 14 13
0.386 – 0.394*
(9.804 – 10.008)
0.228 – 0.244
(5.791 – 6.197)
12 11 10 9
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
TYP
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900
●
FAX
: (408) 434-0507
●
TELEX
: 499-3977
LINEAR TECHNOLOGY CORPORATION 1994
LT/GP 1194 10K • PRINTED IN USA
