+3.3V-Powered, EIA/TIA-562 Dual Transceiver with Receivers Active in Shutdown

Transcription

1 ; Rev 0; 10/9 +.Powered, EIA/TIA-5 Dual Transceiver General Description The is a +.powered EIA/TIA-5 transceiver with two transmitters and two receivers. Because it implements the EIA/TIA-5 standard, the communicates with RS- transceivers, yet consumes far less power; this makes it ideal for battery-powered, hand-held computers. And, the guarantees a 11kbps data rate while maintaining ±.V EIA/TIA-5 signal levels, which makes it compatible with LapLink software. An on-board charge pump converts the +.V supply to the ±.V needed to produce the EIA/TIA-5 output voltage levels. Four charge-pump capacitors and a bypass capacitor of similar size are the only external components required. When the s charge pumps and transmitters are shut down to save power, the receivers remain active to continuously monitor signals from external devices (for example, ring indicator from modems). The two receivers outputs can be enabled and disabled independently of the shutdown function to allow two ports generally of different types to be wire-or connected at the UART. Applications Handiterminals Battery-Powered Equipment Bar-Code Readers Notebook and Palmtop Computers Typical Operating Circuit CMOS INPUTS CMOS OUTPUTS C1 C +.V 1 C1+ VCC C+ TOP VIEW 1 18 SHDN C1+ C1- C+ C- T OUT R IN T1 OUT R1 IN R1 OUT T1 IN T IN R OUT DIP/SO C1- C- 400k T1 IN 400k T IN R1 OUT R OUT VOLTAGE DOUBLER VOLTAGE INVERTER 5k 5k C T1 OUT T OUT ALL CAPACITORS 15 8 R1 IN 14 R IN 9 18 SHDN +.V -.V C4 RS-5 OUTPUTS RS-5/RS- INPUTS ON/OFF Features Guaranteed Interoperability with RS- Operates from a Single +. to +.V Supply Drivers, Receivers Receivers Active in Shutdown Mode Low-Power Shutdown: 10µA Max Small Package 18-Pin Wide SO Three-State TTL/CMOS Receiver Outputs 11kbps Guaranteed Data Rate Ordering Information PART TEMP. RANGE PIN-PACKAGE CPN 0 C to +0 C 18 Plastic DIP CWN 0 C to +0 C 18 Wide SO C/D 0 C to +0 C Dice * * Dice are specified at T A = +5 C. Pin Configuration LapLink is a registered trademark of Traveling Software, Inc. Maxim Integrated Products 1 Call toll free for free samples or literature.

2 ABSOLUTE MAXIMUM RATINGS Power Supply Ranges Supply Voltage ( )...-0.V to +V Input Voltages T IN...-0.V to ( -0.V) R IN...±5V T OUT (Note 1)...±15V Output Voltages T OUT...±15V R OUT...-0.V to ( +0.V) Driver/Receiver Output Short Circuit to...continuous Note 1: Input voltage measured with T OUT in high-impedance state. SHDN or =. Continuous Power Dissipation (T A = +0 C) Plastic DIP...889mW Wide SO...mW Operating Temperature Range...0 C to +0 C Storage Temperature Range...-5 C to +10 C Lead Temperature (soldering, 10sec) 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. ELECTRICAL CHARACTERISTICS ( =. to.v, C1-C4 =, T A = T MIN to T MAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS RS-5 TRANSMITTERS Output Voltage Swing All transmitter outputs loaded with kω to ±. ±4.5 V Data Rate R L = kω, C L = 1000pF, T A = +5 C kbps Input Logic Threshold Low V IL 0. V Input Logic Threshold High V IH.4 V Logic Pull-Up/Input Current SHDN = 0 SHDN = ±0.01 ±1 µa Output Leakage Current =.V, SHDN =, V OUT = ±15V ±0.01 ±10 = SHDN =, V OUT = ±15V ±0.01 ±10 µa Transmitter Output Resistance = = =, V OUT = ±V 00 10M Ω Output Short-Circuit Current V OUT = ±15 ±0 ma RS-/RS-5 RECEIVERS Input Voltage Operating Range ±5 V Input Threshold Low V IL =.V 0.4 V Input Threshold High V IH =.V.4 V SHDN = =.V (no hysteresis when Input Hysteresis V SHDN = ) Input Resistance R IN 5 kω Output Voltage Low V OL I OUT =.ma V Output Voltage High V OH I OUT = -0.5mA V Output Leakage Current =, V OUT ±0.05 ±10 µa Input Threshold Low V IL 0. V Input Threshold High V IH.4 V

3 ELECTRICAL CHARACTERISTICS (continued) ( =. to.v, C1-C4 =, T A = T MIN to T MAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER SUPPLY Operating Supply Voltage.0. V Supply Current I CC No load 8 R L = kω on both outputs, inputs static 8 ma Shutdown Supply Current I CC Figure 1 T A = +5 C T A = T MIN to T MAX 50 µa SHDN Input Leakage Current 0.1 ±1 µa SHDN Threshold Low V IL 0. V SHDN Threshold High V IH.4 V AC CHARACTERISTICS C L = 50pF to 500pF, R L = kω to kω, Transition Slew Rate =.V, T A = +5 C, measured from 4 0 V/µs +V to -V or -V to +V (Note ) Transmitter Propagation Delay t PHLT 1..5 Figure t PLHT Receiver Propagation Delay t PHLR Figure (Normal Operation) t PLHR µs Receiver Propagation Delay t PHLS Figure (Shutdown) t PLHS µs Receiver-Output Enable Time t ER Figure ns Receiver-Output Disable Time t DR Figure ns Transmitter-Output Enable Time t ET Includes charge pump start-up 00 µs µs Transmitter-Output Disable Time Transmitter Propagation Delay Skew Receiver Propagation Delay Skew (Normal Operation) t DT Figure 5 00 ns t PHLT t PLHT 00 ns t PHLR t PLHR 100 ns Note : Minimum slew rate is specified with C L = 1000pF for data rates above 0kbps, corresponding with EIA/TIA-5.

4 Pin Description PIN , 15 9, 14 10, 1 11, NAME R OUT, R1 OUT FUNCTION Receiver enable. Connect to to enable receivers, and take high to disable receivers. C1+ Positive terminal of positive charge-pump capacitor. T IN, T1 IN + voltage generated by the positive charge pump. The voltage on collapses to when SHDN is low. C1- Negative terminal of positive charge-pump capacitor. C+ Positive terminal of inverting charge-pump capacitor. C- Negative terminal of inverting charge-pump capacitor. T OUT, T1 OUT R IN, R1 IN 18 SHDN - voltage generated by the inverting charge pump. The voltage on collapses to when SHDN is low. EIA/TIA-5 voltage-level transmitter outputs. These outputs are disabled (Hi-Z) when SHDN is low. EIA/TIA-5 and EIA/TIA- voltage-level receiver inputs. CMOS receiver outputs. These outputs are active regardless of the state of SHDN. They are enabled when is low, and disabled (Hi-Z) when is high. CMOS driver inputs. Ground. +. to +.V supply voltage. Shutdown control. Connect to to shut down the charge pumps and the transmitters. Take high to turn on the charge pumps and to enable the transmitters. Detailed Description The consists of three sections: charge-pump voltage converters, transmitters (drivers), and receivers. Both the transmitters and the receivers are inverting. +V to ±V, Dual Charge-Pump Voltage Converter Two charge pumps either invert or double the incoming to generate the voltages required by the transmitters. The first charge pump uses capacitor C1 to double ; the resulting voltage is stored on the reservoir capacitor. The second charge pump uses capacitor C to invert ; this negative voltage is stored on the capacitor. When SHDN is low, the charge pumps are turned off, is pulled down to by a 1kΩ resistor, and rises to. It is possible to draw some power from the and pins for external use. However, doing so diminishes the charge-pump output voltages and reduces noise margins, so it is not recommended. EIA/TIA-5 Transmitters The s drivers are inverting level translators that convert +V logic inputs to EIA/TIA-5 voltage levels. With a VCC supply of only., the driver outputs deliver the EIA/TIA-5 ±.V minimum specification under worst-case conditions when both transmitters are loaded with kω receivers (either EIA/TIA- or EIA/TIA-5). The transmitters are fast: the guaranteed data rate with standard loads is 11kbps, which is the highest rate commonly used by PC-to-PC communication software, such as LapLink. The highest practical data rate may be reduced if the other communicating device (RS-5 or RS-) is not as fast, or if the cables present an excessive capacitive load (>1000pF). Each transmitter is designed to drive a single receiver; transmitters can be paralleled to drive multiple receivers. When SHDN is low, the driver outputs are turned off. Their output leakage currents are less than 10µA when pulled to or when driven to ±15V. This enables two transmitters to be connected to the same line, provided that one of them is always disabled by taking SHDN low. 4

5 +.V I SHDN C1+ C1- C+ C- 400k INPUT OUTPUT +V t PLHT OV t PHLT OV T1 & T +.V T IN T OUT R OUT R1 & R R IN k Figure. Transmitter Propagation Delay Timing +.V DRIVE 5k +.V SHDN INPUT +V 50% 50% Figure 1. Shutdown Current Test Circuit The inputs of unused drivers may be left unconnected because they have internal 400kΩ pull-ups to VCC. Unused inputs may also be connected to or VCC, but VCC provides lower power consumption because of the internal pull-ups. OUTPUT t PHLR t PHLS 50% 50% t PLHR t PLHS EIA/TIA-5 and EIA/TIA- Receivers The s receivers convert ±.V to ±1.V EIA/TIA-5 signal levels into +V logic levels; they are rated to receive signals up to ±5V to accommodate EIA/TIA- signals as well. Both receivers invert. Their inputs are each equipped with an internal 5kΩ (nominal) terminating resistor connected to ground, and the input logic thresholds are 0.4V and.4v. The positive logic-low threshold (VIL) ensures the receiver outputs remain high whenever their inputs are left open. The receivers are active when is low, and have high-impedance outputs when is high. When SHDN is high, the receivers have hysteresis. This produces clean output transitions, even with slowmoving input signals that exhibit moderate amounts of noise and ringing. When shut down, the receivers have no hysteresis, and the propagation delay increases. Figure. Receiver Propagation Delay Timing and have hysteresis. When active in shutdown mode ( = SHDN = low), the receivers operate at reduced power and speed, and without hysteresis. The charge pumps and transmitters operate only when SHDN is high; they are unaffected by. When shut down (SHDN = low) or unpowered (VCC = ), the transmitter outputs are high impedance if they are backdriven with voltages not exceeding ±15V. The pullup resistors at the driver inputs are disconnected in shutdown mode to save power. During shutdown, is pulled down to VCC, and rises to. Shutdown and Enable Control The SHDN and controls are independent. Both receivers are always active when is low. With low and SHDN high, the receivers operate at full speed 5

6 INPUT RECEIVER OUTPUT C L = 150pF t ER - 0.V +0.4V SHDN +V t DT +.V INPUT RECEIVER OUTPUTS t DR V OH - 0.1V R L = 1kΩ V OL + 0.1V 0.5 A. TIMING DIAGRAM 1 OR 0 T X -.V Figure 4. Receiver Output Enable and Disable Timing B. TEST CIRCUIT k 50pF Applications Information Charge-Pump Capacitor Selection Normally, capacitors can be used for all locations. To reduce output ripple, increase the values of the and capacitors. If your capacitors have a very wide tolerance, consider using a nominal value a little larger than to ensure that the actual capacitance does not fall below about 80nF. For circuits designed to operate over a wide range of temperatures, consider using slightly larger capacitors to compensate for any loss of capacitance at temperature extremes. No advantage is gained by using values larger than 10µF. Power-Supply Decoupling Use a capacitor with the same value as the chargepump capacitors. Figure 5. Transmitter Output Disable Timing

7 Table 1. Summary of EIA/TIA-E/V.8 and EIA/TIA-5 Specifications PARAMETER CONDITION EIA/TIA-E/V.8 SPECIFICATION Driver Output Voltage 0 Level 1 Level kω to kω load 5. to to -15. Maximum Output Level No load ±5V Signal Rate (kω R L kω) Receiver Input Thresholds 0 Level. to Level -. to -15. Maximum Input Level ±5V Maximum Instantaneous Slew Rate Maximum Driver Output Short-Circuit Current Transition Rate on Driver Output Driver Output Resistance with Power Off C L = 500pF C L = 1000pF -V < V OUT < V Up to 0kbps Not defined /µs 100mA V.8 1ms or % of the period RS- 4% of the period 00Ω EIA/TIA-5 SPECIFICATION.V to 1.V -.V to -1.V ±1.V Up to 0kbps Up to 4kbps. to to -15. ±5V /µs 0mA 4V/µs 00Ω Table. DB9/DB5 Cable Connections Commonly Used for EIA/TIA-E, EIA/TIA-5 and V.4 Asynchronous Interfaces DB9 PIN DB5 PIN NAME SYMBOL 1 8 Received Line Signal Detector (sometimes called Data Carrier Detect) DCD Receiver Data Transmit Data RxD TxD 4 0 Data Terminal Ready DTR 5 Signal Ground Data Set Ready DSR 4 Request to Send RTS 8 5 Clear to Send CTS 9 Ring Indicator RI FUNCTION Handshake from DCE Data from DCE Data from DTE Handshake from DTE Reference point for signals Handshake from DCE Handshake from DTE Handshake from DCE Handshake from DCE

8 Chip Topography C- C1+ SHDN C1- T1 OUT C " (. mm) R1 IN R1 OUT T OUT T1 IN R OUT R T IN IN 0.00" (1.8 mm) TRANSISTOR COUNT: 189; SUBSTRATE CONNECTED TO. 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. 8 Maxim Integrated Products, 10 San Gabriel Drive, Sunnyvale, CA 9408 (408) Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.