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LT1237 5V RS232 Transceiver with Advanced Power Management and One Receiver Active in SHUTDOWN
FEATURES
s s s s s s s s s s s s
DESCRIPTIO
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One Receiver Remains Active While in SHUTDOWN ESD Protection over 10kV Uses Small Capacitors: 0.1F, 0.2F, 1.0F 60A Supply Current in SHUTDOWN Pin-Compatible with LT1137A 120kBaud Operation for RL = 3k, CL = 2500pF 250kBaud Operation for RL = 3k, CL = 1000pF CMOS Comparable Low Power 30mW Operates from a Single 5V Supply Easy PC Layout - Flowthrough Architecture Rugged Bipolar Design Outputs Assume a High Impedance State When Off or Powered Down Absolutely No Latchup Available in SO and SSOP Packages
The LT1237 is an advanced low power three driver, five receiver RS232 transceiver. Included on the chip is a shutdown pin for reducing supply current near zero. During SHUTDOWN one receiver remains active to detect incoming RS232 signals, for example, to wake up a system. The LT1237 is fully compliant with all EIA RS232 specifications. New ESD structures on the chip allow the LT1237 to survive multiple 10kV strikes, eliminating the need for costly TransZorbs(R) on the RS232 line pins. The LT1237 operates in excess of 120k baud even driving heavy capacitive loads. Two SHUTDOWN modes allow the driver outputs to be shut down separately from the receivers for more versatile control of the RS232 interface. During SHUTDOWN, drivers and receivers assume a high impedance state.
TransZorb is a registered trademark of General Instruments, GSI
APPLICATI
s s
S
Notebook Computers Palmtop Computers
TYPICAL APPLICATI
V+ 1.0F 2 x 0.1F 5V VCC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 LT1237
28 27 25 24 23 22 21 20 19 18 17 16 15 26
V- 0.1F
RECEIVER OUTPUT CL = 50pF DRIVER OUTPUT RL = 3k CL = 2500pF
DRIVER 1 IN RX1 OUT DRIVER 2 IN RX2 OUT RX3 OUT RX4 OUT DRIVER 3 IN RX5 OUT (LOW-Q) GND DRIVER DISABLE RING DETECT IN CONTROLLER OR PROCESSOR
R
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
+
+
2 x 0.1F
TO LOGIC
INPUT
SHUTDOWN CONTROL OUT
LT1237 TA01
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Output Waveforms
1237 TA02
+
UO
UO
1
LT1237 ABSOLUTE
(Note 1)
TOP VIEW
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
V+ C1+ C1- 1 3 4 28 V- 27 C2 - 26 C2+ 25 DR1 IN 24 RX1 OUT 23 DR2 IN 22 RX2 OUT 21 RX3 OUT 20 RX4 OUT 19 DR3 IN RX5 OUT 18 (LOW-Q) 17 GND 16 DRIVER DISABLE 15 NC N PACKAGE 28-LEAD PLASTIC DIP G PACKAGE 28-LEAD SSOP
Supply Voltage (VCC) ................................................ 6V V + ........................................................................ 13.2V V - ...................................................................... -13.2V Input Voltage Driver ........................................................... V - to V + Receiver ............................................... - 30V to 30V Output Voltage Driver .................................................... - 30V to 30V Receiver .................................... - 0.3V to VCC + 0.3V Short Circuit Duration V + ................................................................... 30 sec V - ................................................................... 30 sec Driver Output .............................................. Indefinite Receiver Output .......................................... Indefinite Operating Temperature Range LT1237I ............................................. - 40C to 85C LT1237C ................................................. 0C to 70C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LT1237IJ LT1237IN LT1237CJ LT1237CN LT1237CS LT1237CG
5V VCC 2
DR1 OUT 5 RX1 IN 6 DR2 OUT 7 RX2 IN 8 RX3 IN 9 RX4 IN 10 DR3 OUT 11 RX5 IN 12 (LOW-Q) ON/OFF 13 NC 14 J PACKAGE 28-LEAD CERAMIC DIP S PACKAGE 28-LEAD SOL
TJMAX = 150C, JA = 62C/ W (J) TJMAX = 150C, JA = 56C/ W (N) TJMAX = 150C, JA = 85C/ W (S) TJMAX = 150C, JA = 96C/ W (G)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER Power Supply Generator V + Output V - Output Supply Current (VCC) Supply Current when OFF (VCC) 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 7.9 -7 6 6 0.06 3.00 2 0.8 -15 0.8 -10 130 1.2 1.6 1.4 1.4 MAX UNITS V V mA mA mA mA ms V V A V V A kHz
TA = 25C (Note 3)
q
SHUTDOWN (Note 4) DRIVER DISABLE C1 = C2 = 0.2F, C + = 1.0F, C - = 0.1F Input Low Level (Device SHUTDOWN) Input High Level (Device Enabled) 0V VON/OFF 5V Input Low Level (Drivers Enabled) Input High Level (Drivers Disabled) 0V VDRIVER DISABLE 5V Driver Outputs Loaded RL = 3k
q
12 14 0.15
q q q q q q
2.4 80 2.4 500
2
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W
U
U
WW
W
LT1237
ELECTRICAL CHARACTERISTICS
PARAMETER Any Driver Output Voltage Swing Logic Input Voltage Level Logic Input Current Output Short-Circuit Current Output Leakage Current Data Rate Slew Rate Propagation Delay Any Receiver Input Voltage Thresholds Hysteresis Input Resistance Output Leakage Current Receivers 1, 2, 3, 4 Output Voltage Output Short-Circuit Current Propagation Delay Receiver 5 (LOW ISUPPLY RX) Output Voltage Output Short-Circuit Current Propagation Delay CONDITIONS Load = 3k to GND
(Note 2)
MIN Positive Negative
q q q q q
TYP 7.5 - 6.3 1.4 1.4 5 17 10
MAX
UNITS V V V V A mA A kBaud kBaud V/s V/s s s V V V k A V V mA mA ns ns V V mA mA s s
5.0
Input Low Level (VOUT = High) Input High Level (VOUT = Low) 0.8V VIN 2V VOUT = 0V SHUTDOWN VOUT = 30V (Note 4) RL = 3k, CL = 2500pF RL = 3k, CL = 1000pF RL = 3k, CL = 51pF RL = 3k, CL = 2500pF Output Transition tHL High to Low (Note 5) Output Transition tLH Low to High Input Low Threshold (VOUT = High) Input High Threshold (VOUT = Low)
- 5.0 0.8 20 100
2.0 9
q
120 250 4 15 7 0.6 0.5 1.3 1.7 0.4 5 1 0.2 4.2 - 20 20 250 350 0.2 4.2 -4 4 1.0 0.6 30 1.3 1.3
0.8
q
VIN = 10V SHUTDOWN (Note 4) 0 VOUT VCC Output Low, IOUT = - 1.6mA Output High, IOUT = 160A (VCC = 5V) Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Output Transition tHL High to Low (Note 6) Output Transition tLH Low to High Output Low, IOUT = - 500A Output High, IOUT = 160A (VCC = 5V) Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Output Transition tHL High to Low (Note 6) Output Transition tLH Low to High
0.1 3
q q q
2.4 1.0 7 10 0.4
3.5 - 10 10
600 600 0.4
q q
3.5 -2 2
3 3
The q denotes specifications which apply over the operating temperature range (0C TA 70C for commercial grade, and - 40C TA 85C for industrial grade). Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Testing done at VCC = 5V and VON/OFF = 3V, unless otherwise specified. Note 3: Supply current is measured as the average over several charge pump burst cycles. C + = 1.0F, C - = 0.1F, C1 = C2 = 0.2F. All outputs are open, with all driver inputs tied high.
Note 4: Measurements in SHUTDOWN are performed with VON/OFF 0.1V. Supply current measurements using DRIVER DISABLE are performed with VDRIVER DISABLE 3V. Note 5: For driver delay measurements, RL = 3k and CL = 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 tLH = 1.4V to 0V). Note 6: For receiver delay measurements, CL = 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 2.4V and tLH = 1.7V to 0.8V).
3
LT1237
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output Voltage
10 8
DRIVER OUTPUT VOLTAGE (V)
RL = 3k
OUTPUT HIGH
VCC = 5V
THRESHOLD VOLTAGE (V)
6 4 2 0 -2 -4 -6 -8 -10 -55 -25 OUTPUT LOW
VCC = 4.5V
2.25 2.00 1.75 1.50 1.25 1.00 0.75 INPUT LOW INPUT HIGH
SUPPLY CURRENT (mA)
VCC = 4.5V VCC = 5V
50 25 0 75 TEMPERATURE (C)
Supply Current in SHUTDOWN
150 125
SUPPLY CURRENT (A)
5
THRESHOLD VOLTAGE (V)
SUPPLY CURRENT (mA)
100 75 50 25 0 -55 -25
50 25 75 0 TEMPERATURE (C)
On/Off Thresholds
3.0 2.5
THRESHOLD VOLTAGE (V)
LEAKAGE CURRENT ( A)
SUPPLY CURRENT (mA)
2.0 1.5 1.0
ON THRESHOLD
OFF THRESHOLD 0.5 0 -55 -25
50 25 75 0 TEMPERATURE (C)
4
UW
100
1237 G01
Receiver Input Thresholds
3.00 2.75 2.50
Supply Current vs Data Rate
80 70 60 50 40 30 20 10 3DRIVERS ACTIVE RL = 3k CL = 2500pF
125
0.50 -55 -25
50 25 0 75 TEMPERATURE (C)
100
125
0 0 25 75 50 100 DATA RATE (kBAUD) 125 150
1237 G02
1237 G03
Supply Current in DRIVER DISABLE
3.0 2.5 2.0 1.5 1.0 0.5
Driver Disable Threshold
4
3
2
1
100
125
0 -55 -25
50 25 0 75 TEMPERATURE (C)
100
125
0 -55 -25
50 25 75 0 TEMPERATURE (C)
100
125
1237 G04
1237 G05
1237 G06
Supply Current
40 35 30 25 20 15 10 5
100 125
100
Driver Leakage in SHUTDOWN
3DRIVERS LOADED RL = 3k
10
1DRIVER LOADED RL = 3k
1
VOUT = 30V VOUT = -30V
NO LOAD
0 -55 -25
50 25 0 75 TEMPERATURE (C)
100
125
0.1 -55 -25
50 25 0 75 TEMPERATURE (C)
100
125
1237 G07
1237 G08
1237 G09
LT1237
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Short-Circuit Current
30
SHORT-CIRCUIT CURRENT (mA)
50
SHORT-CIRCUIT CURRENT (mA)
25 ISC + 20 15 ISC - 10 5 0 -55 -25
50 25 75 0 TEMPERATURE (C)
Receiver Output Waveforms
RX5 OUTPUT CL = 50pF RX1 TO RX4 OUTPUT CL = 50pF DRIVER OUTPUT RL = 3k CL = 2500pF DRIVER OUTPUT RL = 3k INPUT
INPUT
PI FU CTIO S
VCC: 5V Input Supply Pin. This pin should be decoupled with a 0.1F ceramic capacitor close to the package pin. Insufficient supply bypassing can result in low output drive levels and erratic charge pump operation. GND: Ground Pin. ON/OFF: TTL/CMOS Compatible Operating Mode Control. A logic low puts the device in the low power SHUTDOWN mode. All three drivers and four receivers (RX1, RX2, RX3, and RX4) assume a high impedance output state in SHUTDOWN. Only receiver RX5 remains active while the transceiver is in SHUTDOWN. The transceiver consumes only 60A of supply current while in SHUTDOWN. A logic high fully enables the transceiver. DRIVER DISABLE: This pin provides an alternate control for the charge pump and RS232 drivers. A logic high on this pin shuts down the charge pump and places all driver outputs in a high impedance state. All five receivers remain active under these conditions. Floating the driver disable pin or driving it to a logic low level fully enables the transceiver. A logic low on the On/Off pin supersedes the state of the Driver Disable pin. Supply current drops to 3mA when in DRIVER DISABLE mode. V +: Positive Supply Output (RS232 Drivers). V + 2VCC - 1.5V. This pin requires an external charge storage capacitor C 1.0F, tied to ground or VCC. Larger value capacitors may be used to reduce supply ripple. The ratio of the capacitors on V + and V - should be greater than 5 to 1.
UW
Receiver Short-Circuit Current
40 RX1 TO RX4 ISC - 30 RX1 TO RX4 ISC + RX5 ISC -
20
10 RX5 ISC + 0 -55 -25 50 25 0 75 TEMPERATURE (C) 125
100
125
100
1237 G10
1237 G11
Driver Output Waveforms
1237 G12
1237 G13
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5
LT1237
PI FU CTIO S
V -: Negative Supply Output (RS232 Drivers). V - - (2VCC - 2.5V). This pin requires an external charge storage capacitor C 0.1F. See the Applications Information section for guidance in choosing filter capacitors for V + and V -. C1+, C1-, C2+, C2 -: Commutating Capacitor Inputs, require two external capacitors C 0.2F: one from C1+ to C1-, and another from C2 + to C2 -. The capacitor's effective series resistance should be less than 2. For C 1F, low ESR tantalum capacitors work well in this application, although small value ceramic capacitors may be used with a minimal reduction in charge pump compliance. DRIVER IN: RS232 Driver Input Pins. These inputs are TTL/CMOS compatible. Inputs should not be allowed to float. Tie unused inputs to VCC. DRIVER OUT: Driver Outputs at RS232 Voltage Levels. Driver output swing meets RS232 levels for loads up to 3k. Slew rates are controlled for lightly loaded lines. Output current capability is sufficient for load conditions up to 2500pF. Outputs are in a high impedance state when in SHUTDOWN mode, VCC = 0V, or when the driver disable pin is active. Outputs are fully short-circuit protected from V - + 30V to V + - 30V. Applying higher voltages will not damage the device if the overdrive is moderately current limited. 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. RX IN: Receiver Inputs. 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. Each receiver provides 0.4V of hysteresis for noise immunity. Open receiver inputs assume a logic low state. RX OUT: Receiver Outputs with TTL/CMOS Voltage Levels. Outputs RX1, RX2, RX3, and RX4 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 protected to ground or VCC with the power on, off, or in SHUTDOWN mode. LOW Q-CURRENT RX IN: Low Power Receiver Input. This special receiver remains active when the part is in SHUTDOWN mode, consuming typically 60A. This receiver has the same 5k input impedance and 10kV ESD protection characteristics as the other receivers. LOW Q-CURRENT RX OUT: Low Power Receiver Output. This pin produces the same TTL/CMOS output voltage levels as receivers RX1, RX2, RX3, and RX4 with slightly decreased speed and short-circuit current. Data rates to 120k baud are supported by this receiver.
ESD PROTECTIO
0.2F DRIVER 1 OUT RX1 IN DRIVER 2 OUT RS232 LINE PINS PROTECTED TO 10kV RX2 IN RX3 IN RX4 IN DRIVER 3 OUT RX5 IN (LOW-Q) ON/OFF
4 5 6 7 8 9 10 11 12 13 14
25 24 23 22 21 20 19 18 17 16 15
DRIVER 1 IN RX1 OUT DRIVER 2 IN RX2 OUT RX3 OUT RX4 OUT DRIVER 3 IN RX5 OUT (LOW-Q) GND DRIVER DISABLE
1237 TC01
6
+
1F
0.1F
+
3
26
+
The RS232 line inputs of the LT1237 have on-chip protection from ESD transients up to 10kV. The protection structures act to divert the static discharge safely to system ground. In order for the ESD protection to function effectively, the power supply and ground pins of the LT1237 must be connected to ground through low impedances. The power supply decoupling capacitors and charge pump storage capacitors provide this low impedance in normal application of the circuit. The only constraint is that low ESR capacitors must be used for bypassing and charge storage. ESD testing must be done with pins VCC, VL, V +, V -, and GND shorted to ground or connected with low ESR capacitors.
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ESD Test Circuit
1 V+ 5V VCC 2 28 LT1237 27 V- 0.1F 0.2F
+
+
LT1237
APPLICATI S I FOR ATIO
Storage Capacitor Selection The V + and V - storage capacitors must be chosen carefully to insure low ripple and stable operation. The LT1237 charge pump operates in a power efficient Burst ModeTM. When storage capacitor voltage drops below a preset threshold, the oscillator is gated on until V+ and V - are boosted up to levels exceeding a second threshold. The oscillator then turns off, and current is supplied from the V+ and V - storage capacitors. The V - potential is monitored to control charge pump operation. It is therefore important to insure lower V + ripple than V - ripple, or erratic operation of the charge pump will result. Proper operation is insured in most applications by choosing the V+ filter capacitor to be at least 5 times the V - filter capacitor value. If V + is more heavily loaded than V -, a larger ratio may be needed. The V - filter capacitor should be selected to obtain low ripple when the drivers are loaded, forcing the charge pump into continuous mode. A minimum value 0.1F is suggested.
Typical Mouse Driving Application
2 x 0.1F V+ LOGIC (1) DCD DSR RX RTS OPTICS V- TX CTS DTR (5) (9) RI DRIVER 1 OUT RX1 IN DRIVER 2 OUT RX2 IN RX3 IN
4 5 6 7 8 9
25 DRIVER 1 IN 24 RX1 OUT 23 DRIVER 2 IN 22 RX2 OUT 21 RX3 OUT 20 RX4 OUT 19 DRIVER 3 IN 18 RX5 OUT (LOW-Q) 17 GND 16 DRIVER DISABLE 15
RX4 IN 10 DRIVER 3 OUT 11 RX5 IN (LOW-Q) 12 ON/OFF 13 14
DB9
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
+
MOUSE
+
3
26
LOGIC "0" LOGIC "0"
MOUSE DATA
LOGIC "1"
1237 TA03
+
U
Do not attempt to reduce V - ripple when the charge pump is in discontinuous Burst ModeTM operation. The ripple in this mode is determined by internal comparator thresholds. Larger storage capacitor values increase the burst period, and do not reduce ripple amplitude. Power Saving Operational Modes The LT1237 has both SHUTDOWN and DRIVER DISABLE operating modes. These operating modes can optimize power consumption based upon applications needs. The On/Off shutdown control turns off all circuitry except for Low-Q RX5. When RX5 detects a signal, this information can be used to wake up the system for full operation. If more than one line must be monitored, the DRIVER DISABLE mode provides a power efficient operating option. The DRIVER DISABLE mode turns off the charge pump and RS232 drivers, but keeps all five receivers active. Power consumption in DRIVER DISABLE mode is 3mA from VCC.
Burst Mode is a trademark of Linear Technology Corporation
W
U
UO
V+ 1.0F 5V VCC
1 2 LT1237
28 27
V- 2 x 0.1F 0.1F
7
LT1237
PACKAGE DESCRIPTIO
0.590 - 0.620 (14.99 - 15.75) 0.020 - 0.070 (0.508 - 1.778) 95 5
0.180 (4.572) MAX
(
0.008 - 0.012 (0.203 - 0.305) +0.025 0.685 -0.060 +0.635 17.40 -1.524
)
0.125 (3.175) MIN 0.060 - 0.100 (1.524 - 2.540)
0.600 - 0.625 (15.240 - 15.875)
0.020 (0.508) TYP
0.130 0.005 (3.302 0.127)
0.045 - 0.055 (1.143 - 1.651)
95 5 0.009 - 0.015 (0.229 - 0.381) +0.025 0.625 -0.015 +0.635 15.87 -0.381
0.020 (0.508) MIN
(
)
0.125 (3.175) MIN
0.035 - 0.080 (0.889 - 2.032) 0.100 0.010 (2.540 0.254)
0.291 - 0.299 (7.391 - 7.595) 0.005 (0.127) RAD MIN 0.010 - 0.029 x 45 (0.254 - 0.737) 0 - 8 TYP 0.050 0.014 - 0.019 0.009 - 0.013 (1.270) (0.356 - 0.482) (0.229 - 0.330) SEE NOTE TYP 0.016 - 0.050 (0.406 - 1.270) NOTE: 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. 0.093 - 0.104 (2.362 - 2.642)
0.205 - 0.212 (5.20 - 5.38) PARTING LINE 0.005 - 0.009 (0.13 - 0.22) 0.022 - 0.037 (0.55 - 0.95)
0 - 8 0.0256 (0.65) BSC 0.010 - 0.015 (0.25 - 0.38) 0.045 (1.14) 0.002 - 0.008 (0.05 - 0.21)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
U
Dimensions in inches (millimeters) unless otherwise noted. J Package 28-Lead Ceramic DIP
0.225 (5.715) MAX 0.025 (0.635) RAD TYP 86 - 94 0.514 - 0.526 (13.05 - 13.36) TYP MAX 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23
1.490 (37.85) MAX 22 21 20 19 18 17 16 15
0.055 0.005 (1.397 0.127) 0.018 0.002 (0.457 0.051)
0.100 0.010 (2.540 0.254)
N Package 28-Lead Plastic DIP
0.070 (1.778) TYP 28 27 26 25 24 23 1.455 (36.957) MAX 22 21
20
19
18
17
16
15
0.505 - 0.560 (12.827 - 14.224) 0.018 0.003 (0.457 0.076)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
S Package 28-Lead SOL
0.037 - 0.045 (0.940 - 1.143) 0.697 - 0.712 (17.70 - 18.08) 28 27 26 25 24 23 22 21 20 19 18 17 16 15
0.004 - 0.012 (0.102 - 0.305)
SEE NOTE
0.394 - 0.419 (10.007 - 10.643)
1
2
3
4
5
6
7
8
9 10 11 12 13 14
G Package 28-Lead SSOP
0.397 - 0.407 (10.07 - 10.33) 0.066 - 0.070 (1.68 - 1.78) 0.068 - 0.078 (1.73 - 1.99)
28 27 26 25 24 23 22 21 20 19 18 17 16 15
0.301 - 0.311 (7.65 - 7.90)
0.045 (1.14)
LT/GP 1292 10K REV 0
(c) LINEAR TECHNOLOGY CORPORATION 1992

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