LT1332
Wide Supply Range
Low Power RS232 Transceiver with
12V VPP Output for Flash Memory
FEATURES
s
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
Generates Full RS232 Signal Levels from 3V Supply
12V VPP Output Available for Flash Memory
Useful with a Wide Variety of Switching Regulators
Low Supply Current: I(V
CC
) = 1mA
Wide Supply Range: 2V
≤
V
CC
≤
6V
ESD Protection Over
±10kV
Operates to 120k Baud
Outputs Assume a High Impedance State When Off
or Powered Down
One
µPower
Receiver Remains Active While in
SHUTDOWN
Flowthrough Architecture Eases PC Board Layout
40µA Supply Current in SHUTDOWN
Absolutely No Latch-Up
Available in SO and SSOP Packages
The LT1332 is a 3-driver/5-receiver RS232 transceiver,
designed to be used in conjunction with a switching
regulator. The LT1332 shares the regulator’s positive
output, while charge is capacitively pumped from the
regulator’s switch pin to the negative supply. Schottky
rectifiers built into the LT1332 simplify the charge
pump design.
The LT1332/LT1109A combination shown below gener-
ates fully compliant RS232 signal levels from as little as 2V
of input supply. The switcher can deliver greater than
100mA of output current, making the LT1332 an excellent
choice for mouse driver circuits.
Advanced driver output stages operate up to 120k baud
while driving heavy capacitive loads. New ESD structures
on chip make the LT1332 resilient to multiple
±10kV
strikes, eliminating costly transient suppressors.
A shutdown pin disables the transceiver except for one
receiver which remains active for detecting incoming
RS232 signals. When shut down, the disabled drivers and
receivers assume high impedance output states.
APPLICATI
s
s
S
Notebook and Palmtop Computers
Mouse Driver Circuits
TYPICAL APPLICATI
STANDARD FLASH MEMORY VPP GENERATOR
SWITCHER
V
IN
2 AA
BATTERIES
UP TO 6V
L1**
33µH
22µF*
V
IN
SW
LT1109A-12
SW
SENSE
ON/OFF
GND
PGND
LT1332 Powered from an LT1109A Micropower Switching Regulator
Configured for Flash Memory
12V VPP
OUTPUT
+
1µF
V
+
1
24
23
22
21
20
19
18
17
16
15
14
LT1332
13
RS232
ON/OFF
LOGIC
SIDE
V
–
10µF
C
–
2
3
4
5
RS232
SIDE
6
7
8
MBRS130T3
DRIVER
INPUT
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
ON/OFF
* AVX TAJE226K035
** SUMIDA CD54-330N (708-956-0666)
9
10
NC
11
12
0.1µF
LT1332 • TA01
3V
RS232
V
CC
+
22µF*
RECEIVER
OUTPUT
C
L
= 50pF
LT1332 • TA02
U
Output Waveforms
UO
UO
1
LT1332
ABSOLUTE
(Note 1)
AXI U
RATI GS
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
Supply Voltage (V
CC
) ................................................ 6V
V
+
........................................................................ 13.2V
V
–
...................................................................... – 13.2V
C
–
......................................................................... – 15V
Input Voltage
Driver .......................................................... V
+
to V
–
Receiver ................................................ 30V to – 30V
Output Voltage
Driver .................................................... 30V to – 30V
Receiver .................................... – 0.3V to V
CC
+ 0.3V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
NC 1
NC 2
V
+
3
C
–
4
DRIVER OUT 5
RX IN 6
DRIVER OUT 7
RX IN 8
RX IN 9
RX IN 10
DRIVER OUT 11
RXA IN 12
NC 13
3V V
CC
14
G PACKAGE
28-LEAD SSOP
28 NC
27 NC
26 V
–
25 GND
24 DRIVER IN
23 RX OUT
22 DRIVER IN
21 RX OUT
20 RX OUT
19 RX OUT
18 DRIVER IN
17 RXA OUT
16 RS232 ON/OFF
15 GND
NC 1
V
+
C
–
2
3
DRIVER OUT 4
RX IN 5
DRIVER OUT 6
RX IN 7
RX IN 8
RX IN 9
DRIVER OUT 10
RXA IN 11
NC 12
3V V
CC
13
NC 14
N PACKAGE
28-LEAD PLASTIC DIP
T
JMAX
= 150°C,
θ
JA
= 96°C/W
T
JMAX
= 150°C,
θ
JA
= 56°C/W
ORDER PART NUMBER
LT1332CG
Consult factory for Industrial and Military grade parts.
ORDER PART NUMBER
LT1332CN
ELECTRICAL CHARACTERISTICS
PARAMETER
Power Supply
Supply Current I(V
+
)
Supply Current I(V
–
)
Supply Current I(V
CC
)
Supply Current When OFF I(V
CC
)
Supply Current When OFF I(V
+
)
Supply Current When OFF I(V
–
)
CONDITIONS
(Note 3)
(Note 3)
(Note 3)
(Note 4)
(Note 2)
MIN
TYP
0.3
– 0.6
1.0
0.04
0.04
0.10
0.10
MAX
0.8
–1.0
1.5
0.10
0.07
0.20
0.20
UNITS
mA
mA
mA
mA
mA
mA
mA
V
CC
= 3V, V
+
= 8V, V
ON/OFF
= 0.1V
V
CC
= 3V, V
–
= – 8V, V
ON/OFF
= 0.1V
2
U
U
W
W W
U
W
TOP VIEW
28 NC
27
V
–
V
+
C
–
DRIVER OUT
RX IN
DRIVER OUT
RX IN
RX IN
RX IN
DRIVER OUT
1
2
3
4
5
6
7
8
9
TOP VIEW
24 V
–
23 GND
22 DRIVER IN
21 RX OUT
20 DRIVER IN
19 RX OUT
18 RX OUT
17 RX OUT
16 DRIVER IN
15 RXA OUT
14 RS232 ON/OFF
13 GND
26 GND
25 DRIVER IN
24 RX OUT
23 DRIVER IN
22 RX OUT
21 RX OUT
20 RX OUT
19 DRIVER IN
18 RXA OUT
17 RS232 ON/OFF
16 GND
15 NC
RXA IN 10
NC 11
3V V
CC
12
S PACKAGE
24-LEAD PLASTIC SOL
T
JMAX
= 150°C,
θ
JA
= 80°C/W
ORDER PART NUMBER
LT1332CS
q
LT1332
ELECTRICAL CHARACTERISTICS
PARAMETER
Power Supply
ON/OFF Pin Thresholds
ON/OFF Pin Current
Drivers
Output Voltage Swing
Logic Input Voltage Level
Logic Input Current
Output Short-Circuit Current
Output Leakage Current
Driver Output ESD Rating
Slew Rate
Propagation Delay
Receivers
Input Voltage Thresholds
Hysteresis
Input Resistance
Receiver Input ESD Rating
Output Voltage
Output Leakage Current
Output Short-Circuit Current
Propagation Delay
(Note 2)
MIN
q
q
q
q
q
q
q
q
q
CONDITIONS
Input Low Level (Device Shut Down)
Input High Level (Device Enabled)
0V
≤
V
ON/OFF
≤
5V
Positive
Negative
Input Low Level (V
OUT
= High)
Input High Level (V
OUT
= Low)
0.8V
≤
V
IN
≤
2.0V
V
OUT
= 0V
SHUTDOWN V
OUT
=
±30V,
V
ON/OFF
= 0.1V
Human Body Model Discharge
R
L
= 3k, C
L
= 51pF
R
L
= 3k, C
L
= 2500pF
Output Transition t
PHL
High to Low (Note 5)
Output Transition t
PLH
Low to High
Input Low Threshold (V
OUT
= High)
Input High Threshold (V
OUT
= Low)
q
TYP
0.7
0.6
MAX
0.3
80
UNITS
V
V
µA
V
V
V
V
µA
mA
µA
kV
V/µs
V/µs
µs
µs
V
V
V
kΩ
kV
V
V
µA
mA
mA
µs
µs
1.3
–15
5.0
R
L
= 3k to GND
2.0
4
6.6
– 7.0
1.4
1.4
5
±17
10
±10
15
6
0.6
0.5
1.3
1.7
0.4
5
±10
0.2
2.9
1
–4
4
1
0.6
– 5.0
0.8
20
100
30
1.3
1.3
0.8
0.1
3
2.4
1.0
7
0.4
10
–2
3
3
Human Body Model Discharge
Output Low, I
OUT
= – 500µA
Output High, I
OUT
= 100µA (V
CC
= 3V)
SHUTDOWN (Note 6) 0
≤
V
OUT
≤
V
CC
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
2.7
2
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 the device may be impaired.
Note 2:
Testing is done at V
CC
= 3V, V
+
= 8V, V
–
= – 8V, and
V
ON/OFF
= 3V.
Note 3:
Supply current is measured with all driver inputs tied high.
Note 4:
Supply current measurements in SHUTDOWN are performed with
V
ON/OFF
= 0.1V, V
+
= 0V, V
–
= 0V.
Note 5:
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
PHL
= 1.4V to 0V and t
PLH
= 1.4V to 0V).
Note 6:
Receiver RXA (Pins 10 and 15, S Package) remains functioning in
SHUTDOWN.
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
LH
= 1.3V to 2.4V and t
HL
= 1.7V
to 0.8V).
3
LT1332
TYPICAL PERFOR A CE CHARACTERISTICS
Unloaded Supply Current
vs Temperature
1.6
1.4
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
1.2
1.0
I(V
–
)
DRIVER OUTPUTS HIGH
I(V
CC
)
12
10
8
6
4
2
I(V
–
)
I(V
+
)
THRESHOLD VOLTAGE (V)
0.8
0.6
0.4
0.2
0
–50 –25
0
75
50
25
TEMPERATURE (˚C)
100
125
I(V
+
)
DRIVER OUTPUTS LOW
Leakage Current in Shutdown
vs Temperature
150
125
LEAKAGE CURRENT (µA)
100
LEAKAGE CURRENT (µA)
I(V
+
) = 8V
I(V
–
) = – 8V
SHORT-CIRCUIT CURRENT (mA)
100
75
50
I(V
CC
) = 3V
25
0
–50 –25
50
25
75
0
TEMPERATURE (˚C)
LT1027 • TPC04
Slew Rate vs Load Capacitance
15
14
13
SR
–
R
L
= 3k
8
6
DRIVER OUTPUT VOLTAGE (V)
SLEW RATE (V/µs)
12
11
10
9
8
7
6
5
4
0
500
1000 1500 2000
CAPACITANCE (pF)
2500
3000
SR
+
4
2
0
–2
–4
–6
V
+
= 8V
V
–
= –8V
V
CC
= 3V
SHORT-CIRCUIT CURRENT (mA)
4
U W
LT1332 • TPC01
Supply Current vs Data Rate
16
14
R
L
= 3k
C
L
= 2500pF
ALL DRIVERS LOADED
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
ON/OFF Threshold vs Temperature
I(V
CC
)
0
20 40 60 80 100 120 140 160 180 200
DATA RATE (k BAUD)
LT1332 • TPC02
0
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1332 • TPC03
Driver Leakage in Shutdown
vs Temperature
30
25
Driver Short-Circuit Current
vs Temperature
I
SC+
20
15
10
5
0
–50 –25
I
SC–
10
V
OUT
= 30V
1
V
OUT
= –30V
100
125
0.1
–50
–25
0
50
25
75
TEMPERATURE (°C)
100
125
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1332 • TPC06
LT1332 • TPC05
Driver Output Voltage
vs Temperature
30
INPUT LOW
Receiver Short-Circuit Current
vs Temperature
25
20
15
10
I
SC+
5
0
–50 –25
I
SC–
INPUT HIGH
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1332 • TPC08
–8
– 50 – 25
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1332 • TPC09
LT1332 • TPC07
LT1332
TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Thresholds
vs Supply Voltage
5
RECEIVER INPUT THRESHOLD (V)
RECEIVER INPUT THRESHOLD (V)
2.5
V
CC
= 3V
SUPPLY VOLTAGE/RECEIVER OUTPUT (V)
4
V
TH
HIGH
3
2
V
TH
LOW
1
0
2.0
2.5
3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
LT1332 • TPC10
Receiver Output Waveforms
INPUT
5V/DIV
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
10V/DIV
RX OUTPUT
C
L
= 50pF
2V/DIV
INPUT
5V/DIV
PI FU CTIO S
V
CC
:
Input Supply Pin. V
CC
can vary from 2V to 6V to
accommodate a wide range of logic levels, yet the system
still responds correctly to RS232 signals. Supply current
drops to 40µA in the SHUTDOWN mode. This pin should
be decoupled with a 0.1µF ceramic capacitor.
GND:
Ground Pins. Pins 13 and 23 (S Package) must both
be grounded for proper operation.
ON/OFF:
Controls the operation mode of the device and
is CMOS compatible. A logic low puts the device in the
SHUTDOWN mode which reduces input supply current
to 40µA and places all of the drivers and four of the
receivers in a high impedance state. A logic high fully
enables the device.
V
+
:
Positive Supply Input (RS232 Drivers). V
+
should
be greater than 6.5V and less than 13.2V to assure valid
RS232 output signals. An additional decoupling ca-
pacitor may be required if the V
+
generator is located far
away from the LT1332.
V
–
:
Negative Supply Pin (RS232 Drivers). This pin re-
quires an external capacitor. When the device is powered
from a switching regulator, the filter capacitor should be
selected based on the maximum tolerable ripple for the
specified minimum regulator on time. For some low
frequency Burst Mode
TM
regulators, the filter capacitor
should be relatively large (C
≥
10µF). Low ESR tantalum
Burst Mode
TM
is a trademark of Linear Technology Corporation
U W
5.5 6.0
Receiver Input Thresholds
vs Temperature
0.6
0.5
0.4
0.3
0.2
0.1
Receiver Output Voltage
vs Supply Voltage
RECEIVER
OUTPUT LOW
SINKING 500µA
RECEIVER
OUTPUT LOW
SINKING 250µA
2.0
V
TH
HIGH
1.5
V
TH
LOW
1.0
RECEIVER
OUTPUT HIGH
(V
CC
– V
OUT
)
SOURCING
0.5
0
–50 –25
0
25 50
75 100 125 150
TEMPERATURE (°C)
LT1332 • TPC11
0
2.0
2.5
3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
5.5
6.0
LT1332 • TPC12
Driver Output Waveforms
DRIVER
OUTPUT
R
L
= 3k
10V/DIV
LT1332 • TPC13
LT1332 • TPC13
U
U
U
5
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