LT1331
3V RS562 or 5V/3V RS232
Transceiver with One Receiver
Active in Shutdown
FEATURES
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
RS232 Compatible 3V Operation
3V Logic Interface
ESD Protection Over
±10kV
120kbaud Operation for R
L
= 3k, C
L
= 2500pF
250kbaud Operation for R
L
= 3k, C
L
= 1000pF
One Low Power Receiver Remains Active While
in Shutdown
60µA Supply Current in Shutdown
Low Power Driver Disable Mode
Uses Small Capacitors: 0.1µF, 0.2µF
CMOS Comparable Low Power: 60mW
Easy PC Layout: Flowthrough Architecture
Rugged Bipolar Design
Outputs Assume a High Impedance State When
Off or Powered Down
The LT
®
1331 is a 3-driver, 5-receiver RS232 transceiver
designed for 3V and mixed 3V/5V systems. Receivers
operate from 3V logic supply V
L
, while the onboard charge
pump and drivers operate from 5V or 3V supply V
CC
.
The transceiver has two shutdown modes. One mode
disables the drivers and the charge pump, the other shuts
down all circuitry except for one low power receiver which
can be used for ring detection. The V
CC
supply may be shut
down while in ring detection mode. While shut down, the
drivers and receivers assume high impedance output
states.
The LT1331 is fully compliant with all EIA-RS232 specifi-
cations when V
CC
= 5V. If V
CC
= 3V, output drive levels are
compatible with all known interface circuits. Special bipo-
lar construction techniques protect the drivers and receiv-
ers beyond the fault conditions stipulated for RS232. The
RS232 I/O pins are resilient to multiple
±10kV
ESD strikes.
An advanced driver output stage operates up to 120kbaud
while driving heavy capacitive loads.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s
s
S
Notebook Computers
Palmtop Computers
TYPICAL APPLICATI
+
0.1µF
2
×
0.1µF
V
+
1
2
3
4
DRIVER 1 OUT
RX1 IN
DRIVER 2 OUT
TO LINE
RX2 IN
RX3 IN
RX4 IN
DRIVER 3 OUT
RX5 IN (LOW-Q)
ON/OFF
3.3V V
L
5
6
7
8
9
10
11
12
13
14
LT1331
V
CC
= 3.3V
3.3V Operation
28 V
–
27
25
24
23
22
21
20
19
0.1µF
26
DRIVER 1 IN
RX1 OUT
DRIVER 2 IN
RX2 OUT
RX3 OUT
RX4 OUT
INPUT
R
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
RECEIVER
OUTPUT
C
L
= 50pF
DRIVER 3 IN
18 RX5 OUT (LOW-Q)
17
GND
16
DRIVER DISABLE
15
NC
+
+
TO LOGIC
RING DETECT IN
µCONTROLLER
OR
µPROCESSOR
SHUTDOWN
CONTROL OUT
1331 TA01
1331 TA02
+
2
×
0.1µF
U
UO
UO
1
LT1331
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
+
1
28
V
–
5V/3V V
CC
2
C1
+
3
C1
–
4
DRIVER 1 OUT 5
RX1 IN 6
DRIVER 2 OUT 7
RX2 IN 8
RX3 IN 9
RX4 IN 10
DRIVER 3 OUT 11
RX5 IN
(LOW-Q) 12
ON/OFF 13
3.3V V
L
14
G PACKAGE
28-LEAD SSOP
27 C2
–
26 C2
+
25 DRIVER 1 IN
24 RX1 OUT
23 DRIVER 2 IN
22 RX2 OUT
21 RX3 OUT
20 RX4 OUT
19 DRIVER 3 IN
RX5 OUT
18 (LOW-Q)
17 GND
16 DRIVER
DISABLE
15 NC
NW PACKAGE
28-LEAD PDIP
Supply Voltage (V
CC
) ................................................ 6V
Supply Voltage (V
L
) .................................................. 6V
V
+
........................................................................ 13.2V
V
–
...................................................................... –13.2V
Input Voltage
Driver ........................................................... V
+
to V
–
Receiver ................................................ 30V to – 30V
ON/OFF ...................................... – 0.3V to V
CC
+ 0.3V
DRIVER DISABLE ...................... – 0.3V to V
CC
+ 0.3V
Output Voltage
Driver ................................................... – 30V to 30V
Receiver ...................................... – 0.3V to V
L
+ 0.3V
Short Circuit Duration
V
+
................................................................... 30 sec
V
–
................................................................... 30 sec
Driver Output .............................................. Indefinite
Receiver Output .......................................... 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
LT1331CG
LT1331CNW
LT1331CSW
SW PACKAGE
28-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 96°C/ W (G)
T
JMAX
= 125°C,
θ
JA
= 56°C/ W (NW)
T
JMAX
= 125°C,
θ
JA
= 85°C/ W (SW)
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
Power Supply Generator
V
+
Output
V
–
Output
Supply Current (V
CC
)
Supply Current (V
L
)
Supply Current When OFF (V
CC
)
Supply Current When OFF (V
L
)
Supply Rise Time, Shutdown to Turn-On
ON/OFF Pin Thresholds
ON/OFF Pin Current
DRIVER DISABLE Pin Thresholds
DRIVER DISABLE Pin Current
Oscillator Frequency
CONDITIONS
(Note 2)
MIN
TYP
8.6
5.5
– 7.0
– 4.8
12
12
3
2
0.1
60
3
0.2
1.4
1.4
1.4
1.4
130
MAX
UNITS
V
V
V
V
mA
mA
mA
µA
mA
µA
mA
ms
V
V
µA
V
V
µA
kHz
V
CC
= 5V
V
CC
= 3.3V
V
CC
= 5V
V
CC
= 3.3V
V
CC
= 5V (Note 3)
V
CC
= 3.3V
(Note 4)
Shutdown (Note 5)
Driver Disable
Shutdown (Note 5)
Driver Disable
C1 = C2 = 0.2µF, C
+
= C
–
= 0.1µF
Input Low Level (Device Shut Down)
Input High Level (Device Enabled)
0V
≤
V
ON/OFF
≤
5V
Input Low Level (Drivers Enabled)
Input High Level (Drivers Disabled)
0V
≤
V
DRIVER DISABLE
≤
5V
q
q
q
q
q
17
17
5
50
1
100
5
0.8
80
0.8
500
q
q
q
q
q
q
2.4
–15
2.4
–10
2
U
W
U
U
W W
W
LT1331
ELECTRICAL CHARACTERISTICS
PARAMETER
Any Driver
Output Voltage Swing, Positive
Output Voltage Swing, Negative
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Data Rate (Note 8)
Slew Rate
Propagation Delay
Any Receiver
Input Voltage Thresholds
Hysteresis
Input Resistance
Receivers 1 Through 4
Output Voltage
Output Short-Circuit Current
Propagation Delay
Output Leakage Current
Receiver 5 (Low Q-Current RX)
Output Voltage
Output Short-Circuit Current
Propagation Delay
CONDITIONS
V
CC
= 5V, R
L
= 3k
V
CC
= 3.3V, R
L
= 3k
V
CC
= 5V, R
L
= 3k
V
CC
= 3.3V, R
L
= 3k
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
0.8V
≤
V
IN
≤
2V
V
OUT
= 0V
Shutdown V
OUT
=
±30V
(Note 5)
R
L
= 3k, C
L
= 2500pF
R
L
= 3k, C
L
= 1000pF
R
L
= 3k, C
L
= 51pF
R
L
= 3k, C
L
= 2500pF
Output Transition t
HL
High to Low (Note 6)
Output Transition t
LH
Low to High
Input Low Threshold (V
OUT
= High)
Input High Threshold (V
OUT
= Low)
V
IN
=
±10V
Output Low, I
OUT
= – 1.6mA
Output High, I
OUT
= 160µA (V
L
= 3.3V)
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
Output Transition t
HL
High to Low (Note 7)
Output Transition t
LH
Low to High
Shutdown (Note 5) 0
≤
V
OUT
≤
V
CC
Output Low, I
OUT
= – 500µA
Output High, I
OUT
= 160µA (V
L
= 3V)
Sinking Current, V
OUT
= V
CC
Sourcing Current, V
OUT
= 0V
Output Transition t
HL
High to Low (Note 7)
Output Transition t
LH
Low to High
q
q
q
q
q
q
q
MIN
5.0
3.7
TYP
6.5
4.0
– 6.0
– 3.3
1.4
1.4
5
17
10
MAX
UNITS
V
V
V
V
V
V
µA
mA
µA
kBaud
kBaud
V/µs
V/µs
µs
µs
V
V
V
kΩ
V
V
mA
mA
ns
ns
µA
V
V
mA
mA
µs
µs
– 5.0
– 2.7
0.8
20
100
2.0
±9
q
120
250
15
6
0.6
0.5
q
q
q
30
1.3
1.3
0.8
0.1
3
1.3
1.7
0.4
5
0.2
2.4
– 20
20
250
350
1
0.2
2.4
–4
4
1
1
2.4
1.0
7
0.4
– 10
600
600
10
0.4
–2
3
3
2.0
10
q
q
q
2.0
2
The
q
denotes specifications which apply over the full operating
temperature range (0°C
≤
T
A
≤
70°C for commercial grade).
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Testing done at V
CC
= 5V, V
L
= 3.3V, and V
ON/OFF
= 3V, unless
otherwise stated.
Note 3:
Supply current is measured as the average over several charge
pump cycles. C
+
= 1µF, C
–
= 0.1µF, C1 = C2 = 0.2µF. All outputs are open
with all driver inputs tied high.
Note 4:
V
L
supply current is measured with all receiver outputs high.
Note 5:
Supply current and leakage current measurements in shutdown
are performed with V
ON/OFF
≤
0.1V. Supply current measurements using
driver disable are performed with V
DRIVER DISABLE
≥
3V.
Note 6:
For driver delay measurements, R
L
= 3k and C
L
= 51pF. Trigger
points are set between the driver’s input logic threshold and the output
transition to the zero crossing (t
HL
= 1.4V to 0V and t
LH
= 1.4V to 0V).
Note 7:
For receiver delay measurements, C
L
= 51pF. Trigger points are
set between the receiver’s input logic threshold and the output transition
to standard TTL/CMOS logic threshold (t
HL
= 1.3V to 2.0V and t
LH
= 1.7V
to 0.8V).
Note 8:
Data rate operation guaranteed by slew rate, short-circuit current
and propagation delay tests.
3
LT1331
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Short-Circuit Current
30
V
CC
= 5V
SHORT-CIRCUIT CURRENT (mA)
DRIVER OUTPUT VOLTAGE (V)
8
OUTPUT HIGH
V
CC
= 5V
6
5
V
CC
= 3.3V
4
3
R
L
= 3k
3 DRIVERS
LOADED
50
25
75
0
TEMPERATURE (°C)
100
125
7
DRIVER OUTPUT VOLTAGE (V)
25
20
I
SC+
15
10
5
0
–55 –25
I
SC–
50
25
75
0
TEMPERATURE (°C)
Driver Leakage in Shutdown
100
16
14
LEAKAGE CURRENT (µA)
10
SLEW RATE (V/µs)
SLEW RATE (V/µs)
1
V
OUT
= 30V
V
OUT
= –30V
0.1
–55 –25
50
25
0
75
TEMPERATURE (°C)
Supply Current vs Data Rate
50
R
L
= 3k
C
L
= 2500pF
THRESHOLD VOLTAGE (V)
3.00
2.75
40
SUPPLY CURRENT (mA)
V
CC
= 5V
V
CC
= 3.3V
3 DRIVERS
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
INPUT LOW
INPUT HIGH
SHORT-CIRCUIT CURRENT (mA)
30
20
10
1 DRIVER
0
0
25
V
CC
= 3.3V
50
75
100
DATA RATE (kBAUD)
4
U W
100
1331 G01
Driver Output Voltage
–2
Driver Output Voltage
OUTPUT LOW
–3
–4
–5
–6
–7
R
L
= 3k
3 DRIVERS
LOADED
50
25
75
0
TEMPERATURE (°C)
100
125
V
CC
= 5V
V
CC
= 3.3V
125
2
–55 –25
–8
–55 –25
1331 G02
1331 G03
Slew Rate vs Load Capacitance
16
V
CC
= 5V
Slew Rate vs Load Capacitance
14
12
10
8
–SLEW
6
4
2
0
+SLEW
V
CC
= 3.3V
12
10
8
6
+SLEW
4
2
–SLEW
100
125
0
0
1
3
4
2
LOAD CAPACITANCE (nF)
5
1331 G05
0
1
3
4
2
LOAD CAPACITANCE (nF)
5
1331 G06
1331 G04
Receiver Input Thresholds
40
V
L
= 3.3V
Receiver Short-Circuit Current
V
L
= 3.3V
I
SC–
30
I
SC+
20
V
CC
= 5V
10
125
150
0.50
–55 –25
50
25
0
75
TEMPERATURE (°C)
100
125
0
–55 –25
50
0
75
25
TEMPERATURE (°C)
100
125
1131 G07
1331 G08
1331 G09
LT1331
PI FU CTIO S
V
+
(Pin 1):
Positive Supply Output. V
+
≅
2V
CC
– 1.5V. This
pin requires an external capacitor for charge storage,
chosen to minimize ripple to acceptable levels. A mini-
mum size of 0.1µF is recommended.
V
CC
(Pin 2):
Power Supply for Charge Pump and Drivers.
Proper circuit operation is insured for V
CC
= 3V to 6V.
V
CC
= 5V operation gives full RS232 compliant perfor-
mance, 3V operation results in lower driver output ampli-
tude. The V
CC
pin should be decoupled with a 0.1µF
ceramic capacitor.
C1
+
, C1
–
, C2
+
, C2
–
(Pins 3, 4, 26, 27):
These pins require
two external capacitors C
≥
0.2µF. One from C1
+
to C1
–
,
and another from C2
+
to C2
–
. To maintain charge pump
efficiency, the capacitor’s effective series resistance should
be less than 2Ω. Low ESR tantalum capacitors work well
in this application, small value ceramic capacitors may
also be used with minimal reduction in charge pump
compliance.
DRIVER OUT (Pins 5, 7, 11):
RS232 Driver Outputs.
Outputs are in a high impedance state when in shutdown,
driver disable, or V
CC
= 0V. Outputs are fully short-circuit
protected from V
–
+ 30V to V
+
– 30V. Although the
outputs are protected, short circuits on one output can
load the power supply generator and may disrupt the
signal levels of the other outputs. The driver outputs are
protected against ESD to
±10kV
for human body model
discharges. Output levels of – 3.3V to 4V are achieved
when the circuit is operated with V
CC
= 3.3V.
RX IN (Pins 6, 8, 9, 10):
Receiver Inputs with 0.4V of
Hysteresis for Noise Immunity. These pins accept RS232
level signals (±30V) into a protected 5k terminating
resistor. The receiver inputs are protected against ESD to
±10kV
for human body model discharges.
LOW-Q RX IN (Pin 12):
Low Power Receiver Input. This
receiver remains active in shutdown mode, consuming
only 60µA from supply V
L
. This receiver has the same
input and protection characteristics as receivers RX1
through RX4.
ON/OFF (Pin 13):
A TTL/CMOS Compatible Operating
Mode Control. A logic low puts the device in the shutdown
mode. All drivers and four of the receivers go to a high
impedance state, and the V
CC
supply may be turned off. A
logic high fully enables the transceiver.
V
L
(Pin 14):
Power Supply for Receivers. This pin should
be powered to the same voltage as the logic circuits
connected to the receiver outputs, either 5V or 3V. The V
L
pin should be decoupled with a 0.1µF ceramic capacitor.
DRIVER DISABLE (Pin 16):
A logic high shuts down the
charge pump, placing all drivers in a high impedance state.
All receivers remain active. Floating the pin, or driving it
to a logic low, fully enables the transceiver. A low voltage
on the ON/OFF pin supersedes the state of the driver
disable control.
GND (Pin 17):
Ground.
LOW-Q RX OUT (Pin 18):
Low Power Receiver Output.
This pin produces the same output levels as standard
receivers, with slightly decreased speed and short-circuit
current.
DRIVER IN (Pins 19, 23, 25):
RS232 Driver Inputs.
Inputs are TTL/CMOS compatible. Tie unused inputs
to V
CC
.
RX OUT (Pins 20, 21, 22, 24):
Receiver Outputs. RX1
through RX4 outputs are in a high impedance state when
in shutdown mode to allow data line sharing. Outputs,
including LOW-Q RX OUT, are fully short-circuit pro-
tected to ground, V
CC
, or V
L
. Output voltage levels are
determined by the choice of power supply V
L
.
V
–
(Pin 28):
Negative Supply Output. V
–
≅
– (2V
CC
–
2.5V). This pin requires an external charge storage
capacitor, chosen to minimize ripple on V
–
. A minimum
value of 0.1µF is recommended.
U
U
U
5
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