MAX3238CAIT [MAXIM]
LINE TRANSCEIVER, PDSO28, 0.200 INCH, 0.65 MM PITCH, SSOP-28;
| 型号： | MAX3238CAIT |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | LINE TRANSCEIVER, PDSO28, 0.200 INCH, 0.65 MM PITCH, SSOP-28 |
| 文件： | 总12页 (文件大小：113K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1144; Rev 0; 9/96
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX3238 true RS-232 tra ns c e ive r a c hie ve s a
1µA s up p ly c urre nt with Ma xim’s re volutiona ry
AutoShutdown Plus feature. When the device does not
sense a valid signal transition on either the receiver or
transmitter inputs within 30sec, the on-board power
supply and drivers shut down. This occurs if the RS-232
cable is disconnected or if the transmitters of the con-
nected peripheral are inactive. The system turns on
again when a valid transition is applied to any RS-232
re c e ive r or tra ns mitte r inp ut, s a ving p owe r without
changes to the existing BIOS or operating system.
♦ 1µA Supply Current Achieved with
AutoShutdown Plus
♦ Guaranteed Data Rate: 250kbps
♦ 1µA Low-Power Shutdown
♦ Receivers Active in AutoShutdown Plus Mode
♦ Flow-Through Pinout
*
♦ Meets EIA/TIA-232 Specifications Down to 3.0V
♦ Guaranteed 6V/µs Slew Rate
The MAX3238 5-driver/3-receiver complete serial port is
a 3V-powered EIA/TIA-232 and V.28/V.24 communica-
tions interface intended for notebook or subnotebook
computer applications. A proprietary, high-efficiency,
dual charge-pump power supply and a low-dropout
transmitter combine to deliver true RS-232 performance
from a single +3.0V to +5.5V supply. A guaranteed
data rate of 250kbps provides compatibility with popu-
lar software for communicating with personal comput-
ers. The MAX3238 requires only 0.1µF capacitors in
3.3V operation. It is ideal for 3.3V-only systems, mixed
3.3V and 5.0V systems, or 5V-only systems that require
true RS-232 performance.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
28 SSOP
MAX3238CAI
MAX3238EAI
-40°C to +85°C
28 SSOP
Receiver R1 has an extra, always-active output (in addi-
tion to its s ta nd a rd outp ut), whic h a llows e xte rna l
devices, such as a modem, to be monitored without for-
ward biasing the protection diodes in circuitry that may
__________________P in Co n fig u ra t io n
have V completely removed.
CC
TOP VIEW
The MAX3238 is available in a space-saving SSOP
package.
C2+
GND
C2-
V-
28
27
26
25
24
23
22
1
2
C1+
V+
________________________Ap p lic a t io n s
V
CC
3
Notebook, Subnotebook, and Palmtop
Computers
C1-
4
T1IN
T2IN
T3IN
T1OUT
T2OUT
5
High-Speed Modems
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
MAX3238
6
T3OUT
R1IN
7
21 R1OUT
8
9
20
R2IN
R2OUT
Printers
19
10
11
12
13
14
T4IN
18 R3OUT
T5IN
T4OUT
R3IN
Typical Operating Circuit appears at end of data sheet.
17
T5OUT
FORCEON
FORCEOFF
16 R1OUTB
15
INVALID
AutoShutdown Plus
*Patents Pending
is a trademark of Maxim Integrated Products.
SSOP
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
ABSOLUTE MAXIMUM RATINGS
V
CC
...........................................................................-0.3V to +6V
Short-Circuit Duration
V+ (Note 1)...............................................................-0.3V to +7V
V- (Note 1) ................................................................+0.3V to -7V
V+ + |V-| (Note 1).................................................................+13V
Input Voltages
T_OUT (one at a time)............................................Continuous
Continuous Power Dissipation (T = +70°C)
A
SSOP (derate 9.52mW/°C above +70°C) ....................762mW
Operating Temperature Ranges
T_IN, FORCEOFF, FORCEON..............................-0.3V to +6V
R_IN .................................................................................±25V
Output Voltages
MAX3238CAI ......................................................0°C to +70°C
MAX3238EAI....................................................-40°C to +85°C
Storage Temperature Range ............................-65°C to +160°C
Lead Temperature (soldering, 10sec) ............................+300°C
T_OUT...........................................................................±13.2V
MAX238
R_OUT, INVALID ....................................-0.3V to (V + 0.3V)
CC
Note 1: V+ and V- can have a maximum magnitude of +7V, but their absolute difference can not 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
(V
CC
= +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF and
C2–C4 = 0.33µF (tested at 5.0V ±10%); T = T
to T
; unless otherwise noted. Typical values are at T = +25°C.)
A
MIN
MAX
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS
V
= 3.3V or 5.0V, T = +25°C, receivers idle,
A
CC
1.0
1.0
0.5
10
10
transmitters idle, FORCEON = GND,
FORCEOFF = V
Supply Current, AutoShutdown Plus
µA
CC
Supply Current, Shutdown
µA
FORCEOFF = GND, T = +25°C
A
Supply Current, AutoShutdown Plus
Disabled
2.0
mA
FORCEON = FORCEOFF = V , no load
CC
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
0.8
V
V
T_IN, FORCEON, FORCEOFF
V
= 3.3V
= 5.0V
2.0
2.4
CC
Input Logic Threshold High
V
CC
Input Leakage Current
Output Leakage Current
Output Voltage Low
±0.01
±0.05
±1.0
±10
0.4
µA
µA
V
T_IN, FORCEON, FORCEOFF
Receivers disabled
I
= 1.6mA
OUT
V
0.6
-
V
0.1
-
CC
CC
Output Voltage High
I
= -1.0mA
V
OUT
RECEIVER INPUTS
Input Voltage Range
-25
0.6
0.8
25
V
V
V
= 3.3V
= 5.0V
= 3.3V
= 5.0V
1.2
1.5
1.5
1.8
0.3
5
CC
Input Threshold Low
Input Threshold High
V
CC
V
CC
2.4
2.4
V
V
CC
Input Hysteresis
Input Resistance
V
T
A
= +25°C
3
7
kΩ
2
_______________________________________________________________________________________
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF and
C2–C4 = 0.33µF (tested at 5.0V ±10%); T = T
to T
; unless otherwise noted. Typical values are at T = +25°C.)
A
MIN
MAX
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
AutoShutdown (FORCEON = GND, FORCEOFF = V
)
CC
Positive threshold
Negative threshold
2.7
Receiver Input Threshold to
INVALID Output High
Figure 7a
Figure 4a
V
-2.7
-0.3
Receiver Input Threshold to
INVALID Output Low
0.3
0.4
V
V
V
I
= 1.6mA
INVALID Output Voltage Low
OUT
V
CC -
0.6
I
= -1.0mA
INVALID Output Voltage High
OUT
Receiver Positive or Negative
V
= 5V, Figure 4b
= 5V, Figure 4b
0.1
µs
CC
Threshold to INVALID High (t
)
INVH
Receiver Positive or Negative
V
CC
50
25
30
µs
µs
Threshold to INVALID Low (t
)
INVL
Receiver or Transmitter Edge to
Transmitters Enabled (t
V
CC
= 5V, Figure 4b (Note 2)
)
WU
Receiver or Transmitter Edge to
Shutdown (t
Figure 4b (Note 2)
15
60
sec
)
AUTOSHDN
TRANSMITTER OUTPUTS
Output Voltage Swing
Output Resistance
All transmitter outputs loaded with 3kΩ to ground
±5.0
300
±5.4
10M
±35
±40
V
V
CC
= V+ = V- = GND, T = 2V
OUT
Ω
V
CC
≤ 3.6V
±60
Output Short-Circuit Current
Output Leakage Current
mA
µA
V
CC
> 3.6V
±100
V
OUT
= ±12V, V = 0V to 5.5V,
CC
±25
transmitters disabled
TIMING CHARACTERISTICS
Maximum Data Rate
R
= 3kΩ, C = 1000pF, one transmitter switching
250
kbps
µs
L
L
t
0.15
0.15
200
200
100
50
PHL
PLH
R_IN to R_OUT,
= 150pF
Receiver Propagation Delay
C
L
t
Receiver Output Enable Time
Receiver Output Disable Time
Transmitter Skew
Normal operation
Normal operation
ns
ns
ns
ns
| t
| t
- t
|
|
PHL PLH
Receiver Skew
- t
PHL PLH
V
= 3.3V,
= +25°C,
= 3Ω to 7kΩ,
CC
C
C
= 150pF to 1000pF
= 150pF to 2500pF
6
4
30
30
L
L
T
A
Transition-Region Slew Rate
R
L
V/µs
measured from +3V to
-3V or -3V to +3V
Note 2: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds.
_______________________________________________________________________________________
3
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, T = +25°C, unless otherwise noted.)
CC
A
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
SLEW RATE
vs. LOAD CAPACITANCE
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
7.5
14
12
70
60
V
+
OUT
–SLEW
5.0
250kbps
+SLEW
50
40
30
10
8
2.5
0
MAX238
FOR DATA RATES UP TO 250kbps
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
120kbps
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
6
LOADED 3kΩ + C
L
LOADED 3kΩ + C
L
-2.5
-5.0
-7.5
20
10
0
4
2
0
V
–
OUT
20kbps
0
1000
2000 3000
4000
5000
0
1000
2000
3000
4000
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
______________________________________________________________P in De s c rip t io n
PIN
NAME
C2+
FUNCTION
Positive Terminal of Inverting Charge-Pump Capacitor
Ground
1
2
GND
C2-
3
4
Negative Terminal of Inverting Charge-Pump Capacitor
-5.5V Generated by the Charge Pump
RS-232 Transmitter Outputs (T1OUT–T5OUT)
RS-232 Receiver Inputs (R1IN–R3IN)
V-
5, 6, 7, 10, 12
8, 9, 11
T_OUT
R_IN
Force-Off Input. Drive high to override AutoShutdown Plus, keeping transmitters and
receivers on (FORCEOFF must be high) (Table 1).
13
14
15
FORCEON
FORCEOFF
INVALID
Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and on-
board supply. This overrides AutoShutdown Plus and FORCEON (Table 1).
Output of the Valid Signal Detector. A logic “1” indicates if a valid RS-232 level is present
on receiver inputs.
16
R1OUTB
T_IN
Noninverting Complementary Receiver Output. Always active.
TTL/CMOS Transmitter Inputs (T5IN–T1IN)
17, 19, 22, 23, 24
18, 20, 21
R_OUT
C1-
TTL/CMOS Receiver Outputs (R3OUT–R1OUT)
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
+3.0V to +5.5V Supply Voltage
25
26
27
28
V
CC
V+
C1+
+5.5V Generated by the Charge Pump
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
4
_______________________________________________________________________________________
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
Table 1. Output Control Truth Table
AUTOSHUTDOWN
PLUS*
OPERATION
STATUS
FORCEON
FORCEOFF
T_OUT
R_OUT
R1OUTB
Shutdown
(Forced Off)
X
1
0
1
X
X
High-Z
Active
High-Z
Active
Active
Active
Normal Operation
(Forced On)
Normal
Operation
(AutoShutdown
Plus)
0
1
1
<30sec*
>30sec*
Active
Active
Active
Active
Active
Shutdown
(AutoShutdown
Plus)
0
High-Z
X = Don’t Care
* Time since last receiver or transmitter input transition.
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs go high
imp e d a nc e , e xc e p t for R1OUTB. Whe n 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, but the receivers remain active.
When the power is off, the MAX3238 permits the out-
puts to be driven up to ±12V.
_______________De t a ile d De s c rip t io n
Du a l Ch a rg e -P u m p Vo lt a g e Co n ve rt e r
The MAX3238’s internal power supply consists of a reg-
ulated dual charge pump that provides output voltages
of +5.5V (doubling charge pump) and -5.5V (inverting
charge pump), regardless of the input voltage (V
)
CC
over the 3.0V to 5.5V range. The charge pumps operate
in a discontinuous mode: if the output voltages are less
than 5.5V, the charge pumps are enabled; if the output
voltages exceed 5.5V, the charge pumps are disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies.
The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or V
.
CC
RS -2 3 2 Re c e ive rs
The receivers convert RS-232 signals to CMOS-logic
output levels. All receivers have inverting three-state
outp uts a nd a re ina c tive in shutdown (FORCEOFF)
(Table 1). The MAX3238 also features an extra, always-
active noninverting output, R1OUTB. This extra output
monitors receiver activity while the other receivers are
high impedance, allowing Ring Indicator to be moni-
tored without forward biasing other devices connected
to the receiver outputs. This is ideal for systems where
RS -2 3 2 Tra n s m it t e rs
The transmitters are inverting level translators that con-
vert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The
MAX3238 transmitters guarantee a 250kbps data rate
with worst-case loads of 3kΩ in parallel with 1000pF,
providing compatibility with PC-to-PC communication
software (such as LapLink™). Transmitters can be par-
alleled to drive multiple receivers. Figure 1 shows a
complete system connection.
V
CC
is set to 0V in shutdown to accommodate peripher-
als, such as UARTs (Figure 2).
LapLink is a trademark of Traveling Software.
_______________________________________________________________________________________
5
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
V
CC
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
PROTECTION
DIODE
PREVIOUS
RS-232
V
CC
MAX3238
T1
I
3
Rx
Tx
5k
UART
T2
T3
GND
SHDN = GND
I/O
T4
CHIP
WITH
UART
CPU
RS-232
T5
R1
R2
(a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
V
CC
TO
µP
LOGIC
TRANSITION
DETECTOR
R3
I
MAX3238
PROTECTION
DIODE
R1OUTB
Figure 1. Interface Under Control of PMU
V
CC
Au t o S h u t d o w n P lu s Mo d e
1µA s up p ly c urre nt is a c hie ve d with Ma xim’s
AutoShutd own Plus fe a ture , whic h op e ra te s whe n
FORCEOFF is low and FORCEON is high. When the
MAX3238 s e ns e s no va lid s ig na l tra ns itions on a ll
receiver and transmitter inputs for 30sec, the on-board
power supply and drivers are shut off, reducing supply
current to 1µA. This occurs if the RS-232 cable is dis-
connected or if the connected peripheral transmitters
are turned off. The system turns on again when a valid
transition is applied to any RS-232 receiver or transmit-
ter input. As a result, the system saves power without
changes to the existing BIOS or operating system. The
INVALID output is high when the receivers are active.
Since INVALID indicates the receiver inputs’ condition,
it can be used in any mode (Figure 3).
R1IN
Rx
R1OUT
THREE-STATED
UART
5k
T1OUT
T1IN
Tx
GND
FORCEOFF = GND
(b) NEW MAX3238: IN SHUTDOWN, R1OUTB IS USED TO MONITOR EXTERNAL
DEVICES AND R1OUT IS THREE STATED, ELIMINATING A CURRENT PATH
THROUGH THE UART'S PROTECTION DIODE.
Figure 2. The MAX3238 detects RS-232 activity when the
UART and interface are shut down.
6
_______________________________________________________________________________________
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
INVALID
Table 2.
Truth Table
+0.3V
RS-232 SIGNAL PRESENT AT
ANY RECEIVER INPUT
INVALID OUTPUT
R_IN
30µs
TIMER
R
INVALID
Yes
No
H
L
-0.3V
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.
Figure 3a. INVALID Functional Diagram, INVALID Low
Tables 1 and 2 and Figure 3 summarize the MAX3238’s
operating modes. FORCEON and FORCEOFF override
the automatic circuitry and force the transceiver into its
normal operating state or into its low-power standby
state. When neither control is asserted, the IC enters
AutoShutdown Plus mode and selects between these
s ta te s a utoma tic a lly, b a s e d on the la s t re c e ive r or
transmitter input edge received.
+2.7V
R_IN
30µs
TIMER
R
INVALID
-2.7V
When shut down, the device’s charge pumps turn off,
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.
V+ decays to V
V- decays to ground, and the trans-
CC,
mitter outputs are disabled (high impedance). The time
required to exit shutdown is typically 25µs (Figure 4b).
Figure 3b. INVALID Functional Diagram, INVALID High
S o ft w a re -Co n t ro lle d S h u t d o w n
If direct software control is desired, use INVALID to
indicate DTR or Ring Indicator signal. Tie FORCEOFF
and FORCEON together to bypass the AutoShutdown
feature so the line acts like a SHDN input.
EDGE
T_IN
FORCEOFF
DETECT
S
AUTOSHDN
30sec
TIMER
__________Ap p lic a t io n s In fo rm a t io n
EDGE
DETECT
R_IN
R
Ca p a c it o r S e le c t io n
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 capaci-
tors for 3.3V operation. For other supply voltages, see
Table 3 for required capacitor values. Do not use val-
ues 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,
FORCEON
Figure 3c. AutoShutdown Plus Logic
FORCEOFF
POWERDOWN*
FORCEON
AUTOSHDN
and C , to maintain the proper ratios (C1 to the
BYPASS
other capacitors).
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3d. Power-Down Logic
_______________________________________________________________________________________
7
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
When using the minimum required capacitor values,
ma ke s ure the c a p a c itor va lue d oe s not d e g ra d e
excessively with temperature. If in doubt, use capaci-
tors with a larger nominal value. The capacitor’s equiv-
INVALID HIGH
alent series resistance (ESR), which usually rises at low
+2.7V
temperatures, influences the amount of ripple on V+
INDETERMINATE
and V-.
+0.3V
0V
Table 3. Required Minimum Capacitance
Values
MAX238
INVALID LOW
INDETERMINATE
INVALID HIGH
-0.3V
V
C1
C2, C3, C4, C
(µF)
CC
BYPASS
-2.7V
(V)
(µF)
3.0 to 3.6
3.15 to 3.6
4.5 to 5.5
3.0 to 5.5
0.22
0.1
0.22
0.1
0.33
1
0.047
0.22
Figure 4a. Receiver Positive/Negative Thresholds for INVALID
INVALID
REGION
*
**
RECEIVER
INPUTS
VOLTAGE
TRANSMITTER
INPUTS
VOLTAGE
TRANSMITTER
OUTPUTS
VOLTAGE
V
INVALID
OUTPUT
CC
t
0
AUTOSHDN
I
t
AUTOSHDN
NVL
t
t
WU
WU
V+
V
CC
0
V-
* ALL RECEIVERS/TRANSMITTERS INACTIVE
** ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE
FORCEON = GND, FORCEOFF = V
CC
Figure 4b. AutoShutdown Plus and INVALID Timing Diagram
8
_______________________________________________________________________________________
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
P o w e r-S u p p ly De c o u p lin g
In applications that are sensitive to power-supply noise,
to ground with a capacitor of the same
va lue a s c a p a c itors C2, C3, a nd C4. Conne c t the
bypass capacitor as close to the IC as possible.
In t e rc o n n e c t io n
w it h 3 V a n d 5 V Lo g ic
The MAX3238 can directly interface with various 5V-
logic families, including ACT and HCT CMOS. See
Table 4 for more information on possible combinations
of interconnections.
decouple V
CC
Tra n s m it t e r Ou t p u t s w h e n
Ex it in g S h u t d o w n
Table 4. Logic Family Compatibility with
Various Supply Voltages
Figure 5 shows two transmitter outputs when exiting
shutdown mode. As they become active, the outputs
are shown going to opposite RS-232 levels (one trans-
mitter input is high, the other is low). Each transmitter is
loaded with 3kΩ in parallel with 2500pF. 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.
SYSTEM
V
CC
POWER-
SUPPLY
VOLTAGE
(V)
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3
5
3.3
5
Compatible with all CMOS families.
Hig h Da t a Ra t e s
The MAX3238 maintains the RS-232 ±5.0V minimum
tra ns mitte r outp ut volta g e e ve n a t hig h d a ta ra te s .
Fig ure 6 s hows a tra ns mitte r loop b a c k te s t c irc uit.
Figure 7 shows a loopback test result at 120kbps, and
Figure 8 shows the same test at 250kbps. For Figure 7,
all transmitters were driven simultaneously at 120kbps
into RS-232 loads in parallel with 1000pF. For Figure 8,
a single transmitter was driven at 250kbps, and all
transmitters were loaded with an RS-232 receiver in
parallel with 1000pF.
Compatible with all TTL and CMOS
families.
Compatible with ACT and HCT
CMOS, and with AC, HC, or
CD4000 CMOS.
5
3.3
V
CC
V
CC
C1+
V+
V-
C3*
C4
C1
C1-
FORCEON =
FORCEOFF
2V/div
C2+
MAX3238
C2
T2OUT
C2-
T_ OUT
T_ IN
2V/div
R_ IN
5k
R_ OUT
T1OUT
FORCEON
FORCEOFF
1000pF
V
CC
= 3.3V
5µs/div
V
CC
C1 - C4 = 0.1µF
GND
Figure 5. Transmitter Outputs when Exiting Shutdown or
Powering Up
*C3 CAN BE RETURNED TO V OR GND.
CC
Figure 6. Loopback Test Circuit
_______________________________________________________________________________________
9
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
5V
5V
0V
T1IN
0V
T1IN
T1OUT
R1OUT
+5V
0V
+5V
MAX238
T1OUT
0V
-5V
-5V
5V
0V
5V
0V
R1OUT
V
CC
= 3.3V
2µs/div
V
CC
= 3.3V
2µs/div
C1 - C4 = 0.1µF
= 1000pF
C1 - C4 = 0.1µF
= 1000pF
C
LOAD
C
LOAD
Figure 7. Loopback Test Result at 120kbps
Figure 8. Loopback Test Result at 250kbps
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 1404
10 ______________________________________________________________________________________
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
MAX238
__________Typ ic a l Op e ra t in g Circ u it
0.1µF
26
V
CC
28 C1+
25 C1-
V+ 27
*
0.1µF
0.1µF
0.1µF
0.1µF
MAX3238
1
3
C2+
C2-
V- 4
24 T1IN
T1OUT 5
T2OUT 6
T3OUT 7
T4OUT 10
T5OUT 12
T1
23 T2IN
T2
T3
T4
T5
22 T3IN
LOGIC
RS-232
INPUTS
OUTPUTS
19 T4IN
17 T5IN
14 FORCEOFF
AUTOSHUTDOWN PLUS
13
INVALID 15
FORCEON
16 R1OUTB
21 R1OUT
R1IN 8
5k
R1
R2
R3
LOGIC
OUTPUTS
20 R2OUT
18 R3OUT
R2IN 9
5k
RS-232
INPUTS
R3IN 11
5k
GND
2
*C3 MAY BE RETURNED TO EITHER V OR GND.
CC
______________________________________________________________________________________ 11
+3 .0 V t o +5 .5 V, 1 µA, u p t o 2 5 0 k b p s , Tru e
RS -2 3 2 Tra n s c e ive r w it h Au t o S h u t d o w n P lu s ™
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.068
MAX
0.078
0.008
0.015
0.008
MIN
1.73
0.05
0.25
0.09
MAX
1.99
0.21
0.38
0.20
A
A1 0.002
B
C
D
E
e
0.010
0.004
SEE VARIATIONS
α
2
0.205
0.209
5.20
5.38
E
H
0.0256 BSC
0.65 BSC
H
L
0.301
0.311
0.037
8˚
7.65
0.63
0˚
7.90
0.95
8˚
0.025
0˚
C
α
L
INCHES
MILLIMETERS
DIM PINS
MAX
6.33
MIN MAX MIN
0.239 0.249 6.07
0.239 0.249 6.07
0.278 0.289 7.07
0.317 0.328 8.07
0.397 0.407 10.07
e
D
D
D
D
D
14
16
20
24
28
6.33
SSOP
7.33
SHRINK
A
8.33
SMALL-OUTLINE
PACKAGE
10.33
21-0056A
B
A1
D
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
相关型号：
MAX3238E
+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with 【15kV ESD-Protected I/O and Logic Pins
MAXIM
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