Datasheet MAX3245EWI, MAX3245CWI, MAX3245CAI, MAX3226CAE, MAX3225EPP Datasheet (Maxim)

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone] ext. 3468.

________________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.

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
Cellular Phones
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers

____________________________Features

♦ 1µA Supply Current
♦ 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

MAX3224–MAX3227/MAX3244/MAX3245

†

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

________________________________________________________________

Maxim Integrated Products

1

19-1289; Rev 1; 3/98

PART

MAX3224
MAX3225
MAX3226

1/1

2/2

2/2

NO. OF

DRIVERS/

RECEIVERS

READY

OUTPUT

✔
✔
✔

AUTO-

SHUTDOWN

PLUS

✔
✔
✔

250k

1M

250k

GUARANTEED

DATA RATE

(bps)

MAX3227
MAX3244
MAX3245

3/5

3/5

1/1

✔

—
—

✔
✔
✔

1M

250k

1M

PART

MAX3224CPP

MAX3224CAP
MAX3224EPP -40°C to +85°C

0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

20 Plastic DIP
20 SSOP

20 Plastic DIP
MAX3224EAP
MAX3225CPP
MAX3225CAP 0°C to +70°C

0°C to +70°C

-40°C to +85°C 20 SSOP
20 Plastic DIP
20 SSOP

MAX3225EPP -40°C to +85°C 20 Plastic DIP
MAX3225EAP -40°C to +85°C 20 SSOP

Ordering Information continued at end of data sheet.

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.

_____________________ Selector Guide

_______________Ordering Information

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +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,

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 (V

CC

+ 0.3V)

Short-Circuit Duration

T_OUT to GND.......................................................Continuous

Continuous Power Dissipation (T

A

= +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.

VCC= 5.0V

FORCEON = GND, FORCEOFF = VCC,
all R_IN idle, all T_IN idle

TA= +25°C

VCC= 3.3V

T_IN, FORCEON,

FORCEOFF

CONDITIONS

kΩ3 5 7Input Resistance

V0.5Input Hysteresis

1.8 2.4

V

1.5 2.4

Input Threshold High

0.8 1.5

V

0.6 1.2

Input Threshold Low

V-25 +25Input Voltage Range

V

VCC- 0.6 VCC- 0.1

Output Voltage High

V0.4Output Voltage Low

µA1 10Supply Current, Shutdown

µA1 10

Supply Current,
AutoShutdown Plus

µA±0.05 ±10Output Leakage Current

µA±0.01 ±1

Transmitter Input Hysteresis V0.5

V

2.4

Input Logic Threshold High

mA0.3 1

Supply Current,
AutoShutdown Plus Disabled

V0.8Input Logic Threshold Low

2

UNITSMIN TYP MAXSYMBOLPARAMETER

FORCEOFF = GND

TA= +25°C

VCC= 5.0V

VCC= 3.3V

TA= +25°C

R_OUT (MAX3244/MAX3245), receivers
disabled

T_IN, FORCEON, FORCEOFF

VCC= 5.0V

FORCEON = FORCEOFF = VCC, no load

T_IN, FORCEON, FORCEOFF

I

OUT

= -1.0mA

VCC= 3.3V

I

OUT

= 1.6mA

DC CHARACTERISTICS (VCC= 3.3V or 5.0V, TA= +25°C)

LOGIC INPUTS AND RECEIVER OUTPUTS

RECEIVER INPUTS

Input Leakage Current

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(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= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.)

CONDITIONS

Ω300 10MOutput Resistance

V±5 ±5.4Output Voltage Swing

UNITSMIN TYP MAXSYMBOLPARAMETER

Figure 4a

T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND,
T1OUT and T2OUT loaded with

2.5mA each

sec15 30 60t

AUTOSHDN

Receiver or Transmitter Edge to
Transmitters Shutdown

µs100t

WU

Receiver or Transmitter Edge to
Transmitters Enabled

µs30t

INVL

Receiver Positive or Negative
Threshold to INVALID Low

µs1t

INVH

Receiver Positive or Negative
Threshold to INVALID High

V

V

CC

- 0.6

INVALID, READY
(MAX3224–MAX3227)
Output Voltage High

V0.4

INVALID, READY
(MAX3224–MAX3227)
Output Voltage Low

V-0.3 0.3

Receiver Input Threshold to
INVALID Output Low

-2.7

V

2.7

Receiver Input Threshold to
INVALID Output High

V±5Transmitter Output Voltage

µA±25Output Leakage Current

±60 mAOutput Short-Circuit Current

VCC= V+ = V- = 0, transmitter outputs = ±2V

All transmitter outputs loaded with 3kΩ to
ground

VCC= 5V, Figure 5b (Note 2)

VCC= 5V, Figure 5b (Note 2)

VCC= 5V, Figure 4b

VCC= 5V, Figure 4b

I

OUT

= -1.0mA

I

OUT

= -1.6mA

Figure 4a

Negative threshold

Positive threshold

VCC= 0 or 3V to 5.5V, V

OUT

= ±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

4 _______________________________________________________________________________________

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= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +25°C.)

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= T

MIN

to T

MAX

,

unless otherwise noted. Typical values are at T

A

= +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.

CL= 150pF
to 2500pF

CL= 150pF
to 1000pF

R_IN to R_OUT, CL= 150pF

RL= 3kΩ, CL= 1000pF,
one transmitter switching

VCC= 3.3V, TA= +25°C,
RL= 3kΩ to 7kΩ,
measured from +3V to -3V
or -3V to +3V

Normal operation (MAX3244 only)
Normal operation (MAX3244 only)
(Note 3)

CONDITIONS

0.15t

PLH

µs

0.15t

PHL

kbps250Maximum Data Rate

Receiver Propagation Delay

V/µs

4 30

6 30

Transition-Region Slew Rate

ns200Receiver Output Enable Time
ns200Receiver Output Disable Time
ns100



t

PHL

- t

PLH 

Transmitter Skew

ns50



t

PHL

- t

PLH 

Receiver Skew

UNITSMIN TYP MAXSYMBOLPARAMETER

VCC= 4.5V to 5.5V, RL= 3kΩ,
CL= 1000pF, one transmitter switching

VCC= 3.0V to 4.5V, RL= 3kΩ,
CL= 250pF, one transmitter switching

RL= 3kΩ, CL= 1000pF,
one transmitter switching

VCC= 3.3V, TA= +25°C,
RL= 3kΩ to 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)

CONDITIONS

1000

1000 kbps

250

Maximum Data Rate

V/µs24 150Transition-Region Slew Rate

ns50



t

PHL

- t

PLH 

Receiver Skew

ns25



t

PHL

- t

PLH 

Transmitter Skew

µs

0.15t

PHL

Receiver Propagation Delay

0.15t

PLH

ns200Receiver Output Enable Time
ns200Receiver Output Disable Time

UNITSMIN TYP MAXSYMBOLPARAMETER

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

_______________________________________________________________________________________

5

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0 1000 2000 3000 4000 5000

MAX3224/MAX3226

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3224-01

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps

V

OUT+

V

OUT-

0

2

4

6

8

10

12

14

16

0 1000 2000 3000 4000 5000

MAX3224/MAX3226

SLEW RATE vs. LOAD CAPACITANCE

MAX3224-02

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

-SLEW

+SLEW

FOR DATA RATES UP TO 250kbps

0

5

10

15

20

25

30

35

40

45

0 20001000 3000 4000 5000

MAX3224/MAX3226

OPERATING SUPPLY CURRENT

vs. LOAD CAPACITANCE

MAX3224-03

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

250kbps

120kbps

20kbps

T1 TRANSMITTING AT 250kbps
T2 (MAX3224) TRANSMITTING AT 15.6kbps

-7.5

0

-2.5

-5.0

2.5

5.0

7.5

0 1000500 1500 2000 2500

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 + C

L

0

15
10

5

20

25

30

35

40

45

50

0 1000500 1500 2000 2500 3000

MAX3225/MAX3227

TRANSMITTER SKEW vs.

LOAD CAPACITANCE

MAX3224-07

LOAD CAPACITANCE (pF)

TRANSMITTER SKEW (ns)

AVERAGE; 10 PARTS

1 TRANSMITTER AT 512kbps
1 TRANSMITTER AT 30kbps

(MAX3225)
LOAD = 3kΩ + C

L

0

80
70
60
50
40
30
20
10

0 500 1000 1500 2000 2500

MAX3225/MAX3227

SLEW RATE vs. LOAD CAPACITANCE

MAX3224-05

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

1 TRANSMITTER AT 1Mbps
1 TRANSMITTER AT 62.5kbps (MAX3225)

-SLEW

+SLEW

0

20
10

40
30

60
50

70

90
80

100

0 500 1000 1500 2000 2500

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 + C

L

20

24
22

30
28
26

36
34
32

38

-40 0 20-20 40 60 80 100

MAX3224–MAX3227

READY TURN-ON TIME

vs. TEMPERATURE

MAX3224-08

TEMPERATURE (°C)

READY TURN-ON TIME (µs)

0

200
180
160
140
120
100

80
60
40
20

-40 0 20-20 40 60 80 100

MAX3224–MAX3227

READY TURN-OFF TIME

vs. TEMPERATURE

MAX3224-09

TEMPERATURE (°C)

READY TURN-OFF TIME (ns)

__________________________________________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.)

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

6 _______________________________________________________________________________________

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.)

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0 1000 2000 3000 4000 5000

MAX3244

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3224-10

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps

V

OUT+

V

OUT-

0

4

2

8

6

12

10

14

0 1000 2000 3000 4000 5000

MAX3244

SLEW RATE vs. LOAD CAPACITANCE

MAX3224-11

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

0

30

20

10

40

50

60

0 20001000 3000 4000 5000

MAX3244

OPERATING SUPPLY CURRENT

vs. LOAD CAPACITANCE

MAX3224-12

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

250kbps

120kbps

20kbps

1 TRANSMITTER AT 250kbps
2 TRANSMITTERS AT 15.6kbps

-7.5

0

-2.5

-5.0

2.5

5.0

7.5

0 800400 1200 1600 2000

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

0

20
10

40
30

60
50

70

90
80

100

0 400 800 1200 1600 2000

MAX3245

OPERATING SUPPLY CURRENT

vs. LOAD CAPACITANCE

MAX3224-15

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

2Mbps

1.5Mbps

1Mbps

1 TRANSMITTER AT FULL DATA RATE
2 TRANSMITTERS AT 1/16 DATA RATE

0

20

10

40

30

60

50

70

0 400 800 1200 1600 2000

MAX3245

SLEW RATE vs. LOAD CAPACITANCE

MAX3224-14

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

1 TRANSMITTER AT 1Mbps
2 TRANSMITTERS AT 62.5kbps

0

15
10

5

20

25

30

35

40

45

50

0 1000 2000 3000

MAX3245

TRANSMITTER SKEW vs.

LOAD CAPACITANCE

MAX3224-16

LOAD CAPACITANCE (pF)

TRANSMITTER SKEW (ns)

_______________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.

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 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.

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

_______________________________________________________________________________________ 7

PIN

NAME

MAX3224
MAX3225

MAX3226
MAX3227

MAX3244
MAX3245

1 1 — READY

2 2 28 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
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- -5.5V generated by the charge pump
8, 17 13 9–11 T_OUT RS-232 Transmitter Outputs
9, 16 8 4–8 R_IN RS-232 Receiver Inputs

10, 15 9 15–19 R_OUT TTL/CMOS Receiver Outputs

11 10 21

INVALID

Valid Signal Detector Output, active low. A logic high indicates that a valid
RS-232 level is present on a receiver input.

12, 13 11 12–14 T_IN TTL/CMOS Transmitter Inputs

14 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 14 25 GND Ground
19 15 26 V

CC

+3.0V to +5.5V Single Supply Voltage

20 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.

Ready to Transmit Output, active high. READY is enabled high when

V- goes below -4V and the device is ready to transmit.

FUNCTION

Pin Description

LapLink is a trademark of Traveling Software.

MAX3224–MAX3227/MAX3244/MAX3245

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.

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).

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

8 _______________________________________________________________________________________

MAX3244
MAX3245

I/O
CHIP
WITH
UART

CPU

RS-232

POWER­MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER

FORCEOFF
FORCEON

INVALID

Figure 1. Interface Under Control of PMU

MAX3244
MAX3245

T1OUT

R2OUTB

Tx

5k

UART

V

CC

T1IN

THREE-STATED

LOGIC

TRANSITION

DETECTOR

R2IN

PROTECTION
DIODE

R2OUT

FORCEOFF = GND

V

CC

TO
µP

Rx

PREVIOUS

RS-232

Tx

UART

SHDN = GND

V

CC

V

CC

GND

Rx

5k

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

I

I

Figure 2. The MAX3244/MAX3245 detect RS-232 activity when
the UART and interface are shut down.

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 VCCis 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
1 µ A 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.

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

_______________________________________________________________________________________ 9

Table 1. Output Control Truth Table

OPERATION

STATUS

FORCEON

FORCEOFF

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)

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

X = Don’t care

*

INVALID connected to FORCEON

**

INVALID connected to FORCEON and FORCEOFF

MAX3224–MAX3227/MAX3244/MAX3245

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).

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

10 ______________________________________________________________________________________

+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

R

Figure 3a. INVALID Functional Diagram, INVALID Low

Figure 3b. INVALID Functional Diagram, INVALID High

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

0

INDETERMINATE

INVALID HIGH

INVALID LOW

INVALID HIGH

INDETERMINATE

Figure 4a. Receiver Positive/Negative Thresholds for INVALID

RS-232 SIGNAL

PRESENT AT ANY

RECEIVER INPUT

INVALID OUTPUT

Yes High

No Low

Table 2. INVALID Truth Table

EDGE

T_IN

DETECT

FORCEOFF

+2.7V

R_IN

-2.7V

INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.

30µs

TIMER

R

INVALID

EDGE

R_IN

DETECT

FORCEON

S

30sec

TIMER

R

AUTOSHDN

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.

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

______________________________________________________________________________________ 11

V

CC

0

0

V+

V-

V

CC

0

INVALID

OUTPUT

OUTPUT

TRANSMITTER

INPUTS

RECEIVER

INPUTS

}

INVALID
REGION

*MAX3224–MAX3227

TRANSMITTER

OUTPUTS

*V

CC

t

AUTOSHDN

t

WU

t

WU

t

INVL

t

INVH

t

AUTOSHDN

Figure 4b. AutoShutdown Plus, INVALID, and READY Timing Diagram

FORCEON

MASTER SHDN LINE

0.1µF 1M

FORCEOFF

MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245

POWER-

MANAGEMENT

UNIT

Figure 5. AutoShutdown Plus Initial Turn-On to Wake Up a
Mouse or Another System

Table 3. Required Minimum Capacitance
Values

MAX3224–MAX3227/MAX3244/MAX3245

__________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 C

BYPASS

, 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 VCCbypass 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.

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.

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

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

12 ______________________________________________________________________________________

V

CC

(V)

C2, C3, C4

(µF)

3.0 to 3.6 0.1

C1, C

BYPASS

(µF)

0.1

4.5 to 5.5 0.33

3.0 to 5.5 1

0.047

0.22

Figure 6. Transmitter Outputs when Exiting Shutdown or
Powering Up

MAX3224
MAX3225
MAX3226
MAX3227
MAX3244
MAX3245

5k

R_ IN

R_ OUT

FORCEON

C2-

C2+

C1-

C1+

V-

V+

V

CC

C4

C3*

C1

C2

C

BYPASS

V

CC

FORCEOFF

*C3 CAN BE RETURNED TO V

CC

OR GND.

T_ OUT

T_ IN

GND

V

CC

1000pF

Figure 7. Loopback Test Circuit

5V/div

0

2V/div

0

0

VCC = 3.3V
C1–C4 = 0.1µF

5µs/div

5V/div

FORCEON =
FORCEOFF

T1OUT

T2OUT
READY

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.

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.

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

______________________________________________________________________________________ 13

Figure 8. MAX3224/MAX3226/MAX3244 Loopback Test Result
at 120kbps

2µs/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

VCC = 3.3V

Figure 9. MAX3224/MAX3226/MAX3244 Loopback Test Result
at 250kbps

2µs/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

VCC = 3.3V

Figure 10. MAX3225/MAX3227/MAX3245 Loopback Test
Result at 1Mbps

200ns/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

VCC = 3.3V

Figure 11a. MAX324_ Transmitter Output Voltage vs. Load
Current per Transmitter

6
5

V

V

OUT+

OUT-

V

OUT+

V

OUT-

4

VCC = 3.0V

3
2
1
0

-1

-2
V

CC

-3

-4

TRANSMITTER OUTPUT VOLTAGE (V)

-5

-6

0 1 2 3 4 5 6 7 8 9 10

LOAD CURRENT PER TRANSMITTER (mA)

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

14 ______________________________________________________________________________________

Figure 11b. Mouse Driver Test Circuit

+V

COMPUTER SERIAL PORT

+V

-V

GND

Tx

SERIAL

MOUSE

MAX3244
MAX3245

FORCEOFF

23

R5OUT

15

R4OUT

16

R3OUT

17

R2OUT

18

R1OUT

19

R2OUTB

20

LOGIC

OUTPUTS

5k

5k

5k

5k

5k

R5IN 8

R4IN

7

R3IN

6

R2IN 5

R1IN

4

RS-232
INPUTS

GND

25

LOGIC

INPUTS

T3IN

12

T2IN

13

T1IN

14

C2-

2

C2+

1

C1-

24

C1+

28

T3OUT

11

T2OUT 10

T1OUT 9

V-

3

V+

27

V

CC

V

CC

C4

0.1µF

C3

0.1µF

0.1µF

26

C1

0.1µF

C2

0.1µF

FORCEON

INVALID

22

21

TO POWER-

MANAGEMENT

UNIT

+3.3V

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

______________________________________________________________________________________ 15

Table 4. Logic Family Compatibility with Various Supply Voltages

SYSTEM

POWER-SUPPLY

VOLTAGE (V)

COMPATIBILITY

3.3 Compatible with all CMOS families
5 Compatible with all TTL and CMOS families

VCCSUPPLY

VOLTAGE

(V)

3.3
5

5 Compatible with ACT and HCT CMOS, and with AC, HC, or CD4000 CMOS3.3

Table 5. 3.0V to 5.5V Powered RS-232 Transceivers from Maxim

PART

SUPPLY

VOLTAGE

RANGE

(V)

NO.

OF

Tx/Rx

GUARANTEED

DATA RATE

(bps)

SUPPLY

CURRENT

(µA)

MAX3241 +3.0 to +5.5 3/5 120k300
MAX3243 +3.0 to +5.5 3/5 120k1
MAX3244 +3.0 to +5.5 3/5 250k1
MAX3245 +3.0 to +5.5 3/5 1M1
MAX3232 +3.0 to +5.5 2/2 120k300
MAX3222 +3.0 to +5.5 2/2 120k300
MAX3223 +3.0 to +5.5 2/2 120k1
MAX3224 +3.0 to +5.5 2/2 250k1
MAX3225 +3.0 to +5.5 2/2 1M1
MAX3221 +3.0 to +5.5 1/1 120k1

MAX3227 +3.0 to +5.5 1/1 1M1

MAX3226 +3.0 to +5.5 1/1 250k1

AUTO-

SHUTDOWN

PLUS

—

—
Yes
Yes

—

—

—
Yes
Yes

—

Yes

Yes

AUTO-

SHUTDOWN

—

Yes

—
—
—
—

Yes

—
—

Yes

—

—

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

16 ______________________________________________________________________________________

MAX3244

MAX3245

FORCEON

23

R5OUT

15

R4OUT

16

R3OUT

17

R2OUT

18

R1OUT

19

R2OUTB

20

FORCEOFF

22

R5IN 8

R4IN

7

R3IN

6

R2IN 5

R1IN

4

GND

25

T3IN

12

T2IN

13

T1IN

14

C2-

2

C2+

1

C1-

24

C1+

28

T3OUT

11

T2OUT 10

T1OUT 9

V-

3

V+

27

V

CC

C4

0.1µF

C3

0.1µF

C1

0.1µF

C

BYPASS

0.1µF

C2

0.1µF

+3.3V

26

INVALID

21

AUTOSHUTDOWN

PLUS

MAX3226
MAX3227

FORCEON

READY

12

1

R1OUT9

FORCEOFF

16

INVALID 10

GND

14

T1IN

11

C2-

6

C2+

5

C1-

4

C1+

2

R1IN 8

T1OUT 13

V-

7

V+

3

V

CC

V

CC

C4

0.1µF

C3

0.1µF

0.1µF

15

C1

0.1µF

C2

0.1µF

C

BYPASS

C

BYPASS

+3.3V

TO POWER­MANAGEMENT
UNIT

5k

MAX3224
MAX3225

FORCEON

READY

14

1

R2OUT10

R1OUT15

FORCEOFF

20

INVALID 11

R2IN

9

GND

18

RS-232
OUTPUTS

TTL/CMOS

INPUTS

T2IN

12

T1IN

13

C2-

6

C2+

5

C1-

4

C1+

2

R1IN

16

T2OUT

8

T1OUT 17

V-

7

V+

3

V

CC

V

CC

C4

0.1µF

C3

0.1µF

0.1µF

19

C1

0.1µF

C2

0.1µF

+3.3V

RS-232
INPUTS

TO POWER­MANAGEMENT
UNIT

TTL/CMOS

OUTPUTS

5k

5k

5k

5k

5k

5k

5k

AUTOSHUTDOWN

PLUS

AUTOSHUTDOWN

PLUS

___________________________________________________Typical Operating Circuits

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

______________________________________________________________________________________ 17

16
15
14

13

12
11
10

9

1
2
3
4
5
6
7
8

READY

C1+

V+

C1-

C2+

C2-

V-

R1IN

FORCEOFF
V

CC

GND
T1OUT
FORCEON
T1IN
INVALID
R1OUT

MAX3226
MAX3227

SSOP

28
27

26
25
24
23

22

21

20
19
18
17
16
15

1
2
3
4
5
6
7
8

9
10
11
12
13
14

C1+
V+
V

CC

GND
C1­FORCEON
FORCEOFF
INVALID
R2OUTB
R1OUT
R2OUT
R3OUT
R4OUT
R5OUT

C2+
C2-

V­R1IN
R2IN
R3IN
R4IN
R5IN

T1OUT
T2OUT
T3OUT

T3IN
T2IN
T1IN

SO/SSOP

MAX3244
MAX3245

20
19
18
17
16

15
14
13

1
2
3
4
5
6
7
8

FORCEOFF
V

CC

GND
T1OUT

C1-

V+

C1+

READY

R1IN
R1OUT

FORCEON
T1IN

T2OUT

V-

C2-

C2+

12

11

9

10

T2IN
INVALIDR2OUT

R2IN

DIP/SSOP

MAX3224
MAX3225

___________________________________________________________Pin Configurations

___________________Chip Information

MAX3224

TRANSISTOR COUNT: 1129

MAX3225

TRANSISTOR COUNT: 1129

MAX3226

TRANSISTOR COUNT: 1129

MAX3227

TRANSISTOR COUNT: 1129

MAX3244/MAX3245

TRANSISTOR COUNT: 1335

__Ordering Information (continued)

PART

MAX3227CAE

MAX3227EAE -40°C to +85°C

0°C to +70°C 16 SSOP

16 SSOP

TEMP. RANGE PIN-PACKAGE

MAX3226CAE

MAX3226EAE

MAX3244CWI

0°C to +70°C

-40°C to +85°C

0°C to +70°C 16 SSOP

16 SSOP

28 Wide SO
MAX3244CAI
MAX3244EWI
MAX3244EAI -40°C to +85°C

-40°C to +85°C

0°C to +70°C 28 SSOP

28 Wide SO

28 SSOP
MAX3245CWI

0°C to +70°C 28 Wide SO
MAX3245CAI
MAX3245EWI
MAX3245EAI -40°C to +85°C

-40°C to +85°C

0°C to +70°C 28 SSOP

28 Wide SO
28 SSOP

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,
RS-232 Transceivers with AutoShutdown Plus

18 ______________________________________________________________________________________

________________________________________________________Package Information

SSOP.EPS

MAX3224–MAX3227/MAX3244/MAX3245

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

______________________________________________________________________________________ 19

___________________________________________Package Information (continued)

SOICW.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.

___________________________________________Package Information (continued)

PDIPN.EPS