MAX3218C/D [MAXIM]
1レA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown⑩; 1レ供电电流， 1.8V至4.25V供电的RS - 232收发器，带有AutoShutdown⑩
| 型号： | MAX3218C/D |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1レA Supply Current, 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown⑩ |
| 文件： | 总12页 (文件大小：125K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0380; Rev 0; 3/95
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218*
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
BETTER THAN BIPOLAR!
The MAX3218 RS-232 transceiver is intended for bat-
tery-powered EIA/TIA-232E and V.28/V.24 communica-
tions interfaces that need two drivers and two receivers
with minimum power consumption from a single low-
voltage supply. It provides a wide +1.8V to +4.25V
operating voltage range while maintaining true RS-232
and EIA/TIA-562 voltage levels. The MAX3218 runs
from two alkaline, NiCd, or NiMH cells without any form
of voltage regulator. A guaranteed 120kbps data rate
provides compatibility with popular software for com-
municating with personal computers.
♦ 1µA Supply Current Using AutoShutdown™
♦ Operates Directly from Two Alkaline,
NiCd or NiMH Cells
♦ +1.8V to +4.25V Single-Supply Voltage Range
♦ 120kbps Data Rate Guaranteed
♦ Low-Cost Surface-Mount Components
♦ Meets EIA/TIA-232E Specifications
♦ Three-State Receiver Outputs
♦ Flow-Through Pinout
Supply current is reduced to 1µA with Maxim’s new
AutoShutdown™ feature. When the MAX3218 does not
sense a valid signal level on the receiver inputs, the on-
b oa rd p owe r-s up p ly a nd d rive rs s hut d own. This
occurs if the RS-232 cable is disconnected or if the
transmitters of the connected peripheral are turned off.
The system turns on again when a valid level is applied
to either RS-232 receiver input. As a result, the system
saves power without changes to the existing software.
Additionally, the MAX3218 can be forced into or out of
shutdown, under logic control.
♦ On-Board DC-DC Converters
♦ 20-Pin SSOP and DIP Packages
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 Plastic DIP
20 SSOP
MAX3218CPP
MAX3218CAP
MAX3218C/D
MAX3218EPP
MAX3218EAP
While shut down, all receivers can remain active or can
be disabled under logic control, permitting a system
incorporating the CMOS MAX3218 to monitor external
devices while in low-power shutdown. Three-state dri-
vers are provided on both receiver outputs so that multi-
ple receivers, generally of different interface standards,
can be on the same bus. The MAX3218 is available in
20-pin DIP and SSOP packages.
Dice†
20 Plastic DIP
20 SSOP
† Contact factory for dice specifications.
__________________P in Co n fig u ra t io n
________________________Ap p lic a t io n s
Battery-Powered Equipment
Subnotebook Computers
PDAs
TOP VIEW
LX
GND
V+
1
2
20
19
18
17
16
15
14
13
12
11
INVALID
Hand-Held Equipment
Peripherals
C1+
FORCEON
FORCEOFF
3
GND
C1-
4
Cellular Phones
MAX3218
GND
5
V
CC
V-
6
T1IN
T2IN
T1OUT
T2OUT
R1IN
R2IN
7
8
R1OUT
R2OUT
9
10
* Patent Pending
™ AutoShutdown is a trademark of Maxim Integrated Products.
DIP/SSOP
________________________________________________________________ Maxim Integrated Products
1
Ca ll t o ll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 fo r fre e s a m p le s o r lit e ra t u re .
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
ABSOLUTE MAXIMUM RATINGS
Supply Voltages
Short-Circuit Duration, R_OUT, T_OUT to GND ....... Continuous
V
CC
....................................................................-0.3V to +4.6V
Continuous Power Dissipation (T = +70°C)
A
V+ .......................................................... (V - 0.3V) to +7.5V
V- .......................................................................+0.3V to -7.4V
Plastic DIP (derate 11.11mW/°C above +70°C) ..........889mW
SSOP (derate 8.00mW/°C above +70°C) ..................640mW
Operating Temperature Ranges
CC
V
CC
to V-..........................................................................+12V
LX ................................................................-0.3V to (1V + V+)
Input Voltages
T_IN, FORCEON, FORCEOFF ............................ -0.3V to +7V
R_IN .................................................................................±25V
Output Voltages
MAX3218C_ P ................................................... 0°C to +70°C
MAX3218E_ P ................................................. -40°C to +85°C
Storage Temperature Range ........................... -65°C to +150°C
Lead Temperature (soldering, 10sec) ........................... +300°C
MAX3218
T_OUT.............................................................................±15V)
R_OUT....................................................-0.3V to (V + 0.3V)
CC
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
(Circuit of Figure 1, V = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T = T
to T
, unless otherwise noted.
CC
A
MIN
MAX
Typical values are at V = 3.0V, T = +25°C.)
CC
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS
Operating Voltage Range
1.8
4.25
10
V
V
= 3.0V, T = +25°C, all R_IN open,
A
CC
Supply Current, AutoShutdown™
1.0
1.0
2.0
µA
µA
mA
FORCEON = GND, FORCEOFF = V
CC
Supply Current, Shutdown
FORCEOFF = GND, T = +25°C, V = 3.0V
10
CC
A
Supply Current,
AutoShutdown™ Disabled
FORCEON = FORCEOFF = V = 3.0V, no load
3.0
CC
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
Input Logic Threshold High
Input Leakage Current
Output Voltage Low
T_IN, FORCEON, FORCEOFF
T_IN, FORCEON, FORCEOFF
T_IN, FORCEON = FORCEOFF = 0V or V
0.33 x V
V
V
CC
0.67 x V
CC
0.001
±1
µA
V
CC
R_OUT, I
= 1.0mA
= -0.4mA
0.4
OUT
OUT
Output Voltage High
R_OUT, I
V
- 0.25
V
- 0.08
V
CC
CC
R_OUT, 0V ≤ R_OUT ≤ V
FORCEON = FORCEOFF = 0V
,
CC
Output Leakage Current
0.05
±10
2.8
µA
AUTOSHUTDOWN (FORCEON = GND, FORCEOFF = V
)
CC
Positive threshold
Negative threshold
Receiver Input Thresholds,
Figure 4a
V
V
Transmitters Enabled
-2.8
-0.3
Receiver Input Thresholds
Transmitters Disabled
1µA supply current, Figure 4a
0.3
0.4
INVALID Output Low Voltage
INVALID Output High Voltage
I
= 1.0mA, -0.3V < R_IN < 0.3V
= -0.4mA, R_IN > 2.8V
V
V
OUT
V
- 0.25
I
CC
|
|
OUT
2
_______________________________________________________________________________________
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T = T
to T
, unless otherwise noted.
CC
A
MIN
MAX
Typical values are at V = 3.0V, T = +25°C.)
CC
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
EIA/TIA-232E RECEIVER INPUTS
Input Voltage Range
-25
0.4
0.3
+25
V
V
V
= 2.0V to 4.25V
CC
Input Threshold Low
Input Threshold High
V
CC
= 1.8V to 4.25V
= 1.8V to 4.25V
= 1.8V to 3.6V
V
CC
3.0
2.8
V
V
CC
Input Hysteresis
Input Resistance
0.7
5
V
-15V < R_IN < 15V
3
7
kΩ
EIA/TIA-232E TRANSMITTER OUTPUTS
Output Voltage Swing
Output Resistance
All transmitter outputs loaded with 3kΩ to ground
= 0V, -2V < T_OUT < 2V
±5
±6
V
Ω
V
CC
300
Output Short-Circuit Current
±24
±100
mA
TIMING CHARACTERISTICS
(Circuit of Figure 1, V = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, T = T
to T
, unless otherwise noted.
CC
A
MIN
MAX
Typical values are at V = 3.0V, T = +25°C.)
A
CC
PARAMETER
Data Rate
SYMBOL
CONDITIONS
MIN
120
TYP
MAX
UNITS
2500pF || 3kΩ load each transmitter, one trans-
mitter switching, 150pF load each receiver
235
kbps
Receiver Output Enable Time
Receiver Output Disable Time
Transmitter Output Enable Time
Transmitter Output Disable Time
t
90
300
500
450
ns
ns
µs
ns
ER
t
200
250
500
290
260
1.9
DR
t
ET
t
DT
t
t
150pF load
1000
1000
2.7
PHLR
PLHR
Receiver Propagation Delay
Transmitter Propagation Delay
ns
µs
150pF load
t
2500pF || 3kΩ load
2500pF || 3kΩ load
PHLT
PLHT
t
1.8
2.7
T
A
= +25°C, V = 3.0V, R = 3kΩ to 7kΩ,
L
CC
Transition Region Slew Rate
C
= 50pF to 2500pF, measured from
3.0
30
V/µs
L
+3V to -3V or -3V to +3V
AUTOSHUTDOWN TIMING
Receiver Threshold to
Transmitters Enabled
t
Figure 4b
Figure 4b
Figure 4b
250
1
µs
µs
µs
WU
Receiver Positive or Negative
Threshold to INVALID High
t
INVH
Receiver Positive or Negative
Threshold to INVALID Low
t
30
INVL
_______________________________________________________________________________________
3
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(Circuit of Figure 1, V = 1.8V, all transmitter outputs loaded with 3kΩ, T = +25°C, unless otherwise noted.)
CC
A
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
TRANSMITTING SUPPLY CURRENT
vs. LOAD CAPACITANCE
140
120
100
80
100
90
1 TRANSMITTER FULL DATA RATE
1 TRANSMITTER 1/8 DATA RATE
L
V
= 2.4V
CC
R = 3kΩ + 2500pF
80
70
60
235kbps
120kbps
MAX3218
TRANSMITTER 1 OPERATING
AT SPECIFIED BIT RATE,
TRANSMITTER 2 OPERATING
AT 1/16 THAT RATE.
240kbps
60
120kbps
50
40
20kbps
40
20
0kbps
20kbps
1000
30
20
0
1.8
2.4
3.0
3.6
4.2
0
2000
3000
4000 5000
SUPPLY VOLTAGE (V)
LOAD CAPACITANCE (pF)
TIME TO EXIT SHUTDOWN
(ONE TRANSMITTER HIGH,
ONE TRANSMITTER LOW)
FORCEON, FORCEOFF
V
OH
2V/div
T_OUT
V
1.8V
CC =
V
OL
R = 3kΩ || 2500pF
L
100µs/div
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CAPACITANCE AT 120kbps
SLEW RATE vs.
TRANSMITTER CAPACITANCE
8
6
12
10
8
V
OUT+
4
2
0
+SLEW
-SLEW
6
-2
-4
4
DATA RATE 120kbps,
TRANSMITTERS LOADED WITH
3kΩ PLUS INDICATED CAPACITANCE
V
OUT-
2
0
-6
-8
1000
LOAD CAPACITANCE (pF)
0
2000
3000
4000 5000
1000
LOAD CAPACITANCE (pF)
0
2000
3000
4000 5000
4
_______________________________________________________________________________________
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218
______________________________________________________________P in De s c rip t io n
PIN
NAME
FUNCTION
LX
Inductor/Diode Connection Point
1
Output of Invalid Signal Detector. Low if invalid RS-232 levels are present on all receiver inputs,
otherwise high.
2
3
4
INVALID
FORCEON
FORCEOFF
GND
Drive high when FORCEOFF = high to override automatic circuitry, keeping transmitters on.
Drive low to shut down transmitters and on-board power supply, overriding all automatic
circuitry and FORCEON.
5, 17, 20
6
Ground
V
CC
Supply Voltage Input, 1.8V to 4.25V. Bypass to GND with at least 1µF.
Transmitter Inputs
7, 8
T1IN, T2IN
R1OUT, R2OUT
R2IN, R1IN
T2OUT, T1OUT
V-
9, 10
11, 12
13, 14
15
Receiver Outputs
Receiver Inputs
Transmitter Outputs, swing between V+ and V-
Negative Supply generated on-board
Terminal for Charge-Pump Capacitor
Positive Supply generated on-board
16, 18
19
C1-, C1+
V+
The MAX3218 is equipped with Maxim’s new propri-
_______________De t a ile d De s c rip t io n
etary AutoShutdown™ circuitry. This achieves a 1µA
supply current by shutting down the device when the
RS-232 cable is disconnected or when the connected
peripheral transmitters are turned off. While shut down,
both receivers can remain active or can be disabled
under logic control. With this feature, the MAX3218 can
be in low-power shutdown mode and still monitor activi-
ty on external devices. Three-state drivers are provid-
ed on both receiver outputs.
The MAX3218 line driver/receiver is intended for bat-
tery-powered EIA/TIA-232 and V.28/V.24 communica-
tions inte rfa c e s tha t re q uire two d rive rs a nd two
receivers. The operating voltage extends from 1.8V to
4.25V, ye t the d e vic e ma inta ins true RS-232 a nd
EIA/TIA-562 transmitter output voltage levels. This wide
supply voltage range permits direct operation from a
variety of batteries without the need for a voltage regu-
lator. For example, the MAX3218 can be run directly
from a single lithium cell or a pair of alkaline cells. It
can also be run directly from two NiCd or NiMH cells
from full-charge voltage down to the normal 0.9V/cell
end-of-life point. The 4.25V maximum supply voltage
allows the two rechargeable cells to be trickle- or fast-
charged while driving the MAX3218.
Three-state drivers on both receiver outputs are provid-
ed so that multiple receivers, generally of different inter-
face standards, can be wire-ORed at the UART.
S w it c h -Mo d e P o w e r S u p p ly
The switch-mode power supply uses a single inductor
with one diode and three small capacitors to generate
±6.5V from an input voltage in the 1.8V to 4.25V range.
The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply section
converts the supplied input voltage to 6.5V, providing the
voltages necessary for the drivers to meet true RS-232
levels. External components are small and inexpensive.
Inductor Selection
Use a 15µH inductor with a saturation current rating of at
least 350mA and less than 1Ω resistance. Table 1 lists
suppliers of inductors that meet the 15µH/350mA/1Ω
specifications.
The transmitters and receivers are guaranteed to oper-
ate at 120kbps data rates, providing compatibility with
LapLink™ and other high-speed communications soft-
ware.
™ LapLink is a trademark of Traveling Software, Inc.
AutoShutdown is a trademark of Maxim Integrated Products.
_______________________________________________________________________________________
5
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
Table 1. Suggested Component Suppliers
MANUFACTURER
Inductors
PART NUMBER
PHONE
FAX
Murata-Erie
LQH4N150K-TA
USA (814) 237-1431
USA (814) 238-0490
USA (708) 956-0666
Japan (03) 3607-5111
USA (708) 956-0702
Japan (03) 3607-5428
Sumida
CD43150
MAX3218
USA (708) 803-6100
Japan (03) 3278-5111
USA (708) 803-6296
Japan (03) 3278-5358
TDK
NLC453232T-150K
Diodes—Surface-Mount
Allegro
TMPD6050LT
USA (508) 853-5000
USA (516) 435-1110
USA (408) 749-0510
USA (401) 762-3800
USA (508) 853-7556
USA (516) 435-1824
USA (408) 991-7420
USA (401) 767-4493
Central Semiconductor
Motorola
CMPSH-3 (Schottky)
MMBD6050LT1 (silicon)
PMBD6050 (silicon)
Philips
Diodes—Through-Hole
1N6050 (silicon),
1N5817 (Schottky)
USA (408) 749-0510
USA (408) 991-7420
Motorola
Diode Selection
15µH
1N6050
1.8V to
Key diode specifications are fast recovery time (<10ns),
average current rating (>100mA), and peak current rat-
ing (>350mA). Inexpensive fast silicon diodes, such as
the 1N6050, are generally recommended. More expen-
sive Schottky diodes improve efficiency and give slightly
better performance at very low VCC voltages. Table 1
lists suppliers of both surface-mount and through-hole
diodes. 1N914s are usually satisfactory, but specifica-
tions and performance vary widely with different manu-
facturers.
4.25V
C2
1µF
C4
1µF
6
1
19
V+
V
LX
CC
15
V-
C3
1µF
3
FORCEON
FORCEOFF
18
16
4
2
MAX3218
T1
C1+
C1-
C1
0.47µF
INVALID
T1IN
T1OUT 14
7
Capacitor Selection
Use capacitors with values at least as indicated in
Figure 1. Capacitor C2 determines the ripple on V+, but
not the absolute voltage. Capacitors C1 and C3 deter-
mine both the ripple and the absolute voltage of V-.
Bypass VCC to GND with at least 1µF (C4) placed close
8
9
T2IN
T2OUT 13
R1IN 12
T2
R1
R1OUT
5k
to pins 5 and 6. If the V line is not bypassed else-
CC
where (e.g., at the power supply), increase C4 to 4.7µF.
R2OUT
10
R2IN 11
R2
You may use ceramic or polarized capacitors in all
locations. If you use polarized capacitors, tantalum
types are preferred because of the high operating fre-
quency of the power supplies (about 250kHz). If alu-
minum e le c trolytic s a re us e d , hig he r c a p a c ita nc e
values may be required.
5k
GND
5, 17, 20
Figure 1. Typical Operating Circuit
6
_______________________________________________________________________________________
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218
Table 2. Receiver Status
FORCEOFF
FORCEON
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEON
FORCEOFF
RECEIVER STATUS
INVALID
X
H
L
H
X
L
Receiver Enabled
Receiver Disabled
MAX3218
S h u t d o w n
When FORCEOFF is low, power supplies are disabled
and the transmitters are placed in a high-impedance
state. Receiver operation is not affected by taking
FORCEOFF low. Power consumption is dramatically
reduced in shutdown mode. Supply current is minimized
when the receiver inputs are static in any one of three
I/O
CHIP
WITH
UART
CPU
RS-232
states: floating (ground), GND, or V
.
CC
Au t o S h u t d o w n ™
A 1µA supply current is achieved with Maxim’s new
AutoShutdown feature, which operates when FORCEON
is low and FORCEOFF is high. When the MAX3218
senses no valid signal level on either receiver input for
typically 30µs, the on-board power supply and drivers
shut down, reducing supply current to 1µA. Internal 5kΩ
resistors pull undriven receiver inputs to ground. This
occurs if the RS-232 cable is disconnected or if the con-
nected peripheral transmitters are turned off. The sys-
tem turns on again when a valid level is applied to either
RS-232 receiver input. As a result, the system saves
power without changes to the existing BIOS or operating
system. When using the AutoShutdown feature, INVALID
is high when the device is on and low when the device is
shut down. The INVALID output indicates the condition
of the receiver inputs.
Figure 2. Interface Under Control of PMU
RS -2 3 2 Drive rs
The two drivers are identical, and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when VCC is
between 1.8V and 4.25V. One transmitter can drive up
to 3kΩ in p a ra lle l with 2500p F a t up to 120kb p s .
Connect unused drivers to either GND or VCC. When
FORCEOFF is driven low, or when AutoShutdown circuit-
ry senses invalid voltage levels at all receiver inputs, the
drivers are disabled and their outputs are forced into a
high-impedance state. Driver inputs do not have internal
pull-up resistors.
Table 3 summarizes the MAX3218 operating modes.
FORCEON and FORCEOFF override the automatic cir-
cuitry and force the transceiver into its normal operating
state or into its low-power standby state. When neither
control is asserted, the IC selects between these states
automatically based on receiver input levels. Figure 4
depicts valid and invalid RS-232 receiver levels. The
RS -2 3 2 Re c e ive rs
The two re c e ive rs a re id e ntic a l, a nd a c c e p t b oth
EIA/TIA-232E a nd EIA/TIA-562 inp ut s ig na ls . The
CMOS receiver outputs are inverting and swing rail-to-
rail. Receivers are disabled only when FORCEON and
FORCEOFF inputs are low. (See Table 2.)
Table 3. AutoShutdown Logic
RS-232 SIGNAL
PRESENT AT
RECEIVER INPUT
FORCEOFF INPUT
FORCEON INPUT
INVALID OUTPUT
TRANSCEIVER STATUS
Normal Operation
Yes
No
H
H
H
L
X
H
L
H
L
L
H
L
Normal Operation (Forced On)
Shutdown (AutoShutdown)
Shutdown (Forced Off)
No
Yes
No
X
X
L
Shutdown (Forced Off)
_______________________________________________________________________________________
7
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218 shuts down after sensing invalid RS-232 levels
for greater than 30µs, ensuring that the AutoShutdown
mode is not enabled for slow-moving signals (>1V/µs).
drawn directly from the battery, without suffering the
efficiency losses of the DC-DC converter. This pro-
longs battery life.
Another system with AutoShutdown may need a period
of time to wake up. Figure 5 shows a circuit that forces
the transmitters on for 100ms after start-up, allowing
enough time for the other system to realize that the
MAX3218 system is awake. If the other system outputs
valid RS-232 signals within that time, the RS-232 ports on
both systems remain enabled.
Bypass the input supplies with 0.1µF at VCC (C4) and at
least 1µF at the inductor (C5). Increase C5 to 4.7µF if
the power supply has no other bypass capacitor con-
nected to it.
Lo w -P o w e r Op e ra t io n
The following suggestions will help you get maximum
life out of your batteries.
MAX3218
__________Ap p lic a t io n s In fo rm a t io n
Transmit at the highest practical data rate. Although
this raises the supply current while transmission is in
progress, the transmission will be over sooner. If the
MAX3218 is shut down (using FORCEOFF) as soon as
each transmission ends, this practice will save energy.
Op e ra t io n fro m Re g u la t e d /Un re g u la t e d
Du a l S ys t e m P o w e r S u p p lie s
The MAX3218 is intended for use with three different
power-supply sources: it can be powered directly from
a battery, from a 3.0V or 3.3V power supply, or simulta-
neously from both. Figure 1 shows the single-supply
configuration. Figure 6 shows the circuit for operation
from both a 3V supply and a raw battery supply—an
ideal configuration where a regulated 3V supply is
being derived from two cells. In this application, the
MAX3218’s logic levels remain appropriate for interface
with 3V logic, yet most of the power for the MAX3218 is
Operate your whole system from the raw battery volt-
age rather than suffer the losses of a regulator or DC-
DC converter. If this is not possible, but your system is
powered from two cells and employs a 3V DC-DC con-
verter to generate the main logic supply, use the circuit
of Figure 6. This circuit draws most of the MAX3218’s
power straight from the battery, but still provides logic-
level compatibility with the 3V logic.
+0.3V to +2.8V
-0.3V to -2.8V
+
-
FORCEOFF
FORCEON
POWER DOWN
+
-
R_IN
Rx
R_OUT
•
30µs
DELAY
FORCEON
FORCEOFF
INVALID
•
•
•
•
•
FORCEOFF FORCEON INVALID POWER DOWN
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
0
0
0
1
1
1
INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.
POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3. AutoShutdown Logic
_______________________________________________________________________________________
8
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218
Keep communications cables short to minimize capaci-
tive loading. Lowering the capacitive loading on the
transmitter outputs reduces the MAX3218’s power con-
sumption. Using short, low-capacitance cable also
helps transmission at the highest data rates.
TRANSMITTERS ENABLED, INVALID HIGH
EIA/TIA-2 3 2 E a n d
+2.8V
INDETERMINATE
_____________EIA/TIA-5 6 2 S t a n d a rd s
RS-232 circuits consume much of their power because
the EIA/TIA-232E standard demands that the transmit-
ters deliver at least 5V to receivers with impedances
that can be as low as 3kΩ. For applications where
+0.3V
0V
AUTOSHUTDOWN, TRANSMITTERS DISABLED,
1µA SUPPLY CURRENT, INVALID LOW
-0.3V
INDETERMINATE
power consumption is critical, the EIA/TIA-562 standard
-2.8V
provides an alternative.
TRANSMITTERS ENABLED, INVALID HIGH
EIA/TIA-562 transmitter output voltage levels need only
reach ±3.7V, and because they have to drive the same
3kΩ receiver loads, the total power consumption is con-
s id e ra b ly re d uc e d . Sinc e the EIA/TIA-232E a nd
EIA/TIA-562 receiver input voltage thresholds are the
s a me , inte rop e ra b ility b e twe e n EIA/TIA-232E a nd
EIA/TIA-562 devices is guaranteed. Maxim’s MAX560
and MAX561 are EIA/TIA-562 transceivers that operate
on a single supply from 3.0V to 3.6V, and the MAX562
(a)
RECEIVER
INPUT
VOLTAGE
(V)
transceiver operates from 2.7V to 5.25V while produc-
ing EIA/TIA-562 levels.
INVALID
REGION
V
CC
POWER
MANAGEMENT
UNIT
INVALID
OUTPUT
(V)
MASTER SHDN LINE
0.1µF
1M
0
t
t
INVH
INVL
V+
FORCEOFF FORCEON
MAX3218
V
CC
0V
V-
t
WU
(b)
Figure 4. AutoShutdown Trip Levels
Figure 5. AutoShutdown with Initial Turn-On to Wake Up a
System
_______________________________________________________________________________________
9
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
15µH
1N6050
1µF
C2
C5
1µF
3V
DC-DC
CONVERTER
1
LX
19
V+
6
MAX878
OR
V
15
18
16
CC
V-
MAX756
OR
C4
0.1µF
C3
1µF
3
FORCEON
MAX856
MAX3218
4
2
C1+
C1-
FORCEOFF
C1
0.47µF
MAX3218
T1
INVALID
T1IN
T1OUT 14
7
8
9
T2IN
T2OUT 13
R1IN 12
T2
R1
R1OUT
5k
R2OUT
10
R2IN 11
R2
5k
GND
5, 17, 20
Figure 6. Operating from Unregulated and Regulated Supplies
10 ______________________________________________________________________________________
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
MAX3218
_____+3 V-P o w e re d EIA/TIA-2 3 2 a n d EIA/TIA-5 6 2 Tra n s c e ive rs fro m Ma x im
GUAR-
No. OF
SUPPLY
VOLTAGE
(V)
No. OF
TRANSMITTERS/
RECEIVERS
ANTEED
DATA
EIA/TIA-
232
OR 562
RECEIVERS
ACTIVE IN
SHUTDOWN
PART
FEATURES
RATE
(kbps)
MAX212
3.0 to 3.6
2.7 to 3.6
3/5
3/5
5
5
120
232
232
Drives mice
AutoShutdown, complementary
receiver, drives mice, transient
detection
MAX3212
120
Operates directly from a battery
without a voltage regulator
MAX218
1.8 to 4.25
1.8 to 4.25
2/2
2/2
2
2
120
120
232
232
Same as MAX218 but with
AutoShutdown
MAX3218
MAX560
MAX561
MAX562
MAX563
MAX3222
MAX3223
MAX3232
3.0 to 3.6
3.0 to 3.6
2.7 to 5.25
3.0 to 3.6
3.0 to 5.5
3.0 to 5.5
3.0 to 5.5
4/5
4/5
3/5
2/2
2/2
2/2
2/2
2
0
5
2
2
2
2
120
120
230
120
120
120
120
562
562
562
562
232
232
232
Pin-compatible with MAX213
Pin-compatible with MAX214
Wide supply range
0.1µF capacitors
0.1µF capacitors
AutoShutdown, 0.1µF capacitors
Pin-compatible with MAX232
0.1µF capacitors, 2 complemen-
tary receivers, drives mice
MAX3241
MAX3243
3.0 to 5.5
3.0 to 5.5
3/5
3/5
5
1
120
120
232
232
0.1µF capacitors, AutoShutdown,
complementary receiver,
drives mice
______________________________________________________________________________________ 11
1 µA S u p p ly Cu rre n t , 1 .8 V t o 4 .2 5 V-P o w e re d
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n ™
___________________Ch ip To p o g ra p h y
INVALID LX GND
V+
FORCEON
C1+
FORCEOFF
GND
C1-
V-
MAX3218
0. 101"
(2. 565mm)
GND
T1OUT
T2OUT
V
CC
T1IN
T2IN
R1OUT
R1IN
R2OUT
R2IN
0. 122"
(3. 099mm)
TRANSISTOR COUNT: 571
SUBSTRATE CONNECTED TO GND
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.068
MAX
0.078
0.008
0.015
0.008
MIN
1.73
0.05
0.25
0.09
MAX
1.99
0.21
0.38
0.20
A
A1 0.002
B
C
D
E
e
0.010
0.004
SEE VARIATIONS
α
0.205
0.209
5.20
5.38
E
H
0.0256 BSC
0.65 BSC
H
L
0.301
0.311
0.037
8˚
7.65
0.63
0˚
7.90
0.95
8˚
0.025
0˚
C
α
L
INCHES
MILLIMETERS
DIM PINS
MAX
6.33
MIN MAX MIN
0.239 0.249 6.07
0.239 0.249 6.07
0.278 0.289 7.07
0.317 0.328 8.07
0.397 0.407 10.07
e
D
D
D
D
D
14
16
20
24
28
6.33
SSOP
7.33
SHRINK
A
8.33
SMALL OUTLINE
PACKAGE
10.33
21-0056A
B
A1
D
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.
12 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1995 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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