LT1237CNW Linear Technology, LT1237CNW Datasheet - Page 7

• Manufacturer Part Number: LT1237CNW
• Description: IC TXRX 5V RS232 ADV LOPWR 28DIP
• Manufacturer: Linear Technology
• Type: Transceiverr

Specifications of LT1237CNW

• Number Of Drivers/receivers: 3/5
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Through Hole
• Package / Case: 28-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LT1237CN; LT1237CN

PACKAGE DESCRIPTIO
Storage Capacitor Selection
The V
fully to insure low ripple and stable operation. The LT1237
charge pump operates in a power efficient Burst Mode
operation. When storage capacitor voltage drops below a
preset threshold, the oscillator is gated on until V
are boosted up to levels exceeding a second threshold.
The oscillator then turns off, and current is supplied from
the V
The V
operation. It is therefore important to insure lower V
ripple than V
pump will result. Proper operation is insured in most
applications by choosing the V
least 5 times the V
heavily loaded than V
The V
ripple when the drivers are loaded, forcing the charge
pump into continuous mode. A minimum value 0.1 F is
suggested.
A
PPLICATI
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
+
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
+
–
–
and V
(15.240 – 15.875)
and V
filter capacitor should be selected to obtain low
potential is monitored to control charge pump
0.600 – 0.625
15.87
0.625
(0.229 – 0.381)
0.009 – 0.015
–0.015
+0.889
–0.381
+0.035
–
–
–
storage capacitors.
ripple, or erratic operation of the charge
storage capacitors must be chosen care-
O
(0.381)
0.015
–
MIN
U
**
0.005 – 0.009
(0.13 – 0.22)
*
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
filter capacitor value. If V
–
(3.810 0.127)
0.150 0.005
S
, a larger ratio may be needed.
(3.175)
0.125
MIN
I FOR ATIO
U
0.205 – 0.212**
0.022 – 0.037
(5.20 – 5.38)
(0.55 – 0.95)
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.
+
(2.540 0.254)
0.100 0.010
filter capacitor to be at
(0.889 – 2.032)
0.035 – 0.080
W
U
(1.143 – 1.651)
0 – 8
0.045 – 0.065
Dimensions in inches (millimeters) unless otherwise noted.
0.0256
(0.65)
BSC
28-Lead Plastic SSOP (0.209)
28-Lead PDIP (Wide 0.600)
+
U
+
0.010 – 0.015
(0.25 – 0.38)
(LTC DWG # 05-08-1520)
is more
(LTC DWG # 05-08-1640)
and V
(0.457 0.076)
0.018 0.003
NW Package
G Package
TM
–
+
Do not attempt to reduce V
is in discontinuous Burst Mode operation. The ripple in
this mode is determined by internal comparator thresh-
olds. 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 operat-
ing 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 informa-
tion 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 con-
sumption in driver disable mode is 3mA from V
Burst Mode is a trademark of Linear Technology Corporation
0.002 – 0.008
(0.05 – 0.21)
(1.778)
0.070
(12.827 – 14.224)
0.068 – 0.078
(1.73 – 1.99)
TYP
0.505 – 0.560*
28
1
28
1 2 3 4 5 6 7 8 9 10 11 12
27
27
2
26
25
26
3
24
0.397 – 0.407*
(10.07 – 10.33)
23
25
4
22 21 20 19 18 17 16 15
24
5
–
ripple when the charge pump
23
6
(36.957)
1.455*
MAX
22
7
13
14
21
8
0.301 – 0.311
(7.65 – 7.90)
20
G28 SSOP 0694
9
19
10
18
11
17
12
LT1237
13
16
CC
N28 1197
15
14
.
7