1066.PDF
(
122 KB
)
Pobierz
19-0312; Rev 0; 9/94
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
_______________General Description
The MAX3212 uses Maxim’s new proprietary Auto-
Shutdown mode to reduce supply current to 1µA. The
MAX3212, with 3 RS-232 drivers and 5 RS-232 receivers,
is intended for 2.7V to 3.6V-powered EIA/TIA-232E and
V.28/V.24 serial interface. True RS-232 levels are main-
tained across the operating range. A guaranteed data
rate of 235kbps provides compatibility with popular soft-
ware for communicating with personal computers.
Supply current is reduced to 1µA with Maxim’s new
AutoShutdown feature. When the MAX3212 does not
sense a valid signal level on the receiver inputs, the on-
board power supply and drivers shut down. This occurs
if the RS-232 cable is disconnected or if the transmit-
ters of the connected peripheral are turned off. The sys-
tem turns on again when a valid level is applied to any
RS-232 receiver input. As a result, the system saves
power without changes to the existing software.
A second power-management feature is incorporated to
permit automatic shutdown when the RS-232 connection
is valid but inactive. In this case, a transition detector
facilitates shutdown when the receivers are presented
with stationary RS-232 levels for long periods.
Three-state drivers are provided on receiver outputs so
that multiple receivers, generally of different interface
standards, can be wire-ORed at the UART. The
MAX3212 is available in 28-pin SO and SSOP packages.
____________________________Features
BETTER THAN BIPOLAR!
©
1µA Supply Current Using AutoShutdown
©
Operates from Single +2.7V to +3.6V Supply
©
28-Pin SSOP or Wide SO Packages
©
Meets All EIA/TIA-232E & EIA/TIA-562 Specifications
©
Mouse Driveability–Guaranteed
©
Low-Cost, Surface-Mount External Components
©
235kbps Guaranteed Data Rate–
LapLink™ Compatible
©
+5V Logic Compatible
©
Complementary Receiver Output Always Active
©
Flow-Through Pinout
__________Typical Operating Circuit
0.68µF 1N6050
15µH
1N6050
+3.0V
0.33µF
0
.33µF
3 7
1
2 6
V
CC
V+
LN
LP
V-
26
25
5
6
FORCEON
FORCEOFF
+3.0V
TRAN
INVALID
MAX3212
13
19
T1IN
T1OUT
T1
14
T2IN
T2OUT
18
T2
15
17
T3IN
T3OUT
T3
________________________Applications
Notebook and Palmtop Computers
Peripherals
Instruments
Battery-Powered Equipment
8
R1OUT
R1IN
24
R1
5k
9
R2OUT
R2IN
23
R2
5k
10
22
R3OUT
R3IN
R3
5k
11
21
R4OUT
R4IN
R4
______________Ordering Information
5k
12
20
PART
MAX3212CWI
MAX3212CAI
TEMP. RANGE
PIN-PACKAGE
28 Wide SO
28 SSOP
R5OUT
R5IN
R5
0°C to +70°C
7
R5OUTB
R5
0°C to +70°C
5k
MAX3212EWI
MAX3212EAI
-40°C to +85°C
28 Wide SO
28 SSOP
EN
GND
-40°C to +85°C
4
28
+3.0V
AUTOSH
UTDOWN OPERATION
FORCEOFF = HIGH, FORCEON = LOW
RS-232 Present
Yes
No
Status
On
Shut Down
Pin Configuration appears at end of data sheet.
* Patent pending
________________________________________________________________ Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
ABSOLUTE MAXIMUM RATINGS
Supply Voltages
V
CC
.....................................................................-0.3V to +4.6V
V+ ............................................................(V
CC
- 0.3V) to +7.4V
V- ........................................................................-7.4V to +2.0V
LN ..............................................................-0.3V to (V+ + 1.0V)
LP.......................................................(V- - 1.0V) to (V+ + 0.3V)
Input Voltages
T_IN, EN, FORCEON, FORCEOFF .....................-0.3V to +7.0V
R_IN ..................................................................................±25V
Output Voltages
T_OUT...................
.............
...............................................±15V
R_OUT, R5OUTB, INVALID, TRAN............-0.3V to (V+ + 0.3V)
Short-Circuit Duration, T_OUT....................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
Wide SO (derate 11.76mW/°C above +70°C)...............941mW
SSOP (derate 8.00mW/°C above +70°C) .....................640mW
Operating Temperature Ranges
MAX3212C_ I .......................................................0°C to +70°C
MAX3212E_ I ....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
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
= 2.7V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS
Operating Voltage Range
Meets or exceeds EIA/TIA-232E specifications
2.7
3.6
V
All R_IN unc
onnected, FORCEON = GND
1
10
µA
µA
V
CC
Supply Current
FORCEOFF =
GND
1
10
FORCEON = FORCEOFF = V
CC
, no load
1.5
3.0
mA
LOGIC INPUT AND RECEIVER OUTPUTS
0.3V
CC
- 0.1
Input Logic Threshold Low
T_IN, EN, FORCEON, FORCEOFF
V
0.67V
CC
+ 0.1
Input Logic Threshold High
T_IN, EN, FORCEON, FORCEOFF
V
Input Current High
T_IN, EN, FORCEON,
FORCEOFF
1
µA
Input Current Low
T_IN, EN, FORCEON, FORCEOFF
T_IN, V
CC
= 3.3V
1
µA
Hysteresis
0.3
V
Logic Output Voltage Low
I
OUT
= 1.0mA
0.4
V
Logic Output Voltage High
I
OUT
= -1.0mA
V
CC
- 0.5
V
Logic Output Leakage Current
EN = GND,
0V < R_OUT < V
CC
±10
µA
AUTOSHUTDOWN
(FORCEON = GND, FORCEOFF = V
CC
)
Positive threshold
Negative threshold
3.0
Receiver Input Thresholds,
Transmitters Enabled
Receiver Input Thresholds,
Transmitters Disabled
Figure 4
V
-3.0
1µA supply current, Figure 4
-0.3
0.3
V
INVALID
Output Voltage Low
INVALID Output Voltage High
I
OUT
= 1.0mA
0.4
V
I
OUT
= -1.0mA
V
CC
- 0.6
V
Receiver Threshold to Transmitters
Enabled, t
WU
Figure 4b
250
µs
Receiver Positive or Negative
Threshold to Invalid High, t
INVH
Figure 4
1
µs
Receiver Positive or Negative
Threshold to Invalid Low, t
INVL
Figure 4
30
µs
2
_______________________________________________________________________________________
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 2.7V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
EIA/TIA-232E RECEIVERS
Input Voltage Operating Range
-25
+25
V
Input Voltage Threshold Low
0.4
V
Input Voltage Threshold High
3.0
V
Input Hysteresis
0.7
V
Input Resistance
-15V < V
IN
< 15V
3
5
7
k
½
EIA/TIA-232E TRANSMITTERS
EIA/TIA-232E TRANSMITTERS
Output Voltage Swing (V
HIGH
, V
LOW
)
All transmitters loaded with 3k
to GND
V
CC
= V- = V+ = 0V, -2V < T_OUT < 2V
½
±5.0
±5.5
V
Output Resistance
300
½
EIA/TIA-232E Short-Circuit Current
28
60
mA
MOUSE DRIVEABILITY
TIN = T2IN = GND, T3IN = V
CC
,
T3OUT loaded with 3k
Transmitter Output Voltage
to GND,
T1OUT and T2OUT loaded with 5mA
½
±5
V
TIMING CHARACTERISTICS
(V
CC
= 2.7V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R
L
= 3k
½
, C
L
= 1000pF, one transmitter
switching, 150pF load on each receiver
Data Rate
235
250
kbps
Receiver Output Enable Time
t
ER
t
DR
70
200
ns
Receiver Output Disable Time
420
700
ns
Transmitter Output Enable Time
t
ET
Includes power-supply start-up
250
µs
Transmitter Output Disable Time
t
DT
t
PHLR
600
ns
630
2000
Receiver Propagation Delay
150pF load
ns
t
PLHR
630
2000
Receiver Skew
ï
t
PHL -
t
PLH
ï
40
ns
t
PHLT
t
PLHT
800
2000
Transmitter Propagation Delay
2500pF
ïï
3k
½
load
ns
800
2000
t
PHL -
t
PLH
Transmitter Skew
ï
ï
52
ns
R
L
= 3k
,
measured from +3V
to -3V or -3V to +3V
½
to 7k
½
C
L
= 50pF to 2500pF
4.0
10
30
Transition-Region Slew Rate
V/µs
C
L
= 50pF to 1000pF
6
13
30
EN High to TRAN
Reset Delay
5
µs
EN High Pulse Width
1
µs
_______________________________________________________________________________________
3
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
__________________________________________Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
TRANSMITTING SUPPLY CURRENT
vs. DATA RATE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TRANSMITTING SUPPLY CURRENT
vs. LOAD CAPACITANCE
65
45
60
60
50
3k
W
+ 235kbps
40
55
40
50
235kbps
35
45
30
30
40
20
35
120kbps
25
30
3k
W
+ 120kbps
3k
10
TRANSMITTERS LOADED
WITH 3k
W
+ 2500pF
1 TRANSMITTER (FULL DATA RATE)
2 TRANSMITTERS (DATA RATE/8)
25
W
+ 20kbps
3k
W
ONLY
20
0
20
20kbps
-10
15
15
0
50
100
150
200
250
0
1000
2000
3000
4000
5000
2.0
2.5
3.0
3.5
4.0
DATA RATE (kbps)
SUPPLY VOLTAGE (V)
LOAD CAPACITANCE/TRANSMITTER (pF)
SLEW RATE
vs. LOAD CAPACITANCE
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE AT 235kbps
14
7.5
V
OUT
+
12
5.0
+SLEW
10
TRANSMITTERS LOADED WITH 3k
W
AND SPECIFIED CAPACITANCE
-SLEW
2.5
8
0
6
-2.5
4
TRANSMITTERS LOADED
WITH 3k
W
AND SPECIFIED
CAPACITANCE AT 232kbps
V
OUT
-
-5.0
2
0
-7.5
0
1000
2000
3000
4000
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE/TRANSMITTER (pF)
LOAD CAPACITANCE/TRANSMITTER (pF)
TIME TO EXIT SHUTDOWN: ONE
TRANSMITTER HIGH, ONE TRANSMITTER LOW
FORCEON,
FORCEOFF
V
OH
0V
T_OUT
0V
V
OL
R
L
= 3k
W
||
2500pF
100
m
s/div
4
_______________________________________________________________________________________
+2.7V to +3.6V-Powered, 1µA Supply Current,
3-Driver/5-Receiver, True RS-232 Transceiver
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1
LN
Inductor/Diode Connection Point
2
LP
Inductor/Diode Connection Point
3
V
CC
Supply Voltage Input, 2.7V to 3.6V
Receiver Enable Control. Drive EN low to force receiver outputs into a high-Z state. Drive
EN high for normal operation. Cycle EN high then low to reset TRAN. TRAN is always low
when EN is high.
4
EN
Transition Detection Output. TRAN latches high when a transition occurs on any receiver
input while EN is low. Reset by cycling the EN pin high then low.
5
TRAN
Output of Invalid Signal Detector. Low if invalid RS-232 levels are present on all
receiver inputs, otherwise high.
6
INVALID
7
R5OUTB
Complementary Output of R5OUT—always active
8–12
R1OUT–R5OUT
Receiver Outputs. Swing from GND to V
CC
. High-impedance when EN is low.
13, 14, 15
T1IN, T2IN, T3IN
Transmitter Inputs
16
V-
Negative Supply generated on-board
17, 18, 19
T3OUT, T2OUT, T1OUT
Transmitter Outputs
20–24
R5IN–R1IN
Receiver Inputs
Drive low to shut down transmitters and on-board power supply, overriding all automatic
circuitry and FORCEON (see Figure 3).
25
FORCEOFF
Drive high to
overide automatic circuitry, keeping transmitters on (see Figure 3).
FORCEOFF = high.
26
FORCEON
27
V+
Positive Supply generated on-board
28
GND
Ground
_______________Detailed Description
The MAX3212 line driver/receiver is intended for 3V-
powered EIA/TIA-232E and V.28/V.24 communications
interfaces where 3 drivers and 5 receivers are required.
The operating voltage range extends from 3.6V down to
2.7V while still maintaining true RS-232 and EIA/TIA-562
transmitter output voltage levels.
The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply section
converts the supplied 3V to about ±6.5V, to provide
the voltages necessary for the drivers to meet true RS-
232 levels. External components are small and inex-
pensive.
The transmitters and receivers are guaranteed to oper-
ate at data rates of 235kbps.
The MAX3212 is equipped with Maxim’s new propri-
etary AutoShutdown circuitry. This achieves a supply
current of 1µA by shutting down the device when the
RS-232 cable is disconnected or when the connected
peripheral transmitters are turned off. While shut down,
all receivers can remain active or can be disabled
under logic control. A complementary receiver remains
active in all cases, enabling a system incorporating the
MAX3212 to remain shut down and still monitor incom-
ing RS-232 activity.
Three-state drivers on all receiver outputs are provided
so that multiple receivers, generally of different inter-
face standards, can be wire-ORed at the UART.
Switch-Mode Power Supply
The switch-mode power supply uses a single inductor
with two inexpensive diodes and two capacitors to
generate ±6.5V from the 2.7V to 3.6V input. The Typical
Operating Circuitshows the complete circuit for the pow-
er supply.
Use a 15
H inductor with a saturation current rating of at
least 350mA and under 1
m
resistance. Use 1N6050
diodes or equivalent. Surface-mount equivalents for the
1N6050 include the Motorola MMBD6050LT1, Philips
PMBD6050, and Allegro (formerly Sprague) TMPD6050LT.
For C1 and C2, use ceramic capacitors with values no
less than indicated in the Typical Operating Circuit.
These capacitors determine the ripple on V+ and V-, but
W
_______________________________________________________________________________________
5
Plik z chomika:
Kot_Maciek
Inne pliki z tego folderu:
0001.PDF
(10 KB)
1003.PDF
(374 KB)
1002.PDF
(139 KB)
1004.PDF
(342 KB)
1005.PDF
(170 KB)
Inne foldery tego chomika:
PDF2
PDF3
SPICE
Zgłoś jeśli
naruszono regulamin