MAX3244 ,1µA Supply Current, 3.0V to 5.5V, 1Mbps RS-232 Transceivers with AutoShutdown PlusApplications*EP = Exposed pad.Ordering Information continued at end of data sheet.Notebook, Subnote ..
MAX3244CAI ,1microA supply current, 1Mbps, 3.0V to 5.5V, RS-232 transceiver with autoshutdown plusFeaturesThe MAX3224–MAX3227/MAX3244/MAX3245 are 3V-' 1µA Supply Current powered EIA/TIA-232 and V.2 ..
MAX3244CAI+ ,1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown PlusfeaturesTransceivers in UCSP™and high data-rate capabilities.♦♦ For Low-Voltage or Data Cable
MAX3244EAI ,1microA supply current, 1Mbps, 3.0V to 5.5V, RS-232 transceiver with autoshutdown plusApplicationsMAX3225EAP -40°C to +85°C 20 SSOPOrdering Information continued at end of data sheet.No ..
MAX3244EAI+ ,±15kV ESD-Protected, 1µA, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown PlusApplicationsOrdering Information continued at end of data sheet.Notebook, Subnotebook, and Palmtop ..
MAX3244EAI+T ,±15kV ESD-Protected, 1µA, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown PlusGeneral Description ________
MAX690AEPA ,Microprocessor Supervisory CircuitsGeneral Description _______
MAX690AEPA+ ,Microprocessor Supervisory CircuitsFeaturesThe MAX690A/MAX692A/MAX802L/MAX802M/MAX805L ● Precision Supply Voltage Monitor: reduce the ..
MAX690AESA ,Microprocessor Supervisory CircuitsFeaturesThe MAX690A/MAX692A/MAX802L/MAX802M/MAX805L ' Precision Supply-Voltage Monitor:reduce the c ..
MAX690AESA ,Microprocessor Supervisory CircuitsMAX690A/MAX692A/MAX802L/MAX802M/MAX805LBUS 19-4333; Rev 3; 9/93Microprocessor Supervisory Circuits_ ..
MAX690AESA+ ,Microprocessor Supervisory CircuitsApplications883. Devices in PDIP and SO packages are available in both ● Battery-Powered Computers ..
MAX690AESA+T ,Microprocessor Supervisory CircuitsElectrical Characteristics(V = 4.75V to 5.5V for MAX690A/MAX802L/MAX805L, V = 4.5V to 5.5V for MAX6 ..
MAX3225-MAX3244
1µA Supply Current, 3.0V to 5.5V, 1Mbps RS-232 Transceivers with AutoShutdown Plus
AVAILABLE
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown PlusAutoShutdown Plus, MegaBaud, and UCSP are trademarks
of Maxim Integrated Products, Inc.
________________General DescriptionThe MAX3224–MAX3227/MAX3244/MAX3245 are 3V-
powered EIA/TIA-232 and V.28/V.24 communications
interfaces with automatic shutdown/wakeup features
and high data-rate capabilities.
All devices achieve a 1µA supply current using Maxim’s
revolutionary AutoShutdown Plus™ feature. These
devices automatically enter a low-power shutdown
mode when the RS-232 cable is disconnected or the
transmitters of the connected peripherals are inactive,
and the UART driving the transmitter inputs is inactive
for more than 30 seconds. They turn on again when
they sense a valid transition at any transmitter or receiv-
er input. AutoShutdown Plus saves power without
changes to the existing BIOS or operating system.
The MAX3225/MAX3227/MAX3245 also feature
MegaBaud™ operation, guaranteeing 1Mbps for high-
speed applications such as communicating with ISDN
modems. The MAX3224/MAX3226/MAX3244 guarantee
250kbps operation. The transceivers have a proprietary
low-dropout transmitter output stage enabling true RS-
232 performance from a +3.0V to +5.5V supply with a
dual charge pump. The charge pump requires only four
small 0.1µF capacitors for operation from a 3.3V supply.
The MAX3224–MAX3227 feature a logic-level output
(READY) that asserts when the charge pump is regulat-
ing and the device is ready to begin transmitting.
All devices are available in a space-saving TQFN,
TSSOP, and SSOP packages.
________________________ApplicationsNotebook, Subnotebook, and Palmtop Computers
Cellular Phones
Battery-Powered Equipment
Handheld Equipment
Peripherals
Printers
_Next Generation Device Features♦
For Smaller Packaging:
MAX3228/MAX3229: +2.5V to +5.5V RS-232
Transceivers in UCSP™♦
For Low-Voltage or Data Cable Applications:
MAX3380E/MAX3381E: +2.35V to +5.5V, 1µA,
2 Tx/2 Rx RS-232 Transceivers with ±15kV ESD-
Protected I/O and Logic Pins♦
For Integrated ESD Protection:
MAX3222E/MAX3232E/MAX3237E/MAX3241E/
MAX3246E: ±15kV ESD-Protected, Down to 10nA,
+3.0V to +5.5V, Up to 1Mbps, True RS-232
Transceivers (MAX3246E Available in UCSP)
PARTMAX3224
MAX3225
MAX32261/1
2/2
2/2
NO. OF
DRIVERS/
RECEIVERS
READY
OUTPUT
Auto-
Shutdown
Plus250k
250k
GUARANTEED
DATA RATE
(bps)MAX3227
MAX3244
MAX32453/5
3/5
1/1✔1M
250k
_____________________Selector Guide
_______________Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX3224CPP+ 0°C to +70°C 20 PDIP MAX3224CAP+ 0°C to +70°C 20 SSOP
MAX3224CTP+ 0°C to +70°C 20 TQFN-EP*
MAX3224CUP+ 0°C to +70°C 20 TSSOP
MAX3224EPP+ -40°C to +85°C 20 PDIP
MAX3224EAP+ -40°C to +85°C 20 SSOP
MAX3224ETP+ -40°C to +85°C 20 TQFN-EP*
MAX3224EUP+ -40°C to +85°C 20 TSSOP
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Ordering Information continued at end of data sheet.MAX3224–MAX3227/
MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA= TMINto TMAX,
unless otherwise noted. Typical values are at TA= +25°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.
VCCto GND..............................................................-0.3V to +6V
V+ to GND (Note 1)..................................................-0.3V to +7V
V- to GND (Note 1)...................................................+0.3V to -7V
V+ +V-(Note 1)................................................................+13V
Input Voltages
T_IN, FORCEON, FORCEOFFto GND................-0.3V to +6V
R_IN to GND....................................................................±25V
Output Voltages
T_OUT to GND.............................................................±13.2V
R_OUT, INVALID, READY to GND.........-0.3V to (VCC+ 0.3V)
Short-Circuit Duration
T_OUT to GND.......................................................Continuous
Continuous Power Dissipation (TA= +70°C)
16-Pin SSOP (derate 7.14mW/°C above +70°C).........571mW
20-PinPDIP (derate 11.11mW/°C above +70°C)............889mW
20-PinTQFN (derate 21.3mW/°C above +70°C)........1702.1mW
20-Pin SSOP (derate 8.00mW/°C above +70°C).........640mW
20-Pin TSSOP (derate 7.00mW/°C above +70°C).......559mW
28-Pin SO (W) (derate 12.5mW/°C above +70°C).............
28-Pin SSOP (derate 9.52mW/°C above +70°C).........762mW
Operating Temperature Ranges
MAX32_ _C_ _.....................................................0°C to +70°C
MAX32_ _E_ _..................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
Note 1:V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
VCC= 5.0V
FORCEON = GND, FORCEOFF= VCC,
all R_IN idle, all T_IN idle= +25°C
VCC= 3.3V
T_IN, FORCEON,
FORCEOFF
CONDITIONS0.5Input Hysteresis
1.82.4V1.52.4Input Threshold High
0.81.5V0.61.2Input Threshold Low-25+25Input Voltage RangeVCC- 0.6 VCC- 0.1Output Voltage High0.4Output Voltage Low110Supply Current, Shutdown110Supply Current,
AutoShutdown Plus±0.05±10Output Leakage Current±0.01±1
Transmitter Input Hysteresis V0.52.4Input Logic Threshold High0.31Supply Current,
AutoShutdown Plus Disabled0.8Input Logic Threshold Low
UNITSMINTYPMAXSYMBOLPARAMETERFORCEOFF= GND
VCC= 5.0V
VCC= 3.3V= +25°C
R_OUT (MAX3244/MAX3245), receivers
disabled
T_IN, FORCEON, FORCEOFF
VCC= 5.0V
FORCEON = FORCEOFF= VCC, no load
T_IN, FORCEON, FORCEOFF
IOUT= -1.0mA
VCC= 3.3V
IOUT= 1.6mA
DC CHARACTERISTICS(VCC= 3.3V or 5.0V, TA= +25°C)
LOGIC INPUTS AND RECEIVER OUTPUTS
RECEIVER INPUTSInput Leakage Current
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA= TMINto TMAX,
unless otherwise noted. Typical values are at TA= +25°C.)
CONDITIONS30010MOutput Resistance±5±5.4Output Voltage Swing
UNITSMINTYPMAXSYMBOLPARAMETERFigure 4a
T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩto GND,
T1OUT and T2OUT loaded with
2.5mA each153060tAUTOSHDNReceiver or Transmitter Edge to
Transmitters Shutdown100tWUReceiver or Transmitter Edge to
Transmitters Enabled30tINVLReceiver Positive or Negative
Threshold to INVALIDLow1tINVHReceiver Positive or Negative
Threshold to INVALIDHighVCC - 0.6
INVALID, READY
(MAX3224–MAX3227)
Output Voltage High0.4
INVALID, READY
(MAX3224–MAX3227)
Output Voltage Low-0.30.3Receiver Input Threshold to
INVALIDOutput Low
-2.7V2.7Receiver Input Threshold to
INVALIDOutput High±5Transmitter Output Voltage±25Output Leakage Current
±60mAOutput Short-Circuit Current
VCC= V+ = V- = 0, transmitter outputs = ±2V
All transmitter outputs loaded with 3kΩto
ground
VCC= 5V, Figure 5b (Note 2)
VCC= 5V, Figure 5b (Note 2)
VCC= 5V, Figure 4b
VCC= 5V, Figure 4b
IOUT= -1.0mA
IOUT= -1.6mA
Figure 4a
Negative threshold
Positive threshold
VCC= 0 or 3V to 5.5V, VOUT= ±12V,
Transmitters disabled
TRANSMITTER OUTPUTS
MOUSE DRIVEABILITY(MAX3244/MAX3245)
AutoShutdown Plus(FORCEON = GND, FORCEOFF= VCC)
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
TIMING CHARACTERISTICS—MAX3224/MAX3226/MAX3244(VCC= +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA= TMINto TMAX,
unless otherwise noted. Typical values are at TA= +25°C.)
TIMING CHARACTERISTICS—MAX3225/MAX3227/MAX3245(VCC= +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA= TMINto TMAX,
unless otherwise noted. Typical values are at TA= +25°C.)
Note 2:A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds.
Note 3:Transmitter skew is measured at the transmitter zero cross points.= 150pF
to 2500pF= 150pF
to 1000pF
R_IN to R_OUT, CL= 150pF= 3kΩ, CL= 1000pF,
one transmitter switching
VCC= 3.3V, TA= +25°C,= 3kΩto 7kΩ,
measured from +3V to -3V
or -3V to +3V
Normal operation (MAX3244 only)
Normal operation (MAX3244 only)
(Note 3)
CONDITIONS0.15tPLHµs0.15tPHL
kbps250Maximum Data Rate
Receiver Propagation Delay
V/µs
Transition-Region Slew Rate200Receiver Output Enable Time200Receiver Output Disable Time100tPHL- tPLH Transmitter Skew50tPHL- tPLH Receiver Skew
UNITSMINTYPMAXSYMBOLPARAMETERVCC= 4.5V to 5.5V, RL= 3kΩ, = 1000pF, one transmitter switching
VCC= 3.0V to 4.5V, RL= 3kΩ, = 250pF, one transmitter switching= 3kΩ, CL= 1000pF,
one transmitter switching
VCC= 3.3V, TA= +25°C, = 3kΩto 7kΩ, CL= 150pF to 1000pF,
measured from +3V to -3V or -3V to +3V
(Note 3)
R_IN to R_OUT, CL= 150pF
Normal operation (MAX3245 only)
Normal operation (MAX3245 only)
CONDITIONS1000kbps
Maximum Data Rate
V/µs24150Transition-Region Slew Rate50tPHL- tPLH Receiver Skew25tPHL- tPLH Transmitter Skew0.15tPHLReceiver Propagation Delay0.15tPLH200Receiver Output Enable Time200Receiver Output Disable Time
UNITSMINTYPMAXSYMBOLPARAMETERMAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus10002000300040005000
MAX3224/MAX3226
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCEMAX3224-01
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps
VOUT+
VOUT-10002000300040005000
MAX3224/MAX3226
SLEW RATE vs. LOAD CAPACITANCEMAX3224-02
LOAD CAPACITANCE (pF)
SLEW RATE (V/-SLEW
+SLEW
FOR DATA RATES UP TO 250kbps20001000300040005000
MAX3224/MAX3226
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCEMAX3224-03
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
250kbps
120kbps
20kbps
T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps
MAX3225/MAX3227
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3224-04
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
2Mbps
2Mbps
1.5Mbps
1.5Mbps
1Mbps
1Mbps
1 TRANSMITTER AT FULL DATA RATE
1 TRANSMITTER AT 1/16 DATA RATE
(MAX3225)
LOAD = 3kΩ + CL10005001500200025003000
MAX3225/MAX3227
TRANSMITTER SKEW vs.
LOAD CAPACITANCEMAX3224-07
TRANSMITTER SKEW (ns)AVERAGE; 10 PARTS
1 TRANSMITTER AT 512kbps
1 TRANSMITTER AT 30kbps
(MAX3225)
LOAD = 3kΩ + CL5001000150020002500
MAX3225/MAX3227
SLEW RATE vs. LOAD CAPACITANCEMAX3224-05
LOAD CAPACITANCE (pF)
SLEW RATE (V/
1 TRANSMITTER AT 1Mbps
1 TRANSMITTER AT 62.5kbps (MAX3225)
-SLEW
+SLEW
MAX3225/MAX3227
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3224-06
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
2Mbps
1.5Mbps
1Mbps
1 TRANSMITTER AT FULL DATA RATE
1 TRANSMITTER AT 1/16 DATA RATE
(MAX3225)
LOAD = 3kΩ + CL
MAX3224–MAX3227
READY TURN-ON TIME
vs. TEMPERATURE
MAX3224-08
READY TURN-ON TIME (
MAX3224–MAX3227
READY TURN-OFF TIME
vs. TEMPERATURE
MAX3224-09
READY TURN-OFF TIME (ns)
__________________________________________Typical Operating Characteristics(VCC= +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩand CL, TA= +25°C, unless otherwise noted.)
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Typical Operating Characteristics (continued)(VCC= +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩand CL, TA= +25°C, unless otherwise noted.)10002000300040005000
MAX3244
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCEMAX3224-10
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps
VOUT+
VOUT-10002000300040005000
MAX3244
SLEW RATE vs. LOAD CAPACITANCEMAX3224-11
LOAD CAPACITANCE (pF)
SLEW RATE (V/20001000300040005000
MAX3244
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCELOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
250kbps
120kbps
20kbps
1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps
MAX3245
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3224-13
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
2Mbps
2Mbps
1.5Mbps
1.5Mbps
1Mbps
1Mbps
1 TRANSMITTER AT FULL DATA RATE
2 TRANSMITTERS AT 1/16 DATA RATE
MAX3245
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3224-15
SUPPLY CURRENT (mA)
2Mbps
1.5Mbps
1Mbps
1 TRANSMITTER AT FULL DATA RATE
2 TRANSMITTERS AT 1/16 DATA RATE400800120016002000
MAX3245
SLEW RATE vs. LOAD CAPACITANCEMAX3224-14
LOAD CAPACITANCE (pF)
SLEW RATE (V/
1 TRANSMITTER AT 1Mbps
2 TRANSMITTERS AT 62.5kbps100020003000
MAX3245
TRANSMITTER SKEW vs.
LOAD CAPACITANCEMAX3224-16
TRANSMITTER SKEW (ns)
MAX3224–MAX3227/MAX3244/MAX3245
_______________Detailed Description
Dual Charge-Pump Voltage Converter The MAX3224–MAX3227/MAX3244/MAX3245’s internal
power supply consists of a regulated dual charge
pump that provides output voltages of +5.5V (doubling
charge pump) and -5.5V (inverting charge pump), over
the +3.0V to +5.5V range. The charge pump operates
in discontinuous mode: if the output voltages are less
than 5.5V, the charge pump is enabled; if the output
voltages exceed 5.5V, the charge-pump is disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies.
The READY output (MAX3224–MAX3227) is low when
the charge pumps are disabled in shutdown mode. The
READY signal asserts high when V- goes below -4V.
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Pin Description
PIN
MAX3224
MAX3225
PDIP/
SSIP/
TSSOP
TQFN-
EP
MAX3226
MAX3227
MAX3244
MAX3245
NAMEFUNCTION 1 19 1 — READY Ready to Transmit Output, Active High. READY is enabled high when
V- goes below -4V and the device is ready to transmit. 1 2 28 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor 20 3 27 V+ +5.5V Generated By the Charge Pump 2 4 24 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor 3 5 1 C2+ Positive Terminal of Inverting Charge-Pump Capacitor 4 6 2 C2- Negative Terminal of Inverting Charge-Pump Capacitor 5 7 3 V- -5.5V Generated By the Charge Pump
8, 17 6, 15 13 9, 10, 11 T_OUT RS-232 Transmitter Outputs
9, 16 7, 14 8 4–8 R_IN RS-232 Receiver Inputs
10, 15 8, 13 9 15–19 R_OUT TTL/CMOS Receiver Outputs
11 9 10 21 INVALIDValid Signal Detector Output, Active Low. A logic-high indicates that
a valid RS-232 level is present on a receiver input.
12, 13 10, 11 11 12, 13, 14 T_IN TTL/CMOS Transmitter Inputs
14 12 12 23 FORCEON
Force-On Input, Active High. Drive high to override AutoShutdown
Plus, keeping transmitters and receivers on (FORCEOFF must be
high) (Table 1).
18 16 14 25 GND Ground
19 17 15 26 VCC +3.0V to +5.5V Single Supply Voltage
20 18 16 22 FORCEOFF
Force-Off Input, Active Low. Drive low to shut down transmitters,
receivers (except R2OUTB), and charge pump. This overrides
AutoShutdown Plus and FORCEON (Table 1).
— — — 20 R2OUTB TTL/CMOS Noninverting Complementary Receiver Outputs. Always
active.
— — — — EP Exposed Pad (TQFN only). Solder the exposed pad to the ground, or
leave unconnected.
MAX3224–MAX3227/MAX3244/MAX3245
RS-232 Transmitters The transmitters are inverting level translators that
convert CMOS-logic levels to 5.0V EIA/TIA-232 levels.
The MAX3224/MAX3226/MAX3244 guarantee a
250kbps data rate (1Mbps for the MAX3225/MAX3227/
MAX3245) with worst-case loads of 3kΩin parallel with
1000pF, providing compatibility with PC-to-PC com-
munication software (such as LapLink®). Transmitters
can be paralleled to drive multiple receivers. Figure 1
shows a complete system connection.
When FORCEOFFis driven to ground or when the Auto-
Shutdown Plus circuitry senses that all receiver and
transmitter inputs are inactive for more than 30sec, the
transmitters are disabled and the outputs go into a high-
impedance state. When powered off or shut down, the
outputs can be driven to ±12V. The transmitter inputs
do not have pull-up resistors. Connect unused inputs to
GND or VCC.
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown PlusMAX3244
MAX3245
I/O
CHIP
WITH
UART
CPU
RS-232
POWER-
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
Figure 1. Interface Under Control of PMUMAX3244
MAX3245
T1OUT
R2OUTB
5kΩUART
VCC
T1IN
THREE-STATED
LOGIC
TRANSITION
DETECTOR
R2IN
PROTECTION
DIODE
R2OUT
FORCEOFF = GND
VCC
PREVIOUS
RS-232
UART
SHDN = GND
VCC
VCC
GND
5kΩ
a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE RECEIVER OUTPUT IN SHUTDOWN.
b) NEW MAX3244/MAX3245: IN SHUTDOWN, R2OUTB IS USED TO MONITOR EXTERNAL DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT
PATH THROUGH THE UART’S PROTECTION DIODE.
GND
PROTECTION
DIODE
Figure 2. The MAX3244/MAX3245 detect RS-232 activity when
the UART and interface are shut down.
MAX3224–MAX3227/MAX3244/MAX3245
RS-232 Receivers The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3224–MAX3227 feature inverting
outputs that always remain active (Table 1). The
MAX3244/MAX3245 have inverting three-state outputs
that are high impedance when shut down (FORCEOFF
= GND) (Table 1).
The MAX3244/MAX3245 feature an extra, always
active, noninverting output, R2OUTB. R2OUTB output
monitors receiver activity while the other receivers are
high impedance, allowing Ring Indicator applications to
be monitored without forward biasing other devices
connected to the receiver outputs. This is ideal for sys-
tems where VCCis set to ground in shutdown to
accommodate peripherals such as UARTs (Figure 2).
The MAX3224–MAX3227/MAX3244/MAX3245 feature
an INVALIDoutput that is enabled low when no valid
RS-232 voltage levels have been detected on all receiv-
er inputs. Because INVALIDindicates the receiver
input’s condition, it is independent of FORCEON and
FORCEOFFstates (Figures 3 and 4).
AutoShutdown Plus ModeThe MAX3224–MAX3227/MAX3244/MAX3245 achieve a
1µA supplycurrentwith Maxim’s AutoShutdown Plus
feature, which operates when FORCEOFFis high and a
FORCEON is low. When these devices do not sense a
valid signal transition on any receiver and transmitter
input for 30sec, the on-board charge pumps are shut
down, reducing supply current to 1µA. This occurs if the
RS-232 cable is disconnected or if the connected
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Table 1. Output Control Truth Table
OPERATION
STATUSFORCEONFORCEOFF
VALID
RECEIVER
LEVEL
RECEIVER OR
TRANSMITTER
EDGE WITHIN
30sec
T_OUT
R_OUT
(MAX3224/
MAX3225/
MAX3226/
MAX3227)
R_OUT
(MAX3244/
MAX3245)
R2OUTB
(MAX3244/
MAX3245)Shutdown
(Forced Off)X0XXHigh-ZActiveHigh-ZActive
Normal
Operation
(Forced On)1XXActiveActiveActiveActive
Normal
Operation
(AutoShutdown
Plus)1XYesActiveActiveActiveActive
Shutdown (Auto-
Shutdown Plus)01XNoHigh-ZActiveActiveActive
Normal
Operation INVALID*1YesXActive ActiveActiveActive
Normal
OperationINVALID*1XYesActiveActiveActiveActive
ShutdownINVALID*1NoNoHigh-ZActiveActiveActive
Normal
Operation
(AutoShutdown)
INVALID*INVALID**YesXActiveActiveActiveActive
Shutdown
(AutoShutdown™)INVALID*INVALID**NoXHigh-ZActiveHigh-ZActive
X = Don’t care
*INVALIDconnected to FORCEON
**INVALIDconnected to FORCEON and FORCEOFF
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
MAX3224–MAX3227/MAX3244/MAX3245
peripheral transmitters are turned off, and the UART dri-
ving the transmitter inputs is inactive. The system turns
on again when a valid transition is applied to any
RS-232 receiver or transmitter input. As a result, the sys-
tem saves power without changes to the existing BIOS
or operating system.
Figures 3a and 3b depict valid and invalid RS-232
receiver voltage levels. INVALIDindicates the receiver
input’s condition, and is independent of FORCEON and
FORCEOFFstates. Figure 3 and Tables 1 and 2 sum-
marize the operating modes of the MAX3224–
MAX3227/MAX3244/MAX3245 devices. FORCEON and
FORCEOFFoverride AutoShutdown Plus circuitry.
When neither control is asserted, the IC selects
between these states automatically based on the last
receiver or transmitter input edge received.
When shut down, the device’s charge pumps turn off,
V+ is pulled to VCC, V- is pulled to ground, the transmit-
ter outputs are high impedance, and READY
(MAX3224–MAX3227) is driven low. The time required
to exit shutdown is typically 100µs (Figure 6).
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus+0.3V
-0.3V
INVALID
R_IN
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.30µs
TIMER
+2.7V
-2.7V
INVALID
R_IN
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.
30µs
TIMER
AUTOSHDN
R_IN
T_IN
30sec
TIMER
EDGE
DETECT
EDGE
DETECT
FORCEOFF
FORCEON
Figure 3a. INVALIDFunctional Diagram, INVALIDLow
Figure 3b. INVALIDFunctional Diagram, INVALIDHigh
Figure 3c. AutoShutdown Plus Logic
POWERDOWN*
AUTOSHDN
FORCEOFF
FORCEON
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3d. Power-Down Logic
RECEIVER INPUT LEVELS
-2.7V
-0.3V
+2.7V
+0.3V
INDETERMINATE
INVALID HIGH
INVALID LOW
INVALID HIGH
INDETERMINATE
Figure 4a. Receiver Positive/Negative Thresholds for INVALID
RS-232 SIGNAL
PRESENT AT ANY
RECEIVER INPUTINVALID
OUTPUTYesHighLow
Table 2. INVALIDTruth TableMAX3224–MAX3227/MAX3244/MAX3245
