_______________General Description
The MAX3238 true RS-232 transceiver achieves a 1µA supply current with Maxim’s revolutionary AutoShutdown Plus™ feature. When the device does not n a valid signal transition on either the receiver or transmitter inputs within 30c, the on-board power supply and drivers shut down. This occurs if the RS-232cable 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-232receiver or transmitter input, saving power without changes to the existing BIOS or operating system. The MAX3238 5-driver/3-receiver complete rial 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.
Receiver R1 has an extra, always-active output (in addi-tion to its standard output), which allows external devices, such as a modem, to be monitored without for-ward biasing the protection diodes in c护垫
ircuitry that may have V CC completely removed.
The MAX3238 is available in a space-saving SSOP package.
________________________Applications
Notebook, Subnotebook, and Palmtop Computers
High-Speed Modems Battery-Powered Equipment Hand-Held Equipment Peripherals Printers
AutoShutdown Plus i s a trademark of Maxim Integrated Products.*Patents Pending
____________________________Features
o 1µA Supply Current Achieved with AutoShutdown Plus o Guaranteed Data Rate: 250kbps o 1µA Low-Power Shutdown
o Receivers Active in AutoShutdown Plus Mode o Flow-Through Pinout
o Meets EIA/TIA-232 Specifications Down to 3.0V o Guaranteed 6V/µs Slew Rate
MAX3238*
+3.0V to +5.5V , 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus
________________________________________________________________Maxim Integrated Products
1
__________________Pin Configuration
19-1144; Rev 1; 10/02
Typical Operating Circuit appears at end of data sheet.
For pricing, delivery, and ordering information,plea contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at
M A X 3238
+3.0V to +5.5V , 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus 2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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 A = T MIN to T MAX ; unless otherwi noted. Typical values are at T A = +25°C.)
千岛湖介绍Stress beyond tho listed under “Absolute Maximum Ratings” may cau permanent damage to the device. The are stress ratings only, and functional operation of the device at the or any other conditions beyond tho indicated in the operational ctions of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
V CC ...........................................................................-0.3V to +6V V+ (Note 1)...............................................................-0.3V to +7V V- (Note 1)................................................................+0.3V to -7V V+ + |V-| (Note 1).................................................................+13V Input Voltages
T_IN, FORCEOFF , .-0.3V to +6V ±25V Output Voltages
±13.2V R_OUT, INVALID ....................................-0.3V to (V CC + 0.3V)
Short-Circuit Duration
T_OUT (one at a time)............................................Continuous Continuous Power Dissipation (T A = +70°C)
SSOP (derate 9.52mW/°C above +70°C)....................762mW Operating Temperature Ranges
MAX3238CAI ......................................................0°C to +70°-40°C to +85°C Storage Temperature Range ............................-65°C to +160°C Lead Temperature (soldering, 10s) ................................+300°C
Note 1:V+ and V- can have a maximum magnitude of +7V, but their absolute difference can not exceed +13V.闺蜜结婚祝福
MAX3238
+3.0V to +5.5V , 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus
茶花的养殖方法_______________________________________________________________________________________3
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 A = T MIN to T MAX ; unless otherwi 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.
______________________________________________________________Pin Description做戒指
7.5-5.0-7.5
1000
30005000TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
-2.55.0
LOAD CAPACITANCE (pF)
T R A N S M I T T E R O U T P U T V O L T A G E (V )
2000
40002.50
安全记录
14420
100030005000SLEW RATE
vs. LOAD CAPACITANCE
612S L E W R A T E (V /µs )
LOAD CAPACITANCE (pF)
20004000
10870
20100
10003000
5000
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
3060S U P P L Y C U R R E N T (m A )
LOAD CAPACITANCE (pF)
20004000
5040__________________________________________Typical Operating Characteristics
(V CC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3k Ω, T A = +25°C, unless otherwi noted.)
M A X 3238
+3.0V to +5.5V , 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus 4_______________________________________________________________________________________
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
C1+
28
+5.5V Generated by the Charge Pump
V+27+3.0V to +5.5V Supply Voltage V CC 26NAME FUNCTION
1
C2+Positive Terminal of Inverting Charge-Pump Capacitor 2GND Ground
PIN
3C2-Negative Terminal of Inverting Charge-Pump Capacitor 4V--5.5V Generated by the Charge Pump 14FORCEOFF
Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and on-board supply. This overrides AutoShutdown Plus and FORCEON (Table 1).
13
FORCEON
Force-Off Input. Drive high to override AutoShutdown Plus, keeping transmitters and receivers on (FORCEOFF must be high) (Table 1).
8, 9, 11R_IN RS-232 Receiver Inputs (R1IN–R3IN)
5, 6, 7, 10, 12T_OUT RS-232 Transmitter Outputs (T1OUT–T5OUT)25C1-Negative Terminal of Voltage-Doubler Charge-Pump Capacitor 18, 20, 21
R_OUT TTL/CMOS Receiver Outputs (R3OUT–R1OUT)
17, 19, 22, 23, 24
T_IN TTL/CMOS Transmitter Inputs (T5IN–T1IN)16
R1OUTB Noninverting Complementary Receiver Output. Always active.15INVALID Output of the Valid Signal Detector. A logic “1” indicates if a valid RS-232 level is prent on receiver inputs.
MAX3238
+3.0V to +5.5V , 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus
_______________________________________________________________________________________5
_______________Detailed Description
Dual Charge-Pump Voltage Converter
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 rervoir capacitor (C3, C4) to generate the V+and V- supplies.
RS-232 Transmitters
The transmitters are inverting level translators that con-vert CMOS-logic levels to 5.0V EIA/TIA-232 l
evels. The MAX3238 transmitters guarantee a 250kbps data rate with worst-ca loads of 3k Ωin parallel with 1000pF ,providing compatibility with PC-to-PC communication software (such as LapLink™). Transmitters can be par-alleled to drive multiple receivers. F igure 1 shows a complete system connection.
LapLink is a trademark of Traveling Software.
When FORCEOFF is driven to ground, the transmitters and receivers are disabled and the outputs go high impedance, except for R1OUTB. When the Auto-Shutdown Plus circuitry ns that all receiver and transmitter inputs are inactive for more than 30c, 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.
The transmitter inputs do not have pull-up resistors.Connect unud inputs to GND or V CC .
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic output levels. All receivers have inverting three-state outputs and are inactive in shutdown (FORCEOFF )(Table 1). The MAX3238 also feature
s 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 V CC is t to 0V in shutdown to accommodate peripher-als, such as UARTs (Figure 2).
Table 1. Output Control Truth Table
FORCEON
F O R C E O F F
AUTOSHUTDOWN
PLUS*
OPERATION STATUS T_OUT
R_OUT
R1OUTB
X 0X
美体塑身衣Shutdown (Forced Off)High-Z High-Z Active
收养流浪猫11X Normal Operation (Forced On)Active Active Active
01<30c*Normal Operation
(AutoShutdown Plus)
Active Active Active
01>30c*Shutdown
(AutoShutdown Plus)
High-Z Active Active
X = Don’t Care
*Time since last receiver or transmitter input transition.
M A X 3238
+3.0V to +5.5V , 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus 6_______________________________________________________________________________________
AutoShutdown Plus Mode
1µA supply current is achieved with Maxim’s AutoShutdown Plus feature, which operates when FORCEOFF is high and F ORCEON is low. When the MAX3238 ns no valid signal transitions on all receiver and transmitter inputs for 30c, 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 ud in any mode (Figure 3).
Figure 1. Interface Under Control of PMU
Figure 2. The MAX3238 detects RS-232 activity when the UART and interface are shut down.
