ISL4241E, ISL4243E ® Data Sheet May 2004 QFN Packaged, ±15kV ESD Protected, +2.7V to +5.5V, 10Nanoamp, 250kbps, RS-232 Transmitters/Receivers FN8037.4 Features • Pb-free Available as an Option The Intersil ISL424XE devices are 2.7V to 5.5V powered RS-232 transmitters/receivers which meet ElA/TIA-232 and V.28/V.24 specifications, even at VCC = 3.0V. Additionally, they provide ±15kV ESD protection (IEC61000-4-2 Air Gap and Human Body Model) on transmitter outputs and receiver inputs (RS-232 pins). Targeted applications are PDAs, Palmtops, and notebook and laptop computers where the low operational, and even lower standby, power consumption is critical. Efficient on-chip charge pumps, coupled with manual and automatic powerdown functions, reduce the standby supply current to a 10nA trickle. Tiny 5mm x 5mm Quad Flat No-Lead (QFN) packaging and the use of small, low value capacitors ensure board space savings as well. Data rates greater than 250kbps are guaranteed at worst case load conditions. The ISL424XE are 3 driver, 5 receiver devices that, coupled with the 5x5 QFN package, provide the industry’s smallest, lowest power complete serial port suitable for PDAs, and laptop or notebook computers. The 5x5 QFN requires 60% less board area than a 28 lead TSSOP, and is nearly 20% thinner. The devices also include a noninverting alwaysactive receiver for “wake-up” capability. The ISL4243E features an automatic powerdown function that powers down the on-chip power-supply and driver circuits. This occurs when an attached peripheral device is shut off or the RS-232 cable is removed, conserving system power automatically without changes to the hardware or operating system. It powers up again when a valid RS-232 voltage is applied to any receiver input. Table 1 summarizes the features of the ISL424XE, while Application Note AN9863 summarizes the features of each device comprising the 3V RS-232 family. • Parameters Fully Specified for 10% Tolerance Supplies and Full Industrial Temp Range • Available in Small QFN (5mm x 5mm) Package which is 60% Smaller than a 28 Lead TSSOP • ESD Protection for RS-232 I/O Pins to ±15kV (IEC61000) • Meets EIA/TIA-232 and V.28/V.24 Specifications at 3V • RS-232 Compatible with VCC = 2.7V • On-Chip Voltage Converters Require Only Four External 0.1µF Capacitors • Manual and Automatic Powerdown Features • Receiver Hysteresis For Improved Noise Immunity • Guaranteed Minimum Data Rate . . . . . . . . . . . . . 250kbps • Wide Power Supply Range. . . . . . . Single +2.7V to +5.5V • Low Supply Current in Powerdown State . . . . . . . . . .10nA Applications • Any Space Constrained System Requiring RS-232 Ports - Battery Powered, Hand-Held, and Portable Equipment - Laptop Computers, Notebooks - PDAs and Palmtops, Data Cables - Cellular/Mobile Phones, Digital Cameras, GPS Receivers Related Literature • Technical Brief TB363 “Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices • ”Technical Brief TB379 “Thermal Characterization of Packages for ICs” • Technical Brief TB389 “PCB Land Pattern Design and Surface Mount Guidelines for QFN Packages” TABLE 1. SUMMARY OF FEATURES PART NUMBER NO. OF MONITOR Rx. NO. OF NO. OF QFN PKG. (ROUTB) Tx. Rx. AVAILABLE? DATA RATE (kbps) Rx. ENABLE FUNCTION? READY OUTPUT? MANUAL POWERDOWN? AUTOMATIC POWERDOWN FUNCTION? ISL4241E 3 5 YES 2 250 YES NO YES NO ISL4243E 3 5 YES 1 250 NO NO YES YES 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2004. All Rights Reserved All other trademarks mentioned are the property of their respective owners. ISL4241E, ISL4243E Ordering Information TEMP. RANGE (°C) PART NO. PACKAGE PKG. DWG. # ISL4241EIR -40 to 85 32 Ld QFN L32.5x5 ISL4241EIRZ (See Note) -40 to 85 32 Ld QFN (Pb-free) L32.5x5 ISL4241EIR-T -40 to 85 Tape & Reel L32.5x5 ISL4241EIRZ-T (See Note) -40 to 85 Tape & Reel (Pb-free) L32.5x5 ISL4243EIR -40 to 85 32 Ld QFN L32.5x5 ISL4243EIRZ (See Note) -40 to 85 32 Ld QFN (Pb-free) L32.5x5 ISL4243EIR-T -40 to 85 Tape & Reel L32.5x5 ISL4243EIRZ-T (See Note) -40 to 85 Tape & Reel (Pb-free) L32.5x5 NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which is compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J Std-020B. Pinouts V- C2- C2+ C1+ V+ VCC NC NC V- C2- C2+ C1+ V+ VCC NC ISL4243E (QFN) TOP VIEW NC ISL4241E (QFN) TOP VIEW 32 31 30 29 28 27 26 25 32 31 30 29 28 27 26 25 2 23 C1- R3IN 3 22 EN R3IN 3 22 FORCEON R4IN 4 21 SHDN R4IN 4 21 FORCEOFF R5IN 5 20 R1OUTB R5IN 5 20 INVALID T1OUT 6 19 R2OUTB T1OUT 6 19 R2OUTB T2OUT 7 18 R1OUT T2OUT 7 18 R1OUT T3OUT 8 17 R2OUT T3OUT 8 17 R2OUT 12 13 14 15 16 2 9 10 11 T2IN 11 T1IN 10 T2IN 9 12 13 14 15 16 NC R2IN R3OUT C1- R4OUT 23 R5OUT 2 T1IN R2IN T3IN GND NC 24 NC 1 R3OUT R1IN R4OUT GND R5OUT 24 T3IN 1 NC R1IN ISL4241E, ISL4243E Pin Descriptions PIN VCC FUNCTION System power supply input (2.7V to 5.5V). V+ Internally generated positive transmitter supply (+5.5V). V- Internally generated negative transmitter supply (-5.5V). GND Ground connection. C1+ External capacitor (voltage doubler) is connected to this lead. C1- External capacitor (voltage doubler) is connected to this lead. C2+ External capacitor (voltage inverter) is connected to this lead. C2- External capacitor (voltage inverter) is connected to this lead. TIN TTL/CMOS compatible transmitter Inputs. TOUT RIN ROUT ±15kV ESD Protected, RS-232 level (nominally ±5.5V) transmitter outputs. ±15kV ESD Protected, RS-232 compatible receiver inputs. TTL/CMOS level receiver outputs. ROUTB TTL/CMOS level, noninverting, always enabled receiver outputs. INVALID Active low output that indicates if no valid RS-232 levels are present on any receiver input. FORCEOFF Active low to shut down transmitters and on-chip power supply. This overrides any automatic circuitry and FORCEON (see Table 2). FORCEON EN SHDN NC Active high input to override automatic powerdown circuitry thereby keeping transmitters active. (FORCEOFF must be high). Active low receiver enable control. Active low input to shut down transmitters and on-board power supply, to place device in low power mode. No Connection 3 ISL4241E, ISL4243E Typical Operating Circuits ISL4241E +3.3V + C1 0.1µF C2 0.1µF T1IN ISL4243E +3.3V 0.1µF + 28 C1+ + 23 C129 C2+ + 30 C212 VCC V+ VT1 31 C4 0.1µF + T1OUT + C2 0.1µF C129 C2+ + 30 C2- C1+ 26 27 VCC + V+ 23 V- 12 T1 11 T2 31 T2OUT RS-232 LEVELS 7 T2OUT T3 10 19 RS-232 LEVELS 8 T3IN R1OUTB C4 0.1µF + T1OUT T2IN T3OUT 20 C3 0.1µF 6 T1IN 8 T3IN T3OUT 19 R2OUTB R2OUTB 18 1 R1OUT R1 17 15 R1IN R1 TTL/CMOS LOGIC LEVELS R2IN 5kΩ 17 14 R2IN RS-232 LEVELS R4 15 13 R3IN EN 5kΩ R5 R4IN R4 R5IN 5kΩ 13 5 R5OUT R5IN 22 5kΩ R5 FORCEON GND 24 VCC TO POWER CONTROL LOGIC 4 4 R4OUT 21 SHDN 5kΩ 14 5 R5OUT 3 R3 R4IN 5kΩ 5kΩ R3OUT 4 R4OUT 2 R2 R3IN 5kΩ R3 5kΩ R2OUT 3 R3OUT 1 R1OUT 2 R2 22 18 R1IN 5kΩ R2OUT VCC 28 C1 0.1µF 7 T3 10 + C3 0.1µF 6 T2 11 27 T2IN TTL/CMOS LOGIC LEVELS 0.1µF 26 21 FORCEOFF 20 INVALID GND 24 RS-232 LEVELS ISL4241E, ISL4243E Absolute Maximum Ratings Thermal Information VCC to Ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6V V+ to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 7V V- to Ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3V to -7V V+ to V- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14V Input Voltages TIN, FORCEOFF, FORCEON, EN, SHDN . . . . . . . . . -0.3V to 6V RIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±25V Output Voltages TOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±13.2V ROUT, INVALID. . . . . . . . . . . . . . . . . . . . . . . . -0.3V to VCC +0.3V Short Circuit Duration TOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . See Specification Table Thermal Resistance (Typical, Note 1) θJA (°C/W) 32 Ld QFN Package. . . . . . . . . . . . . . . . . . . . . . . . . 32 Maximum Junction Temperature (Plastic Package) . . . . . . . 150°C Maximum Storage Temperature Range . . . . . . . . . . . -65°C to 150°C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300°C Operating Conditions Temperature Range ISL424XEIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to 85°C CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTE: 1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech Brief TB379, and Tech Brief TB389. Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1µF; Unless Otherwise Specified. Typicals are at TA = 25°C Electrical Specifications PARAMETER TEST CONDITIONS TEMP (°C) MIN Full 2.7 - 5.5 V 25 - 3 300 nA Full - 50 300 nA 25 - 3 300 nA TYP MAX UNITS DC CHARACTERISTICS Operating Voltage Range Supply Current, Automatic Powerdown All RIN Open, FORCEON = GND, FORCEOFF = VCC (ISL4243E Only) Supply Current, Powerdown All RIN Open, FORCEOFF = SHDN = GND Supply Current, Automatic Powerdown Disabled All Outputs Unloaded, FORCEON = FORCEOFF = SHDN = VCC, VCC = 3.0V Full - 50 300 nA 25 - 0.3 1.0 mA Full - 0.3 1.5 mA LOGIC AND TRANSMITTER INPUTS AND RECEIVER OUTPUTS Input Logic Threshold Low TIN, FORCEON, FORCEOFF, EN, SHDN Full - - 0.8 V Input Logic Threshold High TIN, FORCEON, FORCEOFF, EN, SHDN, VCC = 3.6V Full 2.0 - - V Input Leakage Current TIN, FORCEON, FORCEOFF, EN, SHDN Full - ±0.01 ±1.0 µA Output Leakage Current FORCEOFF = GND (ISL4243E) or EN = VCC (ISL4241E) Full - ±0.05 ±10 µA 25 - 0.5 - V Output Voltage Low IOUT = 1.6mA Full - - 0.4 V Output Voltage High IOUT = -1.0mA Full - V Transmitter Input Hysteresis VCC -0.6 VCC -0.1 AUTOMATIC POWERDOWN (ISL4243E Only, FORCEON = GND, FORCEOFF = VCC) Receiver Input Thresholds to Enable Transmitters ISL4243E Powers Up (See Figure 7) Full -2.7 - 2.7 V Receiver Input Thresholds to Disable Transmitters ISL4243E Powers Down (See Figure 7) Full -0.3 - 0.3 V INVALID Output Voltage Low IOUT = 1.6mA Full - - 0.4 V INVALID Output Voltage High IOUT = -1.0mA Full VCC-0.6 - - V Full - 20 100 µs Receiver Threshold to Transmitters Enabled Delay (tWU) 5 ISL4241E, ISL4243E Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1µF; Unless Otherwise Specified. Typicals are at TA = 25°C (Continued) Electrical Specifications PARAMETER TEST CONDITIONS Receiver Positive or Negative Threshold to INVALID High Delay (tINVH) Receiver Positive or Negative Threshold to INVALID Low Delay (tINVL) TEMP (°C) MIN TYP MAX UNITS 25 - 0.5 1 µs Full - 0.9 1.5 µs 25 - 30 50 µs Full - 40 60 µs Full -25 - 25 V 1.0 0.6 V RECEIVER INPUTS Input Voltage Range Input Threshold Low VCC = 3.0V Full - Input Threshold High VCC = 3.6V Full 2.4 1.5 - V Input Hysteresis 25 - 0.5 - V Input Resistance Full 3 5 7 kΩ TRANSMITTER OUTPUTS Output Voltage Swing All Transmitter Outputs Loaded with 3kΩ to Ground Full ±5.0 ±5.4 - V Output Resistance VCC = V+ = V- = 0V, Transmitter Output = ±2V Full 300 10M - Ω Full - ±35 ±60 mA VOUT = ±12V, VCC = 0V or 3V to 5.5V, Automatic Powerdown or FORCEOFF = SHDN = GND Full - - ±25 µA Maximum Data Rate RL = 3kΩ, CL = 1000pF, One Transmitter Switching Full 250 500 - kbps Receiver Propagation Delay Receiver Input to Receiver Output, CL = 150pF 25 - 0.15 0.3 µs Full - 0.2 0.35 µs 25 - 0.3 0.5 µs Full - 0.35 0.55 µs Output Short-Circuit Current Output Leakage Current TIMING CHARACTERISTICS tPHL tPLH tPHL - tPLH, CL = 150pF Receiver Skew Transmitter Propagation Delay Transmitter Input to Transmitter Output, CL = 1000pF, RL = 3kΩ tPHL tPLH tPHL - tPLH (Note 2), RL = 3kΩ, CL = 1000pF Transmitter Skew Normal Operation, RL = 1kΩ to 0.5VCC, CL = 15pF Receiver Output Enable Time Normal Operation, RL = 1kΩ to 0.5VCC, CL = 15pF Receiver Output Disable Time Normal Operation, RL = 3kΩ, CL = 1000pF Transmitter Output Enable Time Normal Operation, RL = 3kΩ, CL = 1000pF Transmitter Output Disable Time 6 25 - 120 250 ns Full - 150 300 ns 25 - 0.75 1 µs Full - 0.85 1.1 µs 25 - 0.8 1 µs Full - 0.9 1.1 µs 25 - 50 200 ns Full - 100 250 ns 25 - 200 350 ns Full - 200 400 ns 25 - 350 500 ns Full - 400 600 ns 25 - 25 40 µs Full - 30 50 µs 25 - 2.5 4 µs Full - 2.7 4 µs ISL4241E, ISL4243E Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1µF; Unless Otherwise Specified. Typicals are at TA = 25°C (Continued) Electrical Specifications PARAMETER TEST CONDITIONS Transition Region Slew Rate VCC = 3V to 3.6V, RL = 3kΩ to 7kΩ, Measured From 3V to -3V or -3V to 3V TEMP (°C) MIN TYP MAX UNITS 25 4 9 30 V/µs CL = 150pF to 2500pF CL = 150pF to 1000pF Full 4 8 30 V/µs 25 6 11 30 V/µs Full 6 10 30 V/µs ESD PERFORMANCE RS-232 Pins (TOUT, RIN) All Other Pins Human Body Model 25 - ±15 - kV IEC61000-4-2 Contact Discharge 25 - ±8 - kV IEC61000-4-2 Air Gap Discharge 25 - ±15 - kV Human Body Model 25 - ±2 - kV NOTE: 2. Transmitter skew is measured at the transmitter zero crossing points. Detailed Description The ISL424XE operate from a single +2.7V to +5.5V supply, guarantee a 250kbps minimum data rate, require only four small external 0.1µF capacitors, feature low power consumption, and meet all ElA RS-232C and V.28 specifications even with VCC = 3.0V. The circuit is divided into three sections: The charge pump, the transmitters, and the receivers. Charge-Pump Intersil’s new ISL424XE devices utilize regulated on-chip dual charge pumps as voltage doublers, and voltage inverters to generate ±5.5V transmitter supplies from a VCC supply as low as 3.0V. This allows them to maintain RS-232 compliant output levels over the ±10% tolerance range of 3.3V powered systems. The efficient on-chip power supplies require only four small, external 0.1µF capacitors for the voltage doubler and inverter functions. The charge pumps operate discontinuously (i.e., they turn off as soon as the V+ and V- supplies are pumped up to the nominal values), resulting in significant power savings. conditions of VCC ≥ 3.3V, RL = 3kΩ, and CL = 250pF, one transmitter easily operates at 900kbps. Transmitter inputs float if left unconnected, and may cause ICC increases. Connect unused inputs to GND for the best performance. Receivers All the ISL424XE devices contain standard inverting receivers that three-state via the EN or FORCEOFF control lines. Additionally, the ISL424XE products include noninverting (monitor) receivers (denoted by the ROUTB label) that are always active, regardless of the state of any control lines. All the receivers convert RS-232 signals to CMOS output levels and accept inputs up to ±25V while presenting the required 3kΩ to 7kΩ input impedance (see Figure 1) even if the power is off (VCC = 0V). The receivers’ Schmitt trigger input stage uses hysteresis to increase noise immunity and decrease errors due to slow input signal transitions. VCC RXIN Transmitters -25V ≤ VRIN ≤ +25V The transmitters are proprietary, low dropout, inverting drivers that translate TTL/CMOS inputs to EIA/TIA-232 output levels. Coupled with the on-chip ±5.5V supplies, these transmitters deliver true RS-232 levels over a wide range of single supply system voltages. All transmitter outputs disable and assume a high impedance state when the device enters the powerdown mode (see Table 2). These outputs may be driven to ±12V when disabled. The devices guarantee a 250kbps data rate for full load conditions (3kΩ and 1000pF), VCC ≥ 3.0V, with one transmitter operating at full speed. Under more typical 7 RXOUT 5kΩ GND ≤ VROUT ≤ VCC GND FIGURE 1. INVERTING RECEIVER CONNECTIONS The ISL4241E inverting receivers disable only when EN is driven high. ISL4243E receivers disable during forced (manual) powerdown, but not during automatic powerdown (see Table 2). ISL424XE monitor receivers remain active even during manual powerdown, making them extremely useful for Ring Indicator monitoring. Standard receivers driving powered down peripherals must be disabled to prevent current flow through the peripheral’s protection diodes (see Figures 2 and 3). This renders them useless for wake up functions, but ISL4241E, ISL4243E powerdown mode). This is considerably less than the 5mA to 11mA current required by comparable 5V RS-232 devices, allowing users to reduce system power simply by switching to this new family. the corresponding monitor receiver can be dedicated to this task as shown in Figure 3. Low Power Operation These 3V devices require a nominal supply current of 0.3mA, even at VCC = 5.5V, during normal operation (not in TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE RS-232 SIGNAL PRESENT AT RECEIVER INPUT? SHDN OR FORCEOFF FORCEON EN TRANSMITTER RECEIVER ROUTB INVALID INPUT INPUT INPUT OUTPUTS OUTPUTS OUTPUTS OUTPUT MODE OF OPERATION ISL4241E N.A. L N.A. L High-Z Active Active N.A. Manual Powerdown N.A. L N.A. H High-Z High-Z Active N.A. Manual Powerdown w/Rcvr. Disabled N.A. H N.A. L Active Active Active N.A. Normal Operation N.A. H N.A. H Active High-Z Active N.A. Normal Operation w/Rcvr. Disabled NO H H N.A. Active Active Active L Normal Operation (Auto Powerdown Disabled) YES H L N.A. Active Active Active H Normal Operation (Auto Powerdown Enabled) NO H L N.A. High-Z Active Active L Powerdown Due to Auto Powerdown Logic YES L X N.A. High-Z High-Z Active H Manual Powerdown NO L X N.A. High-Z High-Z Active L Manual Powerdown ISL4243E VCC VCC for details. This micro-power mode makes the ISL424XE ideal for battery powered and portable applications. CURRENT FLOW VCC VCC VOUT = VCC TRANSITION DETECTOR Rx POWERED DOWN UART TO WAKE-UP LOGIC Tx GND SHDN = GND OLD RS-232 CHIP VCC R2OUTB RX FIGURE 2. POWER DRAIN THROUGH POWERED DOWN PERIPHERAL Powerdown Functionality The already low current requirement drops significantly when the device enters powerdown mode. In powerdown, supply current drops to 10nA, because the on-chip charge pump turns off (V+ collapses to VCC, V- collapses to GND), and the transmitter outputs three-state. Inverting receiver outputs disable only in manual powerdown; refer to Table 2 8 ISL424XE POWERED DOWN UART VOUT = HI-Z R2OUT TX R2IN T1IN T1OUT FORCEOFF = GND OR SHDN = GND, EN = VCC FIGURE 3. DISABLED RECEIVERS PREVENT POWER DRAIN Software Controlled (Manual) Powerdown Most devices in the ISL424XE family provide pins that allow the user to force the IC into the low power, standby state. ISL4241E, ISL4243E On the ISL4241E, the powerdown control is via a simple shutdown (SHDN) pin. Driving this pin high enables normal operation, while driving it low forces the IC into it’s powerdown state. Connect SHDN to VCC if the powerdown function isn’t needed. Note that all the receiver outputs remain enabled during shutdown (see Table 2). For the lowest power consumption during powerdown, the receivers should also be disabled by driving the EN input high (see next section, and Figures 2 and 3). The ISL4243E utilize a two pin approach where the FORCEON and FORCEOFF inputs determine the IC’s mode. For always enabled operation, FORCEON and FORCEOFF are both strapped high. To switch between active and powerdown modes, under logic or software control, only the FORCEOFF input need be driven. The FORCEON state isn’t critical, as FORCEOFF dominates over FORCEON. Nevertheless, if strictly manual control over powerdown is desired, the user must strap FORCEON high to disable the automatic powerdown circuitry. ISL4243E inverting (standard) receiver outputs also disable when the device is in manual powerdown, thereby eliminating the possible current path through a shutdown peripheral’s input protection diode (see Figures 2 and 3). Connecting FORCEOFF and FORCEON together disables the automatic powerdown feature, enabling them to function as a manual SHUTDOWN input (see Figure 4). FORCEOFF PWR MGT LOGIC FORCEON INVALID ISL4243E powering up. This gives the slow-to-wake peripheral circuit time to reestablish valid RS-232 output levels. POWER MANAGEMENT UNIT MASTER POWERDOWN LINE 0.1µF FORCEOFF 1MΩ FORCEON ISL4243E FIGURE 5. CIRCUIT TO PREVENT AUTO POWERDOWN FOR 100ms AFTER FORCED POWERUP INVALID Output (ISL4243E Only) The INVALID output always indicates whether or not a valid RS-232 signal (see Figure 6) is present at any of the receiver inputs (see Table 2), giving the user an easy way to determine when the interface block should power down. Invalid receiver levels occur whenever the driving peripheral’s outputs are shut off (powered down) or when the RS-232 interface cable is disconnected. In the case of a disconnected interface cable where all the receiver inputs are floating (but pulled to GND by the internal receiver pull down resistors), the INVALID logic detects the invalid levels and drives the output low. The power management logic then uses this indicator to power down the interface block. Reconnecting the cable restores valid levels at the receiver inputs, INVALID switches high, and the power management logic wakes up the interface block. INVALID can also be used to indicate the DTR or RING INDICATOR signal, as long as the other receiver inputs are floating, or driven to GND (as in the case of a powered down driver). VALID RS-232 LEVEL - ISL4243E IS ACTIVE 2.7V I/O UART INDETERMINATE - POWERDOWN MAY OR MAY NOT OCCUR CPU 0.3V INVALID LEVEL - POWERDOWN OCCURS AFTER 30µs -0.3V FIGURE 4. CONNECTIONS FOR MANUAL POWERDOWN WHEN NO VALID RECEIVER SIGNALS ARE PRESENT INDETERMINATE - POWERDOWN MAY OR MAY NOT OCCUR -2.7V VALID RS-232 LEVEL - ISL4243E IS ACTIVE With any of the above control schemes, the time required to exit powerdown, and resume transmission is only 100µs. A mouse, or other application, may need more time to wake up from shutdown. If automatic powerdown is being utilized, the RS-232 device will reenter powerdown if valid receiver levels aren’t reestablished within 30µs of the ISL4243E powering up. Figure 5 illustrates a circuit that keeps the ISL4243E from initiating automatic powerdown for 100ms after 9 FIGURE 6. DEFINITION OF VALID RS-232 RECEIVER LEVELS INVALID switches low after invalid levels have persisted on all of the receiver inputs for more than 30µs (see Figure 7). INVALID switches back high 1µs after detecting a valid RS-232 level on a receiver input. INVALID operates in all modes (forced or automatic powerdown, or forced on), so it is also useful for systems employing manual powerdown ISL4241E, ISL4243E circuitry. When automatic powerdown is utilized, INVALID = 0 indicates that the ISL4243E is in powerdown mode. INVALID } REGION RECEIVER INPUTS TRANSMITTER OUTPUTS INVALID OUTPUT VCC Power Supply Decoupling In most circumstances a 0.1µF bypass capacitor is adequate. In applications that are particularly sensitive to power supply noise, decouple VCC to ground with a capacitor of the same value as the charge-pump capacitor C1. Connect the bypass capacitor as close as possible to the IC. Transmitter Outputs when Exiting Powerdown tINVH tINVL 0 PWR UP AUTOPWDN V+ VCC 0 Figure 8 shows the response of two transmitter outputs when exiting powerdown mode. As they activate, the two transmitter outputs properly go to opposite RS-232 levels, with no glitching, ringing, nor undesirable transients. Each transmitter is loaded with 3kΩ in parallel with 2500pF. Note that the transmitters enable only when the magnitude of the supplies exceed approximately 3V. V- FIGURE 7. AUTOMATIC POWERDOWN AND INVALID TIMING DIAGRAMS 5V/DIV. FORCEOFF T1 Automatic Powerdown (ISL4243E Only) Even greater power savings is available by using the ISL4243E which features an automatic powerdown function. When no valid RS-232 voltages (see Figure 5) are sensed on any receiver input for 30µs, the charge pump and transmitters powerdown, thereby reducing supply current to 10nA. Invalid receiver levels occur whenever the driving peripheral’s outputs are shut off (powered down) or when the RS-232 interface cable is disconnected. The ISL4243E powers back up whenever it detects a valid RS-232 voltage level on any receiver input. This automatic powerdown feature provides additional system power savings without changes to the existing operating system. 2V/DIV. T2 VCC = +3.3V C1 - C4 = 0.1µF TIME (20µs/DIV.) FIGURE 8. TRANSMITTER OUTPUTS WHEN EXITING POWERDOWN Automatic powerdown operates when the FORCEON input is low, and the FORCEOFF input is high. Tying FORCEON high disables automatic powerdown, but manual powerdown is always available via the overriding FORCEOFF input. Table 2 summarizes the automatic powerdown functionality. ISL424XE transmitter outputs meet RS-562 levels (±3.7V), at the full data rate, with VCC as low as 2.7V. RS-562 levels typically ensure inter operability with RS-232 devices. The time to recover from automatic powerdown mode is typically 100µs. High Data Rates Capacitor Selection The charge pumps require 0.1µF, or greater, capacitors for proper operation. Increasing the capacitor values (by a factor of 2) reduces ripple on the transmitter outputs and slightly reduces power consumption. When using minimum required capacitor values, make sure that capacitor values do not degrade excessively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance (ESR) usually rises at low temperatures and it influences the amount of ripple on V+ and V-. 10 Operation Down to 2.7V The ISL424XE maintain the RS-232 ±5V minimum transmitter output voltages even at high data rates. Figure 9 details a transmitter loopback test circuit, and Figure 10 illustrates the loopback test result at 120kbps. For this test, all transmitters were simultaneously driving RS-232 loads in parallel with 1000pF, at 120kbps. Figure 11 shows the loopback results for a single transmitter driving 1000pF and an RS-232 load at 250kbps. The static transmitters were also loaded with an RS-232 receiver. ISL4241E, ISL4243E Interconnection with 3V and 5V Logic VCC + 0.1µF + VCC C1+ V+ C1 C1- + C3 ISL424XE + V- C2+ C2 C4 + C2TIN TOUT RIN ROUT FORCEON VCC 1000pF 5k FORCEOFF or SHDN The ISL424XE directly interface with 5V CMOS and TTL logic families. Nevertheless, with the ISL424XE at 3.3V, and the logic supply at 5V, AC, HC, and CD4000 outputs can drive ISL424XE inputs, but ISL424XE outputs do not reach the minimum VIH for these logic families. See Table 3 for more information. TABLE 3. LOGIC FAMILY COMPATIBILITY WITH VARIOUS SUPPLY VOLTAGES SYSTEM POWER-SUPPLY VOLTAGE (V) VCC SUPPLY VOLTAGE (V) 3.3 3.3 5 5 5 3.3 FIGURE 9. TRANSMITTER LOOPBACK TEST CIRCUIT 5V/DIV. T1IN COMPATIBILITY Compatible with all CMOS families. Compatible with all TTL and CMOS logic families. Compatible with ACT and HCT CMOS, and with TTL. ISL424XE outputs are incompatible with AC, HC, and CD4000 CMOS inputs. ±15kV ESD Protection T1OUT R1OUT VCC = +3.3V C1 - C4 = 0.1µF 5µs/DIV. FIGURE 10. LOOPBACK TEST AT 120kbps All pins on ISL424XE devices include ESD protection structures, but the RS-232 pins (transmitter outputs and receiver inputs) incorporate advanced structures which allow them to survive ESD events up to ±15kV. The RS-232 pins are particularly vulnerable to ESD damage because they typically connect to an exposed port on the exterior of the finished product. Simply touching the port pins, or connecting a cable, can cause an ESD event that might destroy unprotected ICs. These new ESD structures protect the device whether or not it is powered up, protect without allowing any latchup mechanism to activate, and don’t interfere with RS-232 signals as large as ±25V. Human Body Model (HBM) Testing 5V/DIV. As the name implies, this test method emulates the ESD event delivered to an IC during human handling. The tester delivers the charge through a 1.5kΩ current limiting resistor, making the test less severe than the IEC61000 test which utilizes a 330Ω limiting resistor. The HBM method determines an ICs ability to withstand the ESD transients typically present during handling and manufacturing. Due to the random nature of these events, each pin is tested with respect to all other pins. The RS-232 pins on “E” family devices can withstand HBM ESD events to ±15kV. T1IN T1OUT R1OUT IEC61000-4-2 Testing VCC = +3.3V C1 - C4 = 0.1µF 2µs/DIV. FIGURE 11. LOOPBACK TEST AT 250kbps 11 The IEC61000 test method applies to finished equipment, rather than to an individual IC. Therefore, the pins most likely to suffer an ESD event are those that are exposed to the outside world (the RS-232 pins in this case), and the IC is tested in its typical application configuration (power applied) rather than testing each pin-to-pin combination. The lower current limiting resistor coupled with the larger charge ISL4241E, ISL4243E storage capacitor yields a test that is much more severe than the HBM test. The extra ESD protection built into this device’s RS-232 pins allows the design of equipment meeting level 4 criteria without the need for additional board level protection on the RS-232 port. AIR-GAP DISCHARGE TEST METHOD For this test method, a charged probe tip moves toward the IC pin until the voltage arcs to it. The current waveform delivered to the IC pin depends on approach speed, humidity, temperature, etc., so it is difficult to obtain Typical Performance Curves repeatable results. The “E” device RS-232 pins withstand ±15kV air-gap discharges. CONTACT DISCHARGE TEST METHOD During the contact discharge test, the probe contacts the tested pin before the probe tip is energized, thereby eliminating the variables associated with the air-gap discharge. The result is a more repeatable and predictable test, but equipment limits prevent testing devices at voltages higher than ±8kV. All “E” family devices survive ±8kV contact discharges on the RS-232 pins. VCC = 3.3V, TA = 25oC TRANSMITTER OUTPUT VOLTAGE (V) 6 25 VOUT+ 4 SLEW RATE (V/µs) 20 2 1 TRANSMITTER AT 250kbps OTHER TRANSMITTERS AT 30kbps 0 -2 15 -SLEW +SLEW 10 VOUT - -4 -6 0 1000 2000 3000 4000 5 5000 0 1000 FIGURE 12. TRANSMITTER OUTPUT VOLTAGE vs LOAD CAPACITANCE 3000 4000 5000 FIGURE 13. SLEW RATE vs LOAD CAPACITANCE 45 3.5 40 3.0 250kbps SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 2000 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF) 35 30 120kbps 25 20 20kbps 15 NO LOAD ALL OUTPUTS STATIC 2.5 2.0 1.5 1.0 0.5 10 0 2000 1000 3000 4000 5000 0 2.5 3.0 LOAD CAPACITANCE (pF) FIGURE 14. SUPPLY CURRENT vs LOAD CAPACITANCE WHEN TRANSMITTING DATA GND ISL424XE: 464 12 4.5 5.0 5.5 FIGURE 15. SUPPLY CURRENT vs SUPPLY VOLTAGE PROCESS: Si Gate CMOS TRANSISTOR COUNT: 4.0 SUPPLY VOLTAGE (V) Die Characteristics SUBSTRATE POTENTIAL (POWERED UP): 3.5 6.0 ISL4241E, ISL4243E Quad Flat No-Lead Plastic Package (QFN) Micro Lead Frame Plastic Package (MLFP) L32.5x5 32 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE (COMPLIANT TO JEDEC MO-220VHHD-2 ISSUE C MILLIMETERS SYMBOL MIN NOMINAL MAX NOTES A 0.80 0.90 1.00 - A1 - - 0.05 - A2 - - 1.00 9 A3 b 0.20 REF 0.18 D 0.30 5,8 5.00 BSC D1 D2 0.23 9 - 4.75 BSC 2.95 3.10 9 3.25 7,8 E 5.00 BSC - E1 4.75 BSC 9 E2 2.95 e 3.10 3.25 7,8 0.50 BSC - k 0.25 - - - L 0.30 0.40 0.50 8 L1 - - 0.15 10 N Nd 32 2 8 3 Ne 8 8 3 P - - 0.60 9 θ - - 12 9 Rev. 1 10/02 NOTES: 1. Dimensioning and tolerancing conform to ASME Y14.5-1994. 2. N is the number of terminals. 3. Nd and Ne refer to the number of terminals on each D and E. 4. All dimensions are in millimeters. Angles are in degrees. 5. Dimension b applies to the metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 6. The configuration of the pin #1 identifier is optional, but must be located within the zone indicated. The pin #1 identifier may be either a mold or mark feature. 7. Dimensions D2 and E2 are for the exposed pads which provide improved electrical and thermal performance. 8. Nominal dimensions are provided to assist with PCB Land Pattern Design efforts, see Intersil Technical Brief TB389. 9. Features and dimensions A2, A3, D1, E1, P & θ are present when Anvil singulation method is used and not present for saw singulation. 10. Depending on the method of lead termination at the edge of the package, a maximum 0.15mm pull back (L1) maybe present. L minus L1 to be equal to or greater than 0.3mm. All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com 13