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PDF LTC2802 Data sheet ( Hoja de datos )
| Número de pieza | LTC2802 | |
| Descripción | (LTC2801 - LTC2804) Single and Dual Transceivers | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC2802 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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LTC2801/LTC2802/
LTC2803/LTC2804
1.8V to 5.5V RS-232
Single and Dual Transceivers
FEATURES
DESCRIPTIO
■ 1.8V to 5.5V Supply Voltage
■ Single and Dual Transceivers
■ High-Speed Operation
1Mbps for 250pF/3kΩ Load (LTC2802, LTC2804)
250kbps for 1nF/3kΩ Load
100kbps for 2.5nF/3kΩ TIA/EIA-232-F Load
■ Low-Power 1μA Shutdown and 15μA Receivers-
Active Modes
■ No Damage or Latch-Up to ±10kV ESD on RS-232
Interface
■ Logic Supply Pin for Easy Level-Shifting to UART or
Microprocessor
■ Low-Latency Output Enable Allows Line Sharing and
Half-Duplex Operation
■ True RS-232 Compliant Output Levels
■ Small Footprint:
LTC2801/LTC2802 4mm × 3mm DFN Package
LTC2803/LTC2804 Narrow SSOP-16 and
5mm × 3mm DFN Packages
U
APPLICATIO S
■ Battery-Powered Systems
■ Computers and Consumer Electronics
■ Diagnostic Ports
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
The LTC®2801/LTC2802/LTC2803/LTC2804 are single and
dual RS-232 transceivers in narrow SSOP and chip-scale
DFN packages. All operate over a supply range of 1.8V to
5.5V, which permits operation directly from two alkaline,
NiCd or NiMH cells. An integrated DC-to-DC converter
generates power supplies for driving RS-232 levels. A
logic supply pin allows easy interfacing with different logic
levels independent of the DC-DC supply.
These parts are compatible with the TIA/EIA-232-F stan-
dard. Driver outputs are protected from overload and can
be shorted to ground or up to ±15V without damage. To
extend battery life, receivers can be kept active, operating
at reduced speed, with only 15μA current. In shutdown
mode, current is further reduced to 1μA. Line sharing and
half-duplex operation are also supported.
U
PRODUCT SELECTIO GUIDE
PART NUMBER
LTC2801
LTC2802
LTC2803
LTC2803-1
LTC2804
LTC2804-1
DRIVERS
1
1
2
2
2
2
RECEIVERS
1
1
2
2
2
2
PACKAGE
12-Lead DFN
12-Lead DFN
16-Lead DFN
16-Lead SSOP
16-Lead DFN
16-Lead SSOP
TYPICAL APPLICATIO
1.8V TO 5.5V
L1
10µH
C4
1µF
OFF ON
VCC
VL
PS
MODE
TIN
LTC2802
SW
CAP
TOUT
ROUT
RIN
GND VDD
VEE
C2
1µF
C1
220nF
C3
1µF
2801 TA01a
DataSheet4 U .com
LTC2802 at 1.8V and 1Mbps
2V/DIV
TIN
5V/DIV
TOUT
2V/DIV
ROUT
VCC = VL = 1.8V 400ns/DIV
WRAPPING DATA
TOUT LOAD = 250pF + RIN
ROUT LOAD = 150pF
2801 TA01b
2801234f
1
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TEST CIRCUITS
TIN RL
TIN tr, tf ≤ 40ns
LTC2801/LTC2802/
LTC2803/LTC2804
TOUT
TIN
CL
TOUT
6V
SR(D) =
tTHL or tTLH
3V
–3V
tTHL
Figure 1. Driver Slew Rate Measurement
VL
0V
tTLH
3V VOHD
–3V VOLD
2801F02
TIN RL
TIN tr, tf ≤ 40ns
TOUT
CL
VL
TIN 1/2 VL
1/2 VL
0V
tPHLD
tPLHD
VOHD
TOUT
0V
0V
tSKEWD = |tPHLD – tPLHD|
VOLD
2801F02
Figure 2. Driver Timing Measurement
RIN
RIN tr, tf ≤ 40ns
ROUT
CL
RIN
ROUT
1.5V
tPHLR
1.5V
tPLHR
1/2 VL
tSKEWR = |tPHLR – tPLHR|
3V
–3V
VOHR
1/2 VL
VOLR
2801F03
Figure 3. Receiver Timing Measurement
0 OR VL
DataSheet4 U .com
MODE
RL
MODE tr, tf ≤ 40ns
TOUT
CL
MODE 1/2 VL
TOUT
tPZHD
TOUT
tPZLD
5V
–5V
Figure 4. Driver Enable/Disable Times
1/2 VL
VL
tPHZD
tPLZD
0V
VOHD – 0.5V VOHD
0V
0V
VOLD + 0.5V VOLD
2801F04
2801234f
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5 Page 
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LTC2801/LTC2802/
LTC2803/LTC2804
APPLICATIO S I FOR ATIO
Table 3. Recommended Inductors
PART
NUMBER
ISAT
(mA)
MAX DCR
(Ω)
SIZE
(mm)
MANUFACTURER
LQH2MCN100K02L 225
1.2 2x1.6x0.95 Murata
www.murata.com
LBC2016T100K
245 0.85 2x1.6x1.6 Taiyo Yuden
www.t-yuden.com
FSLB2520-100K 220 1.1 2.5x2x1.6 Toko
www.tokoam.com
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
the LTC2801 family. X5R and X7R (preferred) types are
recommended because their ESR is low and they retain their
capacitance over relatively wide voltage and temperature
ranges. Use a voltage rating of at least 10V.
Table 4. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
URL
Murata
www.murata.com
TDK www.tdk.com
Taiyo Yuden
www.t-yuden.com
AVX www.avxcorp.com
Kemet
www.kemet.com
Inrush Current and Supply Overshoot Precaution
In certain applications, such as battery-operated and
wall-adapter devices, fast supply slew rates are generated
when power is connected. If VCC’s voltage is greater than
4.5V and its rise time is faster than 10μs, the pins VDD
and SW can exceed their ABS MAX values during start-
up. When supply voltage is applied to VCC, the voltage
difference between VCC and VDD generates inrush current
4.5V TO 5.5V
L1
10µH
C1
220nF
R1
1Ω
1/8W
INRUSH
CURRENT
VCC
C4
1µF
SCALE R1 WITH C1, C2, 1/C4
C2
1µF
SW
VDD
CAP
GND
Figure 8. Supply Overshoot Protection for Input
Supplies of 4.5V or Higher
2801F08
DataSheet4 U .com
flowing through inductor L1 and capacitors C1, C2. The
peak inrush current must not exceed 2A. To avoid this
condition, add a 1Ω resistor as shown in Figure 8. This
precaution is not relevant for supply voltages below 4.5V
or rise times longer than 10μs.
Board Layout
The board layout should minimize the length and area of
the SW and CAP traces. Suggested compact layouts for
the LTC2801 family are shown in Figure 9 (a) and (b).
VL
GND C5
TOP VIEW
= VIA
C1 GND
GND
C2 L1
GND
C3
VCC
GND
C4
VL
C5
GND
C1 GND
GND
C2 L1
VCC
GND
C4
GND
C3
TOP VIEW
= VIA
2801F09
Figure 9. Recommended Board Layouts for (a) Single and
(b) Dual Transceiver Parts
2801234f
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC2802.PDF ] | |
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