Maxim MAX3225 1ua supply current, 1mbps, 3.0v to 5.5v, rs-232 transceivers with autoshutdown plus Datasheet

19-1289; Rev 1; 3/98
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
____________________________Features
♦ 1µA Supply Current
The MAX3225/MAX3227/MAX3245 also feature
MegaBaud™ operation, guaranteeing 1Mbps for highspeed 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 RS232 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 regulating and the device is ready to begin transmitting.
All devices are available in a space-saving SSOP package.
________________________Applications
Notebook, Subnotebook, and Palmtop Computers
♦ AutoShutdown Plus—EDN Innovation of the Year
♦ Guaranteed Data Rate:
250kbps (MAX3224/3226/3244)
1Mbps (MAX3225/3227/3245)
♦ Guaranteed Slew Rate:
6V/µs (MAX3224/3226/3244)
24V/µs (MAX3225/3227/3245)
♦ Meets EIA/TIA-232 Specifications Down to 3.0V
♦ Guaranteed Mouse Driveability (MAX3244/3245)
♦ Ready-to-Transmit Logic-Level Output
_______________Ordering Information
TEMP. RANGE
PIN-PACKAGE
MAX3224CPP
PART
0°C to +70°C
20 Plastic DIP
MAX3224CAP
MAX3224EPP
MAX3224EAP
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
20 SSOP
20 Plastic DIP
20 SSOP
MAX3225CPP
MAX3225CAP
MAX3225EPP
MAX3225EAP
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
20 Plastic DIP
20 SSOP
20 Plastic DIP
20 SSOP
Ordering Information continued at end of data sheet.
Cellular Phones
Battery-Powered Equipment
_____________________ Selector Guide
Hand-Held Equipment
Peripherals
PART
NO. OF
GUARANTEED
AUTOREADY
DRIVERS/
DATA RATE
SHUTDOWN
OUTPUT
RECEIVERS
(bps)
PLUS
Printers
MAX3224
2/2
250k
✔
✔
MAX3225
2/2
1M
✔
✔
MAX3226
1/1
250k
✔
✔
✔
MAX3227
1/1
1M
✔
MAX3244
3/5
250k
—
✔
MAX3245
3/5
1M
—
✔
AutoShutdownPlus and MegaBaud are trademarks of Maxim Integrated Products.
†Covered by U.S. Patent numbers 4,636,930; 4,679,134; 4,777,577; 4,797,899; 4,809,152; 4,897,774; 4,999,761; 5,649,210; and other patents pending.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX3224–MAX3227/MAX3244/MAX3245 †
________________General Description
The MAX3224–MAX3227/MAX3244/MAX3245 are 3Vpowered 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 receiver input. AutoShutdown Plus saves power without
changes to the existing BIOS or operating system.
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
ABSOLUTE MAXIMUM RATINGS
VCC to 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, FORCEOFF to 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-Pin Plastic DIP (derate 11.11mW/°C above +70°C) ...889mW
20-Pin SSOP (derate 8.00mW/°C above +70°C) .........640mW
28-Pin Wide SO (derate 12.5mW/°C above +70°C)........... 1W
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, 10sec) .............................+300°C
Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
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
(VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; CL = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS (VCC = 3.3V or 5.0V, TA = +25°C)
Supply Current,
AutoShutdown Plus
FORCEON = GND, FORCEOFF = VCC,
all R_IN idle, all T_IN idle
1
10
µA
Supply Current, Shutdown
FORCEOFF = GND
1
10
µA
Supply Current,
AutoShutdown Plus Disabled
FORCEON = FORCEOFF = VCC, no load
0.3
1
mA
0.8
V
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
T_IN, FORCEON, FORCEOFF
Input Logic Threshold High
T_IN, FORCEON,
FORCEOFF
VCC = 3.3V
2
VCC = 5.0V
2.4
Transmitter Input Hysteresis
V
0.5
V
Input Leakage Current
T_IN, FORCEON, FORCEOFF
±0.01
±1
µA
Output Leakage Current
R_OUT (MAX3244/MAX3245), receivers
disabled
±0.05
±10
µA
Output Voltage Low
IOUT = 1.6mA
0.4
V
Output Voltage High
IOUT = -1.0mA
VCC - 0.6 VCC - 0.1
V
RECEIVER INPUTS
Input Voltage Range
-25
Input Threshold Low
TA = +25°C
Input Threshold High
TA = +25°C
0.6
1.2
VCC = 5.0V
0.8
1.5
1.5
2.4
VCC = 5.0V
1.8
2.4
2
0.5
TA = +25°C
3
5
_______________________________________________________________________________________
V
V
VCC = 3.3V
Input Hysteresis
Input Resistance
+25
VCC = 3.3V
V
V
7
kΩ
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
(VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; CL = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TRANSMITTER OUTPUTS
Output Voltage Swing
All transmitter outputs loaded with 3kΩ to
ground
±5
±5.4
Output Resistance
VCC = V+ = V- = 0, transmitter outputs = ±2V
300
10M
Output Short-Circuit Current
VCC = 0 or 3V to 5.5V, VOUT = ±12V,
Transmitters disabled
Output Leakage Current
V
Ω
±60
mA
±25
µA
MOUSE DRIVEABILITY (MAX3244/MAX3245)
T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND,
T1OUT and T2OUT loaded with
2.5mA each
AUTOSHUTDOWN PLUS (FORCEON = GND, FORCEOFF = VCC)
Transmitter Output Voltage
Receiver Input Threshold to
INVALID Output High
Figure 4a
Receiver Input Threshold to
INVALID Output Low
Figure 4a
INVALID, READY
(MAX3224–MAX3227)
Output Voltage Low
IOUT = -1.6mA
INVALID, READY
(MAX3224–MAX3227)
Output Voltage High
IOUT = -1.0mA
±5
V
Positive threshold
Negative threshold
2.7
-2.7
-0.3
V
0.3
V
0.4
V
VCC - 0.6
V
Receiver Positive or Negative
Threshold to INVALID High
tINVH
VCC = 5V, Figure 4b
1
µs
Receiver Positive or Negative
Threshold to INVALID Low
tINVL
VCC = 5V, Figure 4b
30
µs
Receiver or Transmitter Edge to
Transmitters Enabled
tWU
VCC = 5V, Figure 5b (Note 2)
100
µs
Receiver or Transmitter Edge to
tAUTOSHDN VCC = 5V, Figure 5b (Note 2)
Transmitters Shutdown
15
30
60
sec
_______________________________________________________________________________________
3
MAX3224–MAX3227/MAX3244/MAX3245
ELECTRICAL CHARACTERISTICS (continued)
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%; CL = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Maximum Data Rate
Receiver Propagation Delay
CONDITIONS
MIN
RL = 3kΩ, CL = 1000pF,
one transmitter switching
tPHL
tPLH
TYP
MAX
250
kbps
0.15
R_IN to R_OUT, CL = 150pF
UNITS
µs
0.15
Receiver Output Enable Time
Normal operation (MAX3244 only)
200
ns
Receiver Output Disable Time
Normal operation (MAX3244 only)
200
ns
(Note 3)
100
ns
50
ns
Transmitter Skew
 tPHL - tPLH 
Receiver Skew
 tPHL - tPLH 
VCC = 3.3V, TA = +25°C,
RL = 3kΩ to 7kΩ,
measured from +3V to -3V
or -3V to +3V
Transition-Region Slew Rate
CL = 150pF
to 1000pF
6
30
CL = 150pF
to 2500pF
4
30
V/µs
TIMING CHARACTERISTICS—MAX3225/MAX3227/MAX3245
(VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; CL = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX,
unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Maximum Data Rate
Receiver Propagation Delay
tPHL
tPLH
CONDITIONS
MIN
RL = 3kΩ, CL = 1000pF,
one transmitter switching
250
VCC = 3.0V to 4.5V, RL = 3kΩ,
CL = 250pF, one transmitter switching
1000
VCC = 4.5V to 5.5V, RL = 3kΩ,
CL = 1000pF, one transmitter switching
1000
TYP
MAX
kbps
0.15
R_IN to R_OUT, CL = 150pF
UNITS
µs
0.15
Receiver Output Enable Time
Normal operation (MAX3245 only)
200
ns
Receiver Output Disable Time
Normal operation (MAX3245 only)
200
ns
(Note 3)
25
ns
50
ns
Transmitter Skew
 tPHL - tPLH 
Receiver Skew
 tPHL - tPLH 
Transition-Region Slew Rate
VCC = 3.3V, TA = +25°C,
RL = 3kΩ to 7kΩ, CL = 150pF to 1000pF,
measured from +3V to -3V or -3V to +3V
24
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.
4
_______________________________________________________________________________________
150
V/µs
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
+SLEW
8
6
VOUT3000
4000
5000
10
1000
2000
3000
4000
0
5000
MAX3225/MAX3227
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
60
80
-SLEW
50
+SLEW
40
30
1 TRANSMITTER AT 1Mbps
1 TRANSMITTER AT 62.5kbps (MAX3225)
1000
1500
2000
2500
0
500
MAX3225/MAX3227
TRANSMITTER SKEW vs.
LOAD CAPACITANCE
20
AVERAGE; 10 PARTS
15
20
1000
1500
2000
LOAD CAPACITANCE (pF)
2500
3000
1000
1500
MAX3224-06
2000
MAX3224–MAX3227
READY TURN-OFF TIME
vs. TEMPERATURE
200
MAX3224-08
26
0
500
MAX3224–MAX3227
READY TURN-ON TIME
vs. TEMPERATURE
28
22
0
LOAD CAPACITANCE (pF)
30
5
1Mbps
0
32
24
30
2500
34
10
500
2000
180
READY TURN-OFF TIME (ns)
25
1500
36
READY TURN-ON TIME (µs)
30
1000
38
MAX3224-07
1 TRANSMITTER AT 512kbps
1 TRANSMITTER AT 30kbps
(MAX3225)
LOAD = 3kΩ + CL
1.5Mbps
40
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
50
50
10
0
500
2Mbps
60
20
10
-7.5
70
2500
MAX3224-09
1Mbps
1 TRANSMITTER AT FULL DATA RATE
1 TRANSMITTER AT 1/16 DATA RATE
(MAX3225)
LOAD = 3kΩ + CL
90
SUPPLY CURRENT (mA)
70
5000
100
MAX3224-05
MAX3224-04
80
-5.0
0
4000
MAX3225/MAX3227
SLEW RATE vs. LOAD CAPACITANCE
20
35
3000
MAX3225/MAX3227
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
1 TRANSMITTER AT FULL DATA RATE
1 TRANSMITTER AT 1/16 DATA RATE
(MAX3225)
LOAD = 3kΩ + CL
1.5Mbps 1Mbps
2Mbps
40
2000
LOAD CAPACITANCE (pF)
1.5Mbps
45
1000
LOAD CAPACITANCE (pF)
2.5
0
T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps
5
0
0
2Mbps
-2.5
20kbps
15
LOAD CAPACITANCE (pF)
5.0
0
MAX3224-03
20
0
2000
120kbps
25
2
7.5
TRANSMITTER SKEW (ns)
30
FOR DATA RATES UP TO 250kbps
1000
250kbps
35
4
0
TRANSMITTER OUTPUT VOLTAGE (V)
-SLEW
10
40
SUPPLY CURRENT (mA)
SLEW RATE (V/µs)
0
-1
-2
-3
-4
-5
-6
14
12
T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps
45
MAX3224-02
VOUT+
4
3
2
1
16
MAX3224-01
6
5
MAX3224/MAX3226
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3224/MAX3226
SLEW RATE vs. LOAD CAPACITANCE
SLEW RATE (V/µs)
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3224/MAX3226
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
160
140
120
100
80
60
40
20
0
-40
-20
0
20
40
60
TEMPERATURE (°C)
80
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX3224–MAX3227/MAX3244/MAX3245
__________________________________________Typical Operating Characteristics
(VCC = +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.)
10
8
6
4
1000
2000
3000
4000
0
1000
2000
3000
4000
60
SLEW RATE (V/µs)
1Mbps
1 TRANSMITTER AT FULL DATA RATE
2 TRANSMITTERS AT 1/16 DATA RATE
2Mbps
1.5Mbps 1Mbps
4000
50
40
30
20
-5.0
10
-7.5
1 TRANSMITTER AT 1Mbps
2 TRANSMITTERS AT 62.5kbps
0
400
800
1200
1600
2000
0
400
800
1200
1600
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
MAX3245
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3245
TRANSMITTER SKEW vs.
LOAD CAPACITANCE
50
MAX3224-15
100
90
45
80
2000
MAX3224-16
0
40
70
2Mbps
60
1.5Mbps
50
40
30
1Mbps
TRANSMITTER SKEW (ns)
SUPPLY CURRENT (mA)
3000
MAX3224-14
MAX3224-13
TRANSMITTER OUTPUT VOLTAGE (V)
70
2Mbps
1.5Mbps
2000
MAX3245
SLEW RATE vs. LOAD CAPACITANCE
5.0
2.5
1000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
7.5
-2.5
0
5000
MAX3245
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
35
30
25
20
15
10
20
1 TRANSMITTER AT FULL DATA RATE
2 TRANSMITTERS AT 1/16 DATA RATE
10
5
0
0
0
400
800
1200
1600
LOAD CAPACITANCE (pF)
6
20kbps
20
0
5000
LOAD CAPACITANCE (pF)
0
120kbps
30
0
0
250kbps
40
10
2
VOUT-
1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps
50
SUPPLY CURRENT (mA)
1
0
-1
-2
-3
-4
-5
-6
12
SLEW RATE (V/µs)
1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps
60
MAX3224-11
VOUT+
4
3
2
14
MAX3224-10
6
5
MAX3244
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3244
SLEW RATE vs. LOAD CAPACITANCE
MAX3224-12
MAX3244
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
2000
0
1000
2000
LOAD CAPACITANCE (pF)
_______________________________________________________________________________________
3000
5000
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
PIN
MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245
NAME
FUNCTION
1
1
—
READY
2
2
28
C1+
3
3
27
V+
+5.5V generated by the charge pump
4
4
24
C1-
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
5
5
1
C2+
Positive Terminal of Inverting Charge-Pump Capacitor
6
6
2
C2-
Negative Terminal of Inverting Charge-Pump Capacitor
7
7
3
V-
8, 17
13
9–11
T_OUT
9, 16
8
4–8
R_IN
10, 15
9
15–19
R_OUT
11
10
21
INVALID
12, 13
11
12–14
T_IN
14
12
23
FORCEON
18
14
25
GND
Ground
19
15
26
VCC
+3.0V to +5.5V Single Supply Voltage
20
16
22
FORCEOFF
—
—
20
R2OUTB
Ready to Transmit Output, active high. READY is enabled high when
V- goes below -4V and the device is ready to transmit.
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
-5.5V generated by the charge pump
RS-232 Transmitter Outputs
RS-232 Receiver Inputs
TTL/CMOS Receiver Outputs
Valid Signal Detector Output, active low. A logic high indicates that a valid
RS-232 level is present on a receiver input.
TTL/CMOS Transmitter Inputs
Force-On Input, active high. Drive high to override AutoShutdown Plus,
keeping transmitters and receivers on (FORCEOFF must be high) (Table 1).
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).
TTL/CMOS Noninverting Complementary Receiver Outputs. Always active.
_______________Detailed Description
Dual Charge-Pump Voltage Converter
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.
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 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 3kΩ in parallel with
1000pF, providing compatibility with PC-to-PC communication software (such as LapLink™). Transmitters
can be paralleled to drive multiple receivers. Figure 1
shows a complete system connection.
RS-232 Transmitters
LapLink is a trademark of Traveling Software.
_______________________________________________________________________________________
7
MAX3224–MAX3227/MAX3244/MAX3245
Pin Description
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
POWERMANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
VCC
FORCEON
INVALID
PROTECTION
DIODE
MAX3244
MAX3245
PREVIOUS
RS-232
VCC
I
Rx
5k
UART
Tx
CPU
GND
I/O
CHIP
WITH
UART
SHDN = GND
RS-232
a)
OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
VCC
TO
µP
LOGIC
TRANSITION
DETECTOR
Figure 1. Interface Under Control of PMU
I
PROTECTION
DIODE
When FORCEOFF is driven to ground or when the AutoShutdown 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 highimpedance 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.
R2OUTB
VCC
Rx
5k
Tx
GND
b)
R2IN
R2OUT
THREE-STATED
UART
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).
MAX3244
MAX3245
T1IN
T1OUT
FORCEOFF = GND
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.
Figure 2. The MAX3244/MAX3245 detect RS-232 activity when
the UART and interface are shut down.
8
_______________________________________________________________________________________
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
RECEIVER OR
TRANSMITTER
EDGE WITHIN
30sec
T_OUT
R_OUT
(MAX3224/
MAX3225/
MAX3226/
MAX3227)
R_OUT
(MAX3244/
MAX3245)
R2OUTB
(MAX3244/
MAX3245)
FORCEON
FORCEOFF
VALID
RECEIVER
LEVEL
Shutdown
(Forced Off)
X
0
X
X
High-Z
Active
High-Z
Active
Normal
Operation
(Forced On)
1
1
X
X
Active
Active
Active
Active
Normal
Operation
(AutoShutdown
Plus)
0
1
X
Yes
Active
Active
Active
Active
Shutdown (AutoShutdown Plus)
0
1
X
No
High-Z
Active
Active
Active
Normal
Operation
INVALID*
1
Yes
X
Active
Active
Active
Active
Normal
Operation
INVALID*
1
X
Yes
Active
Active
Active
Active
Shutdown
INVALID*
1
No
No
High-Z
Active
Active
Active
Normal
Operation
(AutoShutdown)
INVALID*
INVALID**
Yes
X
Active
Active
Active
Active
Shutdown
(AutoShutdown)
INVALID*
INVALID**
No
X
High-Z
Active
High-Z
Active
OPERATION
STATUS
X = Don’t care
* INVALID connected to FORCEON
** INVALID connected to FORCEON and FORCEOFF
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 systems where V CC is set to ground in shutdown to
accommodate peripherals such as UARTs (Figure 2).
The MAX3224–MAX3227/MAX3244/MAX3245 feature
an INVALID output that is enabled low when no valid
RS-232 voltage levels have been detected on all
receiver inputs. Because INVALID indicates the receiver input’s condition, it is independent of FORCEON and
FORCEOFF states (Figures 3 and 4).
AutoShutdown Plus Mode
The MAX3224–MAX3227/MAX3244/MAX3245 achieve a
1µA supply current with Maxim’s AutoShutdown
Plusfeature, which operates when FORCEOFF is 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
peripheral transmitters are turned off, and the UART driving 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 system saves power without changes to the existing BIOS
or operating system.
_______________________________________________________________________________________
9
MAX3224–MAX3227/MAX3244/MAX3245
Table 1. Output Control Truth Table
+0.3V
T_IN
R_IN
30µs
TIMER
R
-0.3V
INVALID
R_IN
EDGE
DETECT
Figure 3a. INVALID Functional Diagram, INVALID Low
FORCEOFF
S
30sec
TIMER
EDGE
DETECT
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.
AUTOSHDN
R
FORCEON
Figure 3c. AutoShutdown Plus Logic
+2.7V
FORCEOFF
POWERDOWN*
FORCEON
R_IN
30µs
TIMER
R
-2.7V
AUTOSHDN
INVALID
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.
Figure 3b. INVALID Functional Diagram, INVALID High
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3d. Power-Down Logic
Table 2. INVALID Truth Table
INVALID HIGH
RS-232 SIGNAL
PRESENT AT ANY
RECEIVER INPUT
INVALID OUTPUT
Yes
High
No
Low
Figures 3a and 3b depict valid and invalid RS-232
receiver voltage levels. INVALID indicates the receiver
input’s condition, and is independent of FORCEON and
FORCEOFF states. Figure 3 and Tables 1 and 2 summarize the operating modes of the MAX3224–
MAX3227/MAX3244/MAX3245 devices. FORCEON and
FORCEOFF override 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 transmitter outputs are high impedance, and READY
(MAX3224–MAX3227) is driven low. The time required
to exit shutdown is typically 100µs (Figure 8).
10
+2.7V
RECEIVER INPUT LEVELS
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
INDETERMINATE
+0.3V
0
INVALID LOW
-0.3V
INDETERMINATE
-2.7V
INVALID HIGH
Figure 4a. Receiver Positive/Negative Thresholds for INVALID
By connecting FORCEON to INVALID, the MAX3224–
MAX3227/MAX3244/MAX3245 shut down when no valid
receiver level and no receiver or transmitter edge is
detected for 30sec, and wake up when a valid receiver
level or receiver or transmitter edge is detected.
By connecting FORCEON and FORCEOFF to INVALID,
the MAX3224–MAX3227/MAX3244/MAX3245 shutdown
when no valid receiver level is detected and wake up
______________________________________________________________________________________
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
INVALID
} REGION
TRANSMITTER
INPUTS
TRANSMITTER
OUTPUTS
INVALID
OUTPUT
VCC
tINVL
tINVH
0
tAUTOSHDN
tAUTOSHDN
tWU
tWU
*VCC
OUTPUT
0
V+
VCC
0
V-
*MAX3224–MAX3227
Figure 4b. AutoShutdown Plus, INVALID, and READY Timing Diagram
POWERMANAGEMENT
UNIT
MASTER SHDN LINE
0.1µF
1M
FORCEOFF FORCEON
MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245
Figure 5. AutoShutdown Plus Initial Turn-On to Wake Up a
Mouse or Another System
when a valid receiver level is detected (same functionality as AutoShutdown feature on MAX3221/MAX3223/
MAX3243).
A mouse or other system with AutoShutdown Plus may
need time to wake up. Figure 5 shows a circuit that
forces the transmitters on for 100ms, allowing enough
time for the other system to realize that the MAX3244/
MAX3245 is awake. If the other system outputs valid
RS-232 signal transitions within that time, the RS-232
ports on both systems remain enabled.
Software-Controlled Shutdown
If direct software control is desired, use INVALID to
indicate DTR or Ring Indicator signal. Tie FORCEOFF
and FORCEON together to bypass the AutoShutdown
Plus so the line acts like a SHDN input.
______________________________________________________________________________________
11
MAX3224–MAX3227/MAX3244/MAX3245
RECEIVER
INPUTS
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
__________Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. The charge pump requires 0.1µF capacitors for 3.3V operation. For other supply voltages, see
Table 3 for required capacitor values. Do not use values smaller than those listed in Table 3. Increasing the
capacitor values (e.g., by a factor of 2) reduces ripple
on the transmitter outputs and slightly reduces power
consumption. C2, C3, and C4 can be increased without
changing C1’s value. However, do not increase C1
without also increasing the values of C2, C3, C4,
and CBYPASS, to maintain the proper ratios (C1 to
the other capacitors).
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance (ESR), which usually rises at low
temperatures, influences the amount of ripple on V+
and V-.
Power-Supply Decoupling
In most circumstances, a 0.1µF VCC bypass capacitor
is adequate. In applications that are sensitive to powersupply noise, use a capacitor of the same value as
charge-pump capacitor C1. Connect bypass capacitors as close to the IC as possible.
High Data Rates
The MAX3224/MAX3226/MAX3244 maintain the RS-232
±5.0V minimum transmitter output voltage even at high
data rates. Figure 7 shows a transmitter loopback test
circuit. Figure 8 shows a loopback test result at
120kbps, and Figure 9 shows the same test at
250kbps. For Figure 8, all transmitters were driven
FORCEON =
FORCEOFF
5V/div
0
T1OUT
2V/div
0
Figure 6. Transmitter Outputs when Exiting Shutdown or
Powering Up
VCC
CBYPASS
C1, CBYPASS
(µF)
C2, C3, C4
(µF)
3.0 to 3.6
0.1
0.1
4.5 to 5.5
0.047
0.33
3.0 to 5.5
0.22
1
VCC
C1+
V+
C3*
C1
C1C2+
C2
C2-
MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245
5k
FORCEON
FORCEOFF
C4
R_ IN
R_ OUT
VCC
V-
T_ OUT
T_ IN
Table 3. Required Minimum Capacitance
Values
VCC
(V)
READY
5µs/div
Transmitter Outputs
when Exiting Shutdown
Figure 6 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter input is high; the other is low). Each
transmitter is loaded with 3kΩ in parallel with 1000pF.
The transmitter outputs display no ringing or undesirable transients as they come out of shutdown. Note that
the transmitters are enabled only when the magnitude
of V- exceeds approximately -3V.
T2OUT
VCC = 3.3V
C1–C4 = 0.1µF
5V/div
0
GND
*C3 CAN BE RETURNED TO VCC OR GND.
Figure 7. Loopback Test Circuit
12
______________________________________________________________________________________
1000pF
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
T1IN
Mouse Driveability
The MAX3244/MAX3245 are specifically designed to
power serial mice while operating from low-voltage
power supplies. They have been tested with leading
mouse brands from manufacturers such as Microsoft
and Logitech. The MAX3244/MAX3245 successfully
drove all serial mice tested and met their respective
current and voltage requirements. The MAX3244/
MAX3245 dual charge pump ensures the transmitters
will supply at least ±5V during worst-case conditions.
Figure 11a shows the transmitter output voltages under
increasing load current. Figure 11b shows a typical
mouse connection.
5V/div
T1IN
5V/div
5V/div
T1OUT
5V/div
5V/div
R1OUT
T1OUT
R1OUT
5V/div
VCC = 3.3V
VCC = 3.3V
200ns/div
2µs/div
5V/div
T1IN
5V/div
T1OUT
5V/div
R1OUT
VCC = 3.3V
2µs/div
Figure 9. MAX3224/MAX3226/MAX3244 Loopback Test Result
at 250kbps
Figure 10. MAX3225/MAX3227/MAX3245 Loopback Test
Result at 1Mbps
TRANSMITTER OUTPUT VOLTAGE (V)
Figure 8. MAX3224/MAX3226/MAX3244 Loopback Test Result
at 120kbps
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
VOUT+
VCC = 3.0V
VOUT+
VCC
VOUTVOUT-
0
1
2
3
4
5
6
7
8
9
10
LOAD CURRENT PER TRANSMITTER (mA)
Figure 11a. MAX324_ Transmitter Output Voltage vs. Load
Current per Transmitter
______________________________________________________________________________________
13
MAX3224–MAX3227/MAX3244/MAX3245
simultaneously at 120kbps into RS-232 loads in parallel
with 1000pF. For Figure 9, a single transmitter was driven at 250kbps, and all transmitters were loaded with
an RS-232 receiver in parallel with 250pF.
The MAX3225/MAX3227/MAX3245 maintain the RS-232
±5.0V minimum transmitter output voltage at data rates
up to 1Mbps (MegaBaud). Figure 10 shows a loopback
test result with a single transmitter driven at 1Mbps and
all transmitters loaded with an RS-232 receiver in parallel with 250pF.
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
+3.3V
26
0.1µF
28
C1
0.1µF
24
1
C2
0.1µF
2
LOGIC
INPUTS
VCC
27
C1+
V+
C3
0.1µF
C1C2+
MAX3244
MAX3245
COMPUTER SERIAL PORT
3
V-
C4
0.1µF
C2-
14
T1IN
T1OUT
9
+V
13
T2IN
T2OUT
10
+V
12
T3IN
T3OUT
11
-V
20
R2OUTB
19
R1OUT
GND
R1IN
4
R2IN
5
R3IN
6
R4IN
7
R5IN
8
Tx
5k
18
R2OUT
LOGIC
OUTPUTS
5k
17
R3OUT
RS-232
INPUTS
5k
16
R4OUT
5k
15
23
VCC
TO POWERMANAGEMENT
UNIT
22
21
R5OUT
SERIAL
MOUSE
5k
FORCEON
FORCEOFF
INVALID
GND
25
Figure 11b. Mouse Driver Test Circuit
14
______________________________________________________________________________________
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
Table 4. Logic Family Compatibility with Various Supply Voltages
SYSTEM
POWER-SUPPLY
VOLTAGE (V)
VCC SUPPLY
VOLTAGE
(V)
3.3
3.3
5
5
5
3.3
COMPATIBILITY
Compatible with all CMOS families
Compatible with all TTL and CMOS families
Compatible with ACT and HCT CMOS, and with AC, HC, or CD4000 CMOS
Table 5. 3.0V to 5.5V Powered RS-232 Transceivers from Maxim
PART
SUPPLY
VOLTAGE
RANGE
(V)
NO.
OF
Tx/Rx
SUPPLY
CURRENT
(µA)
AUTOSHUTDOWN
PLUS
AUTOSHUTDOWN
GUARANTEED
DATA RATE
(bps)
MAX3241
+3.0 to +5.5
3/5
300
—
—
120k
MAX3243
+3.0 to +5.5
3/5
1
—
Yes
120k
MAX3244
+3.0 to +5.5
3/5
1
Yes
—
250k
MAX3245
+3.0 to +5.5
3/5
1
Yes
—
1M
MAX3232
+3.0 to +5.5
2/2
300
—
—
120k
MAX3222
+3.0 to +5.5
2/2
300
—
—
120k
MAX3223
+3.0 to +5.5
2/2
1
—
Yes
120k
MAX3224
+3.0 to +5.5
2/2
1
Yes
—
250k
MAX3225
+3.0 to +5.5
2/2
1
Yes
—
1M
MAX3221
+3.0 to +5.5
1/1
1
—
Yes
120k
MAX3226
+3.0 to +5.5
1/1
1
Yes
—
250k
MAX3227
+3.0 to +5.5
1/1
1
Yes
—
1M
______________________________________________________________________________________
15
MAX3224–MAX3227/MAX3244/MAX3245
Interconnection with 3V and 5V Logic
The MAX3224–MAX3227/MAX3244/MAX3245 can
directly interface with various 5V logic families, including ACT and HCT CMOS. See Table 4 for more information on possible combinations of interconnections.
Table 5 lists other Maxim 3.0V to 5.5V powered transceivers.
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
___________________________________________________Typical Operating Circuits
+3.3V
+3.3V
15
0.1µF
CBYPASS
2 C1+
C1
0.1µF
4 C15
C2
0.1µF
6
C2+
3
V+
MAX3226
MAX3227
V-
9 R1OUT
C3
0.1µF
C1
0.1µF
C4
0.1µF
C2
0.1µF
7
C2-
11 T1IN
12
27
V+
C3
0.1µF
24 C11
2
C2+
MAX3244
MAX3245
V-
3
C4
0.1µF
C2-
14 T1IN
T1OUT 9
R1IN 8
13 T2IN
T2OUT 10
12 T3IN
T3OUT 11
AUTOSHUTDOWN INVALID 10
PLUS
FORCEOFF 16
FORCEON
28 C1+
VCC
T1OUT 13
5k
1 READY
26
CBYPASS
0.1µF
VCC
GND
TO POWERMANAGEMENT
UNIT
VCC
22 FORCEOFF
23 FORCEON
AUTOSHUTDOWN
PLUS
INVALID 21
20 R2OUTB
14
19 R1OUT
R1IN 4
+3.3V
CBYPASS
C1
0.1µF
2 C1+
4
5
C2
0.1µF
6
C1C2+
VCC
MAX3224
MAX3225
V-
C3
0.1µF
R3IN 6
C4
0.1µF
5k
16 R4OUT
T1OUT 17
R4IN 7
5k
RS-232
OUTPUTS
T2OUT 8
15 R5OUT
R5IN 8
5k
R1IN 16
15 R1OUT
TTL/CMOS
OUTPUTS
RS-232
INPUTS
5k
R2IN
10 R2OUT
9
GND
25
5k
1 READY
14
AUTOSHUTDOWN
PLUS
INVALID 11
FORCEOFF 20
FORCEON
GND
TO POWERMANAGEMENT
UNIT
VCC
18
16
5
5k
17 R3OUT
7
C2-
12 T2IN
R2IN
18 R2OUT
3
V+
13 T1IN
TTL/CMOS
INPUTS
5k
19
0.1µF
______________________________________________________________________________________
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
READY 1
C1+ 2
V+ 3
C1- 4
C2+ 5
MAX3226
MAX3227
C2- 6
V- 7
R1IN 8
16 FORCEOFF
C2+ 1
28 C1+
15 VCC
C2- 2
27 V+
14 GND
V- 3
26 VCC
13 T1OUT
R1IN 4
25 GND
12 FORCEON
R2IN 5
R3IN 6
10 INVALID
R4IN 7
22 FORCEOFF
9 R1OUT
R5IN 8
21 INVALID
T1OUT 9
20 R2OUTB
T2OUT 10
19 R1OUT
T3OUT 11
18 R2OUT
T3IN 12
17 R3OUT
T2IN 13
16 R4OUT
T1IN 14
15 R5OUT
20 FORCEOFF
C1+ 2
19 VCC
V+ 3
18 GND
C1- 4
C2+ 5
23 FORCEON
17 T1OUT
MAX3224
MAX3225
C2- 6
SO/SSOP
16 R1IN
15 R1OUT
V- 7
T2OUT
24 C1-
11 T1IN
SSOP
READY 1
MAX3244
MAX3245
14 FORCEON
8
13 T1IN
R2IN 9
12 T2IN
R2OUT 10
11 INVALID
DIP/SSOP
__Ordering Information (continued)
___________________Chip Information
PIN-PACKAGE
MAX3224
MAX3226CAE
0°C to +70°C
16 SSOP
TRANSISTOR COUNT: 1129
MAX3226EAE
-40°C to +85°C
16 SSOP
MAX3225
MAX3227CAE
0°C to +70°C
16 SSOP
TRANSISTOR COUNT: 1129
MAX3227EAE
MAX3244CWI
MAX3244CAI
-40°C to +85°C
0°C to +70°C
0°C to +70°C
16 SSOP
28 Wide SO
28 SSOP
MAX3244EWI
MAX3244EAI
MAX3245CWI
MAX3245CAI
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
28 Wide SO
28 SSOP
28 Wide SO
28 SSOP
MAX3245EWI
MAX3245EAI
-40°C to +85°C
-40°C to +85°C
28 Wide SO
28 SSOP
PART
TEMP. RANGE
MAX3226
TRANSISTOR COUNT: 1129
MAX3227
TRANSISTOR COUNT: 1129
MAX3244/MAX3245
TRANSISTOR COUNT: 1335
______________________________________________________________________________________
17
MAX3224–MAX3227/MAX3244/MAX3245
___________________________________________________________ Pin Configurations
________________________________________________________Package Information
SSOP.EPS
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
18
______________________________________________________________________________________
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
SOICW.EPS
______________________________________________________________________________________
19
MAX3224–MAX3227/MAX3244/MAX3245
___________________________________________Package Information (continued)
___________________________________________Package Information (continued)
PDIPN.EPS
MAX3224–MAX3227/MAX3244/MAX3245
1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.