MAX3293_11 [MAXIM]
20Mbps, +3.3V, SOT23 RS-485/ RS-422 Transmitters; 20Mbps的， + 3.3V ， SOT23 RS - 485 / RS - 422发射器
| 型号： | MAX3293_11 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 20Mbps, +3.3V, SOT23 RS-485/ RS-422 Transmitters |
| 文件： | 总11页 (文件大小：286K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2770; Rev 3; 3/11
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
General Description
Features
The MAX3293/MAX3294/MAX3295 low-power, high-
speed transmitters for RS-485/RS-422 communication
operate from a single +3.3V power supply. These
devices contain one differential transmitter. The
MAX3295 transmitter operates at data rates up to
20Mbps, with an output skew of less than 5ns, and a
guaranteed driver propagation delay below 25ns. The
MAX3293 (250kbps) and MAX3294 (2.5Mbps) are
slew-rate limited to minimize EMI and reduce reflections
caused by improperly terminated cables.
♦ Space-Saving 6-Pin SOT23 Package
♦ 250kbps/2.5Mbps/20Mbps Data Rates Available
♦ Operate from a Single +3.3V Supply
♦ ESD Protection
9kV—Human Body Model
♦ Slew-Rate Limited for Errorless Data
Transmission (MAX3293/MAX3294)
♦ 1µA Low-Current Shutdown Mode
♦ -7V to +12V Common-Mode Input Voltage Range
The MAX3293/MAX3294/MAX3295 output level is guar-
anteed at +1.5V with a standard 54Ω load, compliant
with RS-485 specifications. The transmitter draws 5mA
of supply current when unloaded, and 1µA in low-
power shutdown mode (DE = GND).
♦ Current Limiting and Thermal Shutdown for
Driver-Overload Protection
♦ Hot-Swap Inputs for Telecom Applications
♦ Automotive Temperature Range (-40°C to +125°C)
Hot-swap circuitry eliminates false transitions on the data
cable during circuit initialization or connection to a live
backplane, and short-circuit current limiting and thermal-
shutdown circuitry protect the driver against excessive
power dissipation.
Ordering Information
PART
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
6 SOT23-6
MAX3293AUT+T
MAX3294AUT+T
MAX3295AUT+T
The MAX3293/MAX3294/MAX3295 are offered in a
6-pin SOT23 package, and are specified over the
automotive temperature range.
6 SOT23-6
6 SOT23-6
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Applications
RS-485/RS-422 Communications
Selector Guide
Clock Distribution
Telecom Equipment
Automotive
MAXIMUM
DATA RATE
(Mbps)
SLEW-
RATE
LIMITED
TOP
MARK
PART
Security Equipment
Point-of-Sale Equipment
Industrial Control
ABNI or
ABVH
MAX3293AUT+T
MAX3294AUT+T
MAX3295AUT+T
0.25
2.5
20
Yes
Yes
No
ABNJ or
ABVI
ABNK or
ABVJ
Typical Operating Circuit
120Ω
Z
DI
RO
D
R
Y
Pin Configuration appears at end of data sheet.
DE
MAX3293
MAX3294
MAX3295
MAX3280E
MAX3281E
MAX3283E
MAX3284E
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
Operating Temperature Ranges
Supply Voltage (V ).............................................................+6V
DE, DI .......................................................................-0.3V to +6V
Y, Z .........................................................................-7V to +12.5V
MAX32_ _AUT...............................................-40°C to +125°C
Storage Temperature Range.............................-65°C to +160°C
Junction Temperature .....................................................+160°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
CC
Maximum Continuous Power Dissipation (T = +70°C)
A
SOT23 (derate 8.2mW/°C above +70°C).................654.1mW
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V 5ꢀ, T = T
A
to T
, unless otherwise noted. Typical values are at V
= +3.3V and T = +25°C.) (Notes 1, 2)
CC A
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
POWER SUPPLY
Supply Voltage
V
3.135
3.300
3.465
5
V
CC
Supply Current in Normal
Operation
I
No load, DI = V
or GND, DE = V
CC
mA
µA
Q
CC
Supply Current in Shutdown Mode
I
No load, DE = GND
1
10
SHDN
DRIVER
R = 50Ω (RS-422),
≤ +85°C
2.0
1.5
V
V
CC
CC
T
A
Figure 1, DE = V
,
CC
Differential Driver Output
V
V
OD
DI = GND or V
CC
R = 27Ω (RS-485),
≤ +85°C
T
A
Change in Magnitude of
Differential Output Voltage
Figure 1, R = 27Ω or 50Ω,
DE = V (Note 3)
4/MAX3295
ΔV
0.2
+3
0.2
V
V
V
OD
CC
Driver Common-Mode Output
Voltage
Figure 1, R = 27Ω or 50Ω,
DE = V , DI = V or GND
V
-1
OC
CC
CC
Change in Magnitude of Common-
Mode Voltage
ΔV
Figure 1, R = 27Ω or 50Ω (Note 3)
OC
DRIVER LOGIC
Input High Voltage
Input Low Voltage
Input Current
V
DE, DI
DE, DI
DE, DI
2.0
V
V
IH
V
0.8
+2
IL
I
-2
µA
IN
Y, Z
DE = GND,
V
V
= +12V
= -7V
-20
+20
+20
IN
IN
Output Leakage
I
µA
O
V
= GND or
CC
-20
+3.3V
(V - 1V) ≤ V
≤ +12V, output high
+25
Driver Short-Circuit Foldback
Output Current
CC
OUT
I
mA
mA
OSFD
-7V ≤ V
≤ 1V, output high
-25
OUT
0 ≤ V
≤ +12V, output low
OUT
-250
Driver Short-Circuit
Output Current
I
OSD
-7V ≤ V
≤ V , output high
+250
OUT
CC
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
ESD Protection
T
160
40
9
°C
°C
kV
TS
T
TSH
Y, Z
Human Body Model
2
_______________________________________________________________________________________
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
SWITCHING CHARACTERISTICS (MAX3293)
(V
CC
= +3.3V 5ꢀ, T = +25°C, unless otherwise noted. Typical values are at V
= +3.3V.)
A
CC
PARAMETER
SYMBOL
CONDITIONS
MIN
400
400
400
400
TYP
MAX
1300
1300
1200
1200
UNITS
t
t
PLH
PHL
Figures 2, 3; R
C = 50pF
L
= 54ꢀ,
DIFF
DIFF
DIFF
Driver Propagation Delay
ns
t
R
Driver Differential Output Rise
or Fall Time
Figures 2, 3; R
C = 50pF
L
= 54ꢀ,
ns
ns
t
F
Figures 2, 3; R
= 54ꢀ, C = 50pF,
L
Driver-Output Skew
t
-400
+400
+100
SKEW
t
= | t
- t
| (Note 5)
SKEW
PLH PHL
Differential Driver-Output Skew
Maximum Data Rate
t
Figures 2, 3; R
Figures 2, 3; R
= 54ꢀ, C = 50pF
-100
250
ns
DSKEW
DIFF
L
= 54ꢀ, C = 50pF
kbps
DIFF
L
Figures 4, 5; S2 closed, R = 500ꢀ,
C = 100pF
L
L
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
t
2000
2000
1000
1000
900
ns
ns
ns
ns
ns
ZH
Figures 4, 5; S1 closed, R = 500ꢀ,
L
t
ZL
LZ
HZ
C = 100pF
L
Figures 4, 5; S1 closed, R = 500ꢀ,
L
t
C = 100pF
L
Figures 4, 5; S2 closed, R = 500ꢀ,
L
t
C = 100pF
L
Device-to-Device Propagation
Delay Matching
Same power supply, maximum temperature
difference between devices = +30°C (Note 5)
SWITCHING CHARACTERISTICS (MAX3294)
(V
CC
= +3.3V 5ꢀ, T = +25°C, unless otherwise noted. Typical values are at V
= +3.3V.)
A
CC
PARAMETER
SYMBOL
CONDITIONS
MIN
24
TYP
MAX
70
UNITS
t
t
PLH
PHL
Figures 2, 3; R
C = 50pF
L
= 54ꢀ,
DIFF
DIFF
DIFF
Driver Propagation Delay
ns
24
70
t
R
10
70
Driver Differential Output Rise
or Fall Time
Figures 2, 3; R
C = 50pF
L
= 54ꢀ,
ns
ns
t
F
10
70
Figures 2, 3; R
= 54ꢀ, C = 50pF,
L
Driver-Output Skew
t
-40
+40
+6
SKEW
t
= | t
- t
| (Note 5)
SKEW
PLH PHL
Differential Driver-Output Skew
Maximum Data Rate
t
Figures 2, 3; R
Figures 2, 3; R
= 54ꢀ, C = 50pF
-6
ns
DSKEW
DIFF
L
= 54ꢀ, C = 50pF
2.5
Mbps
DIFF
L
Figures 4, 5; S2 closed, R = 500ꢀ,
C = 100pF
L
L
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
t
400
400
100
100
46
ns
ns
ns
ns
ns
ZH
Figures 4, 5; S1 closed, R = 500ꢀ,
L
t
ZL
LZ
HZ
C = 100pF
L
Figures 4, 5; S1 closed, R = 500ꢀ,
L
t
C = 100pF
L
Figures 4, 5; S2 closed, R = 500ꢀ,
L
t
C = 100pF
L
Device-to-Device Propagation
Delay Matching
Same power supply, maximum temperature
difference between devices = +30°C (Note 5)
_______________________________________________________________________________________
3
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
SWITCHING CHARACTERISTICS (MAX3295)
(V
CC
= +3.3V 5ꢀ, T = +25°C, unless otherwise noted. Typical values are at V
= +3.3V.)
A
CC
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
25
UNITS
t
t
PLH
PHL
Driver Propagation Delay
Figures 2, 3; R
Figures 2, 3;
= 54ꢁ, C = 50pF
ns
DIFF
L
25
T
A
T
A
T
A
T
A
= -40°C to +125°C
< +85°C
18.5
15
t
R
Driver Differential Output Rise
or Fall Time
R
DIFF
= 54ꢁ,
ns
= -40°C to +125°C
< +85°C
18.5
15
C = 50pF
L
t
F
Figures 2, 3; R
= 54ꢁ, C = 50pF,
L
|
DIFF
- t
Driver-Output Skew
t
5
5
ns
ns
SKEW
t
= | t
SKEW
PLH PHL
Differential Driver-Output Skew
t
Figures 2, 3; R
= 54ꢁ, C = 50pF
L
DSKEW
DIFF
DIFF
Figures 2, 3; R
= 54ꢁ, C = 50pF,
L
20
16
T
A
ꢀ +85°C
Maximum Data Rate
Mbps
Figures 2, 3; R
= 54ꢁ, C = 50pF
L
DIFF
Figures 4, 5; S2 closed, R = 500ꢁ,
C = 100pF
L
L
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
t
400
400
100
100
25
ns
ns
ns
ns
ns
ZH
Figures 4, 5; S1 closed, R = 500ꢁ,
L
t
ZL
LZ
HZ
C = 100pF
L
Figures 4, 5; S1 closed, R = 500ꢁ,
L
t
C = 100pF
L
Figures 4, 5; S2 closed, R = 500ꢁ,
L
t
C = 100pF
L
4/MAX3295
Device-to-Device Propagation
Delay Matching
Same power supply, maximum temperature
difference between devices = +30°C (Note 5)
Note 1: Devices production tested at +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device
ground, unless otherwise noted.
Note 3: ΔV
and ΔV
are the changes in V
and V , respectively, when the DI input changes state.
OD
OC
OD OC
Note 4: The maximum current applies to peak current just prior to foldback current limiting.
Note 5: Guaranteed by design; not production tested.
4
_______________________________________________________________________________________
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
Test Circuits and Timing Diagrams
Y
R
R
V
CC
S1
S2
R
L
OUTPUT
UNDER TEST
V
OD
C
L
V
OC
Z
Figure 1. Driver DC Test Load
Figure 4. Enable/Disable Timing Test Load
3V
DE
1.5V
1.5V
3V
DE
0V
t
t
, t
LZ
ZL(SHDN) ZL
C
C
L
Y
Y, Z
DI
R
DIFF
V
+ 0.25V
- 0.25V
OL
V
ID
2.3V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
V
OL
Z
L
Y, Z
0V
2.3V
t
V
OH
t
, t
HZ
ZH(SHDN) ZH
Figure 2. Driver Timing Test Circuit
Figure 5. Driver Enable and Disable Times
f = 1MHz, t ≤ 3ns, t ≤ 3ns
R
F
3V
0V
DI
1.5V
1.5V
t
t
PHL
PLH
1/2 V
O
Z
V
O
Y
1/2 V
O
V
= V (Y) - V (Z)
DIFF
V
0V
O
90%
90%
V
DIFF
10%
10%
-V
O
t
t
R
F
|
t
= | t - t
PLH PHL
SKEW
Figure 3. Driver Propagation Delays
_______________________________________________________________________________________
5
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
Typical Operating Characteristics
(V
CC
= +3.3V, T = +25°C, unless otherwise noted.)
A
SHUTDOWN SUPPLY CURRENT
MAX3295
SUPPLY CURRENT vs. DATA RATE
SUPPLY CURRENT vs. TEMPERATURE
vs. TEMPERATURE
2.0
1.5
2.0
1.6
1.2
0.8
0.4
0
25
DE = V
NO LOAD
DE = V
NO LOAD
NO SWITCHING
DE = GND
CC
CC
T = +85°C
20
15
10
5
A
T = +125°C
A
1.0
0.5
0
T = +25°C
A
T = -40°C
A
0
-40
-10
20
50
80
110
-40
-10
20
50
80
110
0
5
10
DATA RATE (Mbps)
15
20
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
DRIVER-OUTPUT CURRENT
vs. DRIVER-OUTPUT LOW VOLTAGE
140
120
100
80
50
40
30
20
10
0
3.5
3.0
2.5
2.0
1.5
1.0
R
R
= 100Ω
= 54Ω
DIFF
4/MAX3295
60
DIFF
40
20
0
0
2
4
6
8
10
12
1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50
DIFFERENTIAL OUTPUT VOLTAGE (V)
-40
-10
20
50
80
110
OUTPUT LOW VOLTAGE (V)
TEMPERATURE (°C)
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
DRIVER-OUTPUT CURRENT
vs. DRIVER-OUTPUT HIGH VOLTAGE
OUTPUT SKEW vs. TEMPERATURE
20
0
40
30
4
3
R
= 54Ω
DIFF
C = 50pF
L
-20
-40
-60
-80
-100
-120
t
t
PHL
20
10
0
2
1
0
PLH
-7
-5
-3
-1
1
3
5
-40
-10
20
50
80
110
-40
-10
20
50
80
110
OUTPUT HIGH VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
Typical Operating Characteristics (continued)
(V
CC
= +3.3V, T = +25°C, unless otherwise noted.)
A
UNLOADED DRIVER-OUTPUT
WAVEFORM (f = 16Mbps)
ENABLE RESPONSE TIME
DRIVER PROPAGATION DELAY
IN
MAX3293-95 toc11
MAX3293-95 toc10
MAX3293-95 toc12
DE
0V
DI
0V
Y-Z
0V
Y, Z
0V
Y, Z
0V
40ns/div
20ns/div
20ns/div
Y, Z: 1V/div
DI: 2V/div
Y, Z: 1V/div
Y, Z, DE: 2V/div
LOADED DRIVER-OUTPUT WAVEFORM
EYE DIAGRAM (f = 20Mbps)
(f = 16Mbps)
IN
IN
MAX3293-95 toc14
MAX3293-95 toc13
Y, Z
0V
Y, Z
0V
10ns/div
20ns/div
Y, Z: 500mV/div
Y, Z: 500mV/div
Pin Description
PIN
NAME
FUNCTION
Driver Input. A logic low on DI forces the noninverting output (Y) low and the inverting output (Z)
high. A logic high on DI forces the noninverting output (Y) high and the inverting output (Z) low.
1
2
3
DI
V
Positive Supply. V
= +3.3V 5ꢀ. Bypass V
to GND with a 0.1µF capacitor.
CC
CC
CC
Driver Output Enable. Force DE high to enable driver. Pull DE low to disable the driver. Hot-swap
input, see the Hot-Swap Capability section.
DE
4
5
6
Z
GND
Y
Inverting RS-485/RS-422 Output
Ground
Noninverting RS-485/RS-422 Output
_______________________________________________________________________________________
7
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
cause coupling of V
or GND to DE. These factors
CC
Detailed Description
could improperly enable the driver.
The MAX3293/MAX3294/MAX3295 are low-power
transmitters for RS-485/RS-422 communication. The
MAX3295 operates at data rates up to 20Mbps, the
MAX3294 up to 2.5Mbps (slew-rate limited), and the
MAX3293 up to 250kbps (slew-rate limited). These
devices are enabled using an active-high driver enable
(DE) input. When disabled, outputs enter a high-imped-
ance state, and the supply current reduces to 1µA.
The MAX3293/MAX3294/MAX3295 eliminate all above
issues with hot-swap circuitry. When V
rises, an
CC
internal pulldown circuit holds DE low for approximately
10µs. After the initial power-up sequence, the pulldown
circuit becomes transparent, resetting the hot-swap tol-
erable input.
The MAX3293/MAX3294/MAX3295 have a hot-swap
input structure that prevents disturbance on the differ-
ential signal lines when a circuit board is plugged into
a “hot” backplane (see the Hot-Swap Capability sec-
tion). Drivers are also short-circuit current limited and
are protected against excessive power dissipation by
thermal-shutdown circuitry.
V
CC
10μs
TIMER
Driver
The driver accepts a single-ended, logic-level input
(DI) and translates it to a differential RS-485/RS-422
level output (Y and Z). Driving DE high enables the dri-
ver, while pulling DE low places the driver outputs
(Y and Z) into a high-impedance state (see Table 1).
TIMER
Low-Power Shutdown
Force DE low to disable the MAX3293/MAX3294/
MAX3295. In shutdown mode, the device consumes a
maximum of 10µA of supply current.
5.6kΩ
DE
EN
(HOT SWAP)
2mA
100μA
4/MAX3295
Hot-Swap Capability
M1
M2
Hot-Swap Input
When circuit boards are inserted into a “hot” or pow-
ered backplane, disturbances to the enable can lead to
data errors. Upon initial circuit board insertion, the
processor undergoes its power-up sequence. During
this period, the output drivers are high impedance and
are unable to drive the DE input of the MAX3293/
MAX3294/MAX3295 to a defined logic level. Leakage
currents up to 10µA from the high-impedance output
could cause DE to drift to an incorrect logic state.
Additionally, parasitic circuit board capacitance could
Figure 6. Simplified Structure of the Driver Enable Input (DE)
DIFFERENTIAL POWER-UP GLITCH
(0.1V/μs)
2V/div
0V
V
CC
10mV/div
AC-COUPLED
Table 1. MAX3293/MAX3294/
MAX3295 (RS-485/RS-422) Transmitting
Function Table
Y
Z
10mV/div
AC-COUPLED
INPUTS
OUTPUTS
DE
0
DI
X
Y
Z
20mV/div
Y-Z
Shutdown
Shutdown
1
1
0
1
0
1
1
0
4μs/div
X = Don’t care.
Figure 7. Differential Power-Up Glitch (0.1V/µs)
8
_______________________________________________________________________________________
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
Hot-Swap Input Circuitry
off. When M1 turns off, DE reverts to a standard, high-
impedance CMOS input. Whenever V
1V, the hot-swap input is reset.
The MAX3293/MAX3294/MAX3295 enable input fea-
tures hot-swap capability. At the input, there are two
drops below
CC
NMOS devices, M1 and M2 (Figure 6). When V
CC
Hot-Swap Line Transient
During a hot-swap event when the driver is connected to
the line and is powered up, the driver must not cause the
differential signal to drop below 200mV. Figures 7, 8, and
9 show the results of the MAX3295 during power-up for
ramps from zero, an internal 10µs timer turns on M2
and sets the SR latch, which also turns on M1.
Transistors M2, a 2mA current sink, and M1, a 100µA
current sink, pull DE to GND through a 5.6kΩ resistor.
M2 is designed to pull DE to the disabled state against
an external parasitic capacitance up to 100pF that may
drive DE high. After 10µs, the timer deactivates M2
while M1 remains on, holding DE low against three-
state leakages that can drive DE high. M1 remains on
until an external source overcomes the required input
current. At this time, the SR latch resets and M1 turns
three different V
ramp rates (0.1V/µs, 1V/µs, and
CC
10V/µs). The photos show the V
ramp, the single-
CC
ended signal on each side of the 100Ω termination, as
well as the differential signal across the termination.
ESD Protection
Human Body Model
Figure 10 shows the Human Body Model, and Figure 11
shows the current waveform it generates when dis-
charged into low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a
1.5kΩ resistor.
DIFFERENTIAL POWER-UP GLITCH
(1V/μs)
2V/div
0V
V
CC
100mV/div
AC-COUPLED
Y
Z
R
C
R
D
1MΩ
1.5kΩ
100mV/div
AC-COUPLED
DISCHARGE
RESISTANCE
CHARGE-CURRENT-
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
200mV/div
Y-Z
C
100pF
STORAGE
CAPACITOR
s
SOURCE
1μs/div
Figure 8. Differential Power-Up Glitch (1V/µs)
Figure 10. Human Body ESD Test
DIFFERENTIAL POWER-UP GLITCH
(10V/μs)
2V/div
0V
V
CC
I
r
I
100%
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
P
50mV/div
AMPERES
AC-COUPLED
Y
Z
36.8%
50mV/div
AC-COUPLED
10%
0V
0V
TIME
Y-Z
100mV/div
t
RL
t
DL
CURRENT WAVEFORM
200ns/div
Figure 9. Differential Power-Up Glitch (10V/µs)
Figure 11. Current Waveform
_______________________________________________________________________________________
9
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
Reduced EMI and Reflections
Driver-Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus contention.
The first, a foldback current limit on the output stage,
provides immediate protection against short circuits over
the whole common-mode voltage range (see the Typical
Operating Characteristics). The second, a thermal-shut-
down circuit, forces the driver outputs into a high-imped-
ance state if the die temperature exceeds +160°C.
(MAX3293/MAX3294)
The MAX3293/MAX3294 are slew-rate limited, minimiz-
ing EMI and reducing reflections caused by improperly
terminated cables. Figure 12 shows Fourier analysis of
the MAX3295 transmitting a 125kHz signal. High-fre-
quency harmonics with large amplitudes are evident.
Figure 13 shows the same information, but for the slew-
rate-limited MAX3293, transmitting the same signal.
The high-frequency harmonics have much lower ampli-
tudes, and the potential for EMI is significantly reduced.
To minimize reflections, the line should be terminated at
both ends in its characteristic impedance, and stub
lengths off the main line should be kept as short as
possible. The slew-rate-limited MAX3293 and MAX3294
are more tolerant of imperfect termination.
Chip Information
PROCESS: BiCMOS
DRIVER-OUTPUT WAVEFORM AND
FFT PLOT OF MAX3295
DRIVER-OUTPUT WAVEFORM AND
FFT PLOT OF MAX3293
4/MAX3295
10dB/div
10dB/div
Figure 12. Driver-Output Waveform and FFT Plot of MAX3295
Transmitting a 125kHz Signal
Figure 13. Driver-Output Waveform and FFT Plot of MAX3293
Transmitting a 125kHz Signal
Pin Configuration
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
TOP VIEW
+
DI
1
2
3
6
5
4
Y
MAX3293
MAX3294
MAX3295
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
V
GND
Z
CC
PATTERN NO.
6 SOT23
U6CN+2
21-0058
90-0175
DE
SOT23-6
10 ______________________________________________________________________________________
20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
4/MAX3295
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
3
3/11
Added lead-free parts to the Ordering Information and Selector Guide tables
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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