找MEMORY、二三极管上美光存储
V+VCCS1C1+C1S2C3S5C2+S6C2C4S8C2-V -GNDIL-RL-IL +RL +GNDS3C1-S4VCCS7fCLKPARTMAX202EMAX203EMAX205E–208EMAX211E/213EMAX232EMAX241EfCLK(kHz)23023020020014030Figure 4. Charge-Pump DiagramWhen in low-power shutdown mode, the MAX205E/MAX206E/MAX211E/MAX213E/MAX241E driver outputs are turned off and draw only leakage currents—even if they are back-driven with voltages between 0V and 12V. Below -0.5V in shutdown, the transmitter output is diode-clamped to ground with a 1kΩ series imped-ance.
Shutdown and Enable Control(MAX205E/MAX206E/MAX211E/MAX213E/MAX241E)
In shutdown mode, the charge pumps are turned off,V+ is pulled down to VCC, V- is pulled to ground, andthe transmitter outputs are disabled. This reduces sup-ply current typically to 1μA (15μA for the MAX213E).The time required to exit shutdown is under 1ms, asshown in Figure 5.
RS-232 Receivers
The receivers convert the RS-232 signals to CMOS-logic output levels. The guaranteed 0.8V and 2.4V receiver input thresholds are significantly tighter than the ±3V thresholds required by the EIA/TIA-232E specification. This allows the receiver inputs to respond to TTL/CMOS-logic levels, as well as RS-232 levels.
The guaranteed 0.8V input low threshold ensures that receivers shorted to ground have a logic 1 output. The 5kΩ input resistance to ground ensures that a receiver with its input left open will also have a logic 1 output. Receiver inputs have approximately 0.5V hysteresis. This provides clean output transitions, even with slow rise/fall-time signals with moderate amounts of noise and ringing.
In shutdown, the MAX213E’s R4 and R5 receivers have no hysteresis.
Receivers
All MAX213E receivers, except R4 and R5, are put intoa high-impedance state in shutdown mode (see Tables1a and 1b). The MAX213E’s R4 and R5 receivers stillfunction in shutdown mode. These two awake-in-shut-down receivers can monitor external activity while main-taining minimal power consumption.
The enable control is used to put the receiver outputs intoa high-impedance state, to allow wire-OR connection oftwo EIA/TIA-232E ports (or ports of different types) at theUART. It has no effect on the RS-232 drivers or thecharge pumps.
Note: The enable control pin is active low for theMAX211E/MAX241E (EN), but is active high for theMAX213E (EN). The shutdown control pin is active high
Integrated | 10
MAX202E–MAX213E,MAX232E/MAX241E
±15kV ESD-Protected, 5V RS-232 Transceivers
outputs. Therefore,after PC board assembly,theMachine Model is less relevant to I/O ports.
Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical forproper operation. The MAX202E, MAX206–MAX208E,MAX211E, and MAX213E require 0.1μF capacitors,and the MAX232E and MAX241E require 1μF capaci-tors, although in all cases capacitors up to 10μF canbe used without harm. Ceramic, aluminum-electrolytic,or tantalum capacitors are suggested for the 1μFcapacitors, and ceramic dielectrics are suggested forthe 0.1μF capacitors. When using the minimum recom-mended capacitor values, make sure the capacitancevalue does not degrade excessively as the operatingtemperature varies. If in doubt, use capacitors with alarger (e.g., 2x) nominal value. The capacitors’ effec-tive series resistance (ESR), which usually rises at lowtemperatures, influences the amount of ripple on V+and V-.
Use larger capacitors (up to 10μF) to reduce the outputimpedance at V+ and V-. This can be useful when“stealing” power from V+ or from V-. The MAX203E andMAX205E have internal charge-pump capacitors.
Bypass VCCto ground with at least 0.1μF. In applica-tions sensitive to power-supply noise generated by the
charge pumps, decouple VCCto ground with a capaci-tor the same size as (or larger than) the charge-pumpcapacitors (C1–C4).
V+ and V- as Power Supplies
A small amount of power can be drawn from V+ and V-,although this will reduce both driver output swing andnoise margins. Increasing the value of the charge-pumpcapacitors (up to 10μF) helps maintain performancewhen power is drawn from V+ or V-.
Driving Multiple Receivers
Each transmitter is designed to drive a single receiver.Transmitters can be paralleled to drive multiplereceivers.
Driver Outputs when Exiting Shutdown
The driver outputs display no ringing or undesirabletransients as they come out of shutdown.
High Data Rates
These transceivers maintain the RS-232 ±5.0V mini-mum driver output voltages at data rates of over120kbps. For data rates above 120kbps, refer to theTransmitter Output Voltage vs. Load Capacitancegraphs in the Typical Operating Characteristics.Communication at these high rates is easier if thecapacitive loads on the transmitters are small; i.e.,short cables are best.
Table 2. Summary of EIA/TIA-232E, V.28 Specifications
PARAMETER
0 Level1 Level
CONDITIONS
3kΩto 7kΩload3kΩto 7kΩloadNo load
3kΩ≤RL≤7kΩ, CL≤2500pF
0 Level1 Level
EIA/TIA-232E, V.28 SPECIFICA-TIONS+5V to +15V-5V to -15V±25VUp to 20kbps+3V to +15V-3V to -15V±25V
3kΩ≤RL≤7kΩ, CL≤2500pF
30V/μs100mA
V.28EIA/TIA-232E-2V < VOUT< +2V
1ms or 3% of the period4% of the period300Ω
Driver Output VoltageDriver Output Level, MaxData Rate
Receiver Input VoltageReceiver Input Level
Instantaneous Slew Rate, Max
Driver Output Short-Circuit Current, Max Transition Rate on Driver Output Driver Output Resistance
Integrated | 13
MEMORY存储芯片MAX232AESE+T中文规格书 - 图文
