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ISL4241E, ISL4243E
Data Sheet May 2004 FN8037.4
QFN Packaged, 15kV ESD Protected, +2.7V to +5.5V, 10Nanoamp, 250kbps, RS-232 Transmitters/Receivers
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.
Features
* Pb-free Available as an Option * 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 0.1F 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 ISL4241E ISL4243E NO. OF MONITOR Rx. NO. OF NO. OF QFN PKG. (ROUTB) Tx. Rx. AVAILABLE? 3 3 5 5 YES YES 2 1 DATA RATE (kbps) 250 250 Rx. ENABLE FUNCTION? YES NO READY OUTPUT? NO NO MANUAL POWERDOWN? YES YES AUTOMATIC POWERDOWN FUNCTION? NO 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 (c) Intersil Americas Inc. 2004. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
ISL4241E, ISL4243E Ordering Information
PART NO. ISL4241EIR ISL4241EIRZ (See Note) ISL4241EIR-T ISL4241EIRZ-T (See Note) ISL4243EIR ISL4243EIRZ (See Note) ISL4243EIR-T ISL4243EIRZ-T (See Note) TEMP. RANGE (C) -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 PACKAGE 32 Ld QFN 32 Ld QFN (Pb-free) Tape & Reel Tape & Reel (Pb-free) 32 Ld QFN 32 Ld QFN (Pb-free) Tape & Reel Tape & Reel (Pb-free) PKG. DWG. # L32.5x5 L32.5x5 L32.5x5 L32.5x5 L32.5x5 L32.5x5 L32.5x5 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
ISL4241E (QFN) TOP VIEW
VCC C2+ C1+ C2NC C2NC V+ NC V-
ISL4243E (QFN) TOP VIEW
VCC 26 C2+ C1+ V+ NC 25 24 23 22 21 20 19 18 17 9 NC 10 T3IN 11 T2IN 12 T1IN 13 R5OUT 14 R4OUT 15 R3OUT 16 NC GND C1FORCEON FORCEOFF INVALID R2OUTB R1OUT R2OUT
V-
32 R1IN R2IN R3IN R4IN R5IN T1OUT T2OUT T3OUT 1 2 3 4 5 6 7 8 9 NC
31
30
29
28
27
26
25 24 23 22 21 20 19 18 17 GND C1EN SHDN R1OUTB R2OUTB R1OUT R2OUT R1IN R2IN R3IN R4IN R5IN T1OUT T2OUT T3OUT 1 2 3 4 5 6 7 8
32
31
30
29
28
27
10 T3IN
11 T2IN
12 T1IN
13 R5OUT
14 R4OUT
15 R3OUT
16 NC
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ISL4241E, ISL4243E Pin Descriptions
PIN VCC V+ VGND C1+ C1C2+ C2TIN TOUT RIN ROUT ROUTB INVALID System power supply input (2.7V to 5.5V). Internally generated positive transmitter supply (+5.5V). Internally generated negative transmitter supply (-5.5V). Ground connection. External capacitor (voltage doubler) is connected to this lead. External capacitor (voltage doubler) is connected to this lead. External capacitor (voltage inverter) is connected to this lead. External capacitor (voltage inverter) is connected to this lead. TTL/CMOS compatible transmitter Inputs. 15kV ESD Protected, RS-232 level (nominally 5.5V) transmitter outputs. 15kV ESD Protected, RS-232 compatible receiver inputs. TTL/CMOS level receiver outputs. TTL/CMOS level, noninverting, always enabled receiver outputs. Active low output that indicates if no valid RS-232 levels are present on any receiver input. FUNCTION
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
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ISL4241E, ISL4243E Typical Operating Circuits
ISL4241E
+3.3V + +3.3V 0.1F 26 VCC V+ 27 + C3 0.1F C4 0.1F + T1OUT 7 T2OUT 8 T3OUT RS-232 LEVELS 11 T2IN 10 T3IN 19 R2OUTB 18 TTL/CMOS LOGIC LEVELS R1OUT R1 17 R2OUT R2 15 R3OUT R3 14 R4OUT R4 13 R5OUT 22 21 SHDN GND 24 VCC TO POWER CONTROL LOGIC 21 FORCEOFF 20 INVALID GND 24 EN R5 5k 5k 5 R5IN R5OUT 22 R5 FORCEON 5k 13 5k 4 R4IN R4OUT R4 5k 5 R5IN 14 5k 3 R3IN RS-232 LEVELS 15 R3OUT R3 5k 4 R4IN 5k 2 R2IN 1 R1IN TTL/CMOS LOGIC LEVELS R2OUT R2 5k 3 R3IN RS-232 LEVELS 18 R1OUT R1 17 5k 2 R2IN 1 R1IN T3 8 T3OUT T2 7 T2OUT C1 0.1F C2 0.1F + 23 +
ISL4243E
0.1F 28 C1+
26 VCC 27 V+ 31 + C3 0.1F
C1 0.1F C2 0.1F T1IN T2IN
28 C1+ + 23 C129 C2+ + 30 C212 11 10
VT1 T2 T3
31
C129 C2+ + 30 C212 T1
V-
6 T1IN
C4 0.1F +
6 T1OUT RS-232 LEVELS
T3IN 20 R1OUTB 19 R2OUTB
VCC
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ISL4241E, ISL4243E
Absolute Maximum Ratings
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 Information
Thermal Resistance (Typical, Note 1)
JA (C/W)
32 Ld QFN Package. . . . . . . . . . . . . . . . . . . . . . . . . 32 Maximum Junction Temperature (Plastic Package) . . . . . . . 150C Maximum Storage Temperature Range . . . . . . . . . . . -65C to 150C Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300C
Operating Conditions
Temperature Range ISL424XEIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40C to 85C
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. JA 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.
Electrical Specifications
Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1F; Unless Otherwise Specified. Typicals are at TA = 25C TEST CONDITIONS TEMP (C) MIN TYP MAX UNITS
PARAMETER DC CHARACTERISTICS Operating Voltage Range Supply Current, Automatic Powerdown Supply Current, Powerdown
Full All RIN Open, FORCEON = GND, FORCEOFF = VCC (ISL4243E Only) All RIN Open, FORCEOFF = SHDN = GND 25 Full 25 Full
2.7 -
3 50 3 50 0.3 0.3
5.5 300 300 300 300 1.0 1.5
V nA nA nA nA mA mA
Supply Current, Automatic Powerdown Disabled
All Outputs Unloaded, FORCEON = FORCEOFF = SHDN = VCC, VCC = 3.0V
25 Full
LOGIC AND TRANSMITTER INPUTS AND RECEIVER OUTPUTS Input Logic Threshold Low Input Logic Threshold High Input Leakage Current Output Leakage Current Transmitter Input Hysteresis Output Voltage Low Output Voltage High IOUT = 1.6mA IOUT = -1.0mA TIN, FORCEON, FORCEOFF, EN, SHDN TIN, FORCEON, FORCEOFF, EN, SHDN, VCC = 3.6V TIN, FORCEON, FORCEOFF, EN, SHDN FORCEOFF = GND (ISL4243E) or EN = VCC (ISL4241E) Full Full Full Full 25 Full Full 2.0 0.01 0.05 0.5 0.8 1.0 10 0.4 V V A A V V V
VCC -0.6 VCC -0.1
AUTOMATIC POWERDOWN (ISL4243E Only, FORCEON = GND, FORCEOFF = VCC) Receiver Input Thresholds to Enable Transmitters Receiver Input Thresholds to Disable Transmitters INVALID Output Voltage Low INVALID Output Voltage High Receiver Threshold to Transmitters Enabled Delay (tWU) ISL4243E Powers Up (See Figure 7) ISL4243E Powers Down (See Figure 7) IOUT = 1.6mA IOUT = -1.0mA Full Full Full Full Full -2.7 -0.3 VCC-0.6 20 2.7 0.3 0.4 100 V V V V s
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ISL4241E, ISL4243E
Electrical Specifications
Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1F; Unless Otherwise Specified. Typicals are at TA = 25C (Continued) TEST CONDITIONS TEMP (C) 25 Full 25 Full MIN TYP 0.5 0.9 30 40 MAX 1 1.5 50 60 UNITS s s s s
PARAMETER Receiver Positive or Negative Threshold to INVALID High Delay (tINVH) Receiver Positive or Negative Threshold to INVALID Low Delay (tINVL) RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TRANSMITTER OUTPUTS Output Voltage Swing Output Resistance Output Short-Circuit Current Output Leakage Current TIMING CHARACTERISTICS Maximum Data Rate Receiver Propagation Delay VCC = 3.0V VCC = 3.6V
Full Full Full 25 Full
-25 2.4 3
1.0 1.5 0.5 5
25 0.6 7
V V V V k
All Transmitter Outputs Loaded with 3k to Ground VCC = V+ = V- = 0V, Transmitter Output = 2V VOUT = 12V, VCC = 0V or 3V to 5.5V, Automatic Powerdown or FORCEOFF = SHDN = GND
Full Full Full Full
5.0 300 -
5.4 10M 35 -
60 25
V mA A
RL = 3k, CL = 1000pF, One Transmitter Switching Receiver Input to Receiver Output, CL = 150pF tPHL
Full 25 Full
250 -
500 0.15 0.2 0.3 0.35 120 150 0.75 0.85 0.8 0.9 50 100 200 200 350 400 25 30 2.5 2.7
0.3 0.35 0.5 0.55 250 300 1 1.1 1 1.1 200 250 350 400 500 600 40 50 4 4
kbps s s s s ns ns s s s s ns ns ns ns ns ns s s s s
tPLH
25 Full
Receiver Skew
tPHL - tPLH, CL = 150pF
25 Full
Transmitter Propagation Delay
Transmitter Input to Transmitter Output, CL = 1000pF, RL = 3k
tPHL
25 Full
tPLH
25 Full
Transmitter Skew
tPHL - tPLH (Note 2), RL = 3k, CL = 1000pF
25 Full
Receiver Output Enable Time
Normal Operation, RL = 1k to 0.5VCC, CL = 15pF
25 Full
Receiver Output Disable Time
Normal Operation, RL = 1k to 0.5VCC, CL = 15pF
25 Full
Transmitter Output Enable Time
Normal Operation, RL = 3k, CL = 1000pF
25 Full
Transmitter Output Disable Time
Normal Operation, RL = 3k, CL = 1000pF
25 Full
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ISL4241E, ISL4243E
Electrical Specifications
Test Conditions: VCC = 3V to 5.5V, C1 - C4 = 0.1F; Unless Otherwise Specified. Typicals are at TA = 25C (Continued) TEST CONDITIONS VCC = 3V to 3.6V, RL = 3k to 7k, Measured From 3V to -3V or -3V to 3V CL = 150pF to 2500pF CL = 150pF to 1000pF ESD PERFORMANCE RS-232 Pins (TOUT, RIN) Human Body Model IEC61000-4-2 Contact Discharge IEC61000-4-2 Air Gap Discharge All Other Pins NOTE: 2. Transmitter skew is measured at the transmitter zero crossing points. Human Body Model 25 25 25 25 15 8 15 2 kV kV kV kV TEMP (C) 25 Full 25 Full MIN 4 4 6 6 TYP 9 8 11 10 MAX 30 30 30 30 UNITS V/s V/s V/s V/s
PARAMETER Transition Region Slew Rate
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 0.1F 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.
conditions of VCC 3.3V, RL = 3k, 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 3k to 7k 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 -25V VRIN +25V GND 5k RXOUT GND VROUT VCC
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 0.1F 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.
Transmitters
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 (3k and 1000pF), VCC 3.0V, with one transmitter operating at full speed. Under more typical
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
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ISL4241E, ISL4243E
the corresponding monitor receiver can be dedicated to this task as shown in Figure 3. 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.
Low Power Operation
These 3V devices require a nominal supply current of 0.3mA, even at VCC = 5.5V, during normal operation (not in
RS-232 SIGNAL PRESENT AT RECEIVER INPUT? ISL4241E N.A. N.A. N.A. N.A. ISL4243E NO YES NO YES NO H H H L L H L L X X N.A. N.A. N.A. N.A. N.A. Active Active High-Z High-Z High-Z Active Active Active L L H H N.A. N.A. N.A. N.A. L H L H High-Z High-Z Active Active Active
TABLE 2. POWERDOWN AND ENABLE LOGIC TRUTH TABLE
SHDN OR FORCEOFF FORCEON EN TRANSMITTER RECEIVER ROUTB INVALID INPUT INPUT INPUT OUTPUTS OUTPUTS OUTPUTS OUTPUT
MODE OF OPERATION
Active Active Active Active
N.A. N.A. N.A. N.A.
Manual Powerdown Manual Powerdown w/Rcvr. Disabled Normal Operation Normal Operation w/Rcvr. Disabled
High-Z Active High-Z
Active Active Active Active Active
L H L H L
Normal Operation (Auto Powerdown Disabled) Normal Operation (Auto Powerdown Enabled) Powerdown Due to Auto Powerdown Logic Manual Powerdown Manual Powerdown
High-Z High-Z
VCC
VCC CURRENT FLOW VOUT = VCC
for details. This micro-power mode makes the ISL424XE ideal for battery powered and portable applications.
VCC
VCC
Rx POWERED DOWN UART Tx GND SHDN = GND OLD RS-232 CHIP
TRANSITION DETECTOR TO WAKE-UP LOGIC VCC R2OUTB RX VOUT = HI-Z R2OUT TX T1IN T1OUT FORCEOFF = GND OR SHDN = GND, EN = VCC R2IN ISL424XE
FIGURE 2. POWER DRAIN THROUGH POWERED DOWN PERIPHERAL
POWERED DOWN UART
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
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.
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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
powering up. This gives the slow-to-wake peripheral circuit time to reestablish valid RS-232 output levels.
POWER MANAGEMENT UNIT
MASTER POWERDOWN LINE 0.1F 1M
FORCEOFF
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
INVALID ISL4243E
I/O UART CPU 0.3V
INDETERMINATE - POWERDOWN MAY OR MAY NOT OCCUR
INVALID LEVEL - POWERDOWN OCCURS AFTER 30s -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 100s. 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 30s of the ISL4243E powering up. Figure 5 illustrates a circuit that keeps the ISL4243E from initiating automatic powerdown for 100ms after
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 30s (see Figure 7). INVALID switches back high 1s 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
9
ISL4241E, ISL4243E
circuitry. When automatic powerdown is utilized, INVALID = 0 indicates that the ISL4243E is in powerdown mode.
Power Supply Decoupling
In most circumstances a 0.1F 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.
RECEIVER INPUTS
INVALID } REGION
TRANSMITTER OUTPUTS VCC 0 AUTOPWDN V+ VCC 0 V-
Transmitter Outputs when Exiting Powerdown
tINVL tINVH PWR UP
INVALID OUTPUT
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 3k in parallel with 2500pF. Note that the transmitters enable only when the magnitude of the supplies exceed approximately 3V.
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 30s, 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. 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. The time to recover from automatic powerdown mode is typically 100s.
2V/DIV.
T2 VCC = +3.3V C1 - C4 = 0.1F TIME (20s/DIV.)
FIGURE 8. TRANSMITTER OUTPUTS WHEN EXITING POWERDOWN
Operation Down to 2.7V
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.
High Data Rates
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.
Capacitor Selection
The charge pumps require 0.1F, 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
ISL4241E, ISL4243E
VCC 0.1F
Interconnection with 3V and 5V Logic
+
+ C1
C1+ C1-
VCC
V+
+ C3
ISL424XE + C2 C2TIN ROUT FORCEON VCC 5k TOUT RIN 1000pF C2+ VC4 +
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) 3.3 5 5 VCC SUPPLY VOLTAGE (V) 3.3 5 3.3
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.
FORCEOFF or SHDN
FIGURE 9. TRANSMITTER LOOPBACK TEST CIRCUIT
5V/DIV. T1IN
15kV ESD Protection
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.
T1OUT
R1OUT VCC = +3.3V C1 - C4 = 0.1F 5s/DIV.
FIGURE 10. LOOPBACK TEST AT 120kbps
Human Body Model (HBM) Testing
5V/DIV. T1IN
T1OUT
R1OUT VCC = +3.3V C1 - C4 = 0.1F 2s/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 1.5k current limiting resistor, making the test less severe than the IEC61000 test which utilizes a 330 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.
IEC61000-4-2 Testing
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
FIGURE 11. LOOPBACK TEST AT 250kbps
11
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 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.
Typical Performance Curves
6 TRANSMITTER OUTPUT VOLTAGE (V) 4 2 1 TRANSMITTER AT 250kbps OTHER TRANSMITTERS AT 30kbps 0 -2 -4 -6
VCC = 3.3V, TA = 25oC
25 VOUT+ 20 SLEW RATE (V/s)
15 -SLEW +SLEW 10
VOUT 5
0
1000
2000
3000
4000
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
FIGURE 12. TRANSMITTER OUTPUT VOLTAGE vs LOAD CAPACITANCE
45 40 SUPPLY CURRENT (mA) 35 30 120kbps 25 20 20kbps 15 10 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF) SUPPLY CURRENT (mA) 250kbps
FIGURE 13. SLEW RATE vs LOAD CAPACITANCE
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 2.5
NO LOAD ALL OUTPUTS STATIC
3.0
3.5
4.0
4.5
5.0
5.5
6.0
SUPPLY VOLTAGE (V)
FIGURE 14. SUPPLY CURRENT vs LOAD CAPACITANCE WHEN TRANSMITTING DATA
FIGURE 15. SUPPLY CURRENT vs SUPPLY VOLTAGE
Die Characteristics
SUBSTRATE POTENTIAL (POWERED UP): GND TRANSISTOR COUNT: ISL424XE: 464 12 PROCESS: Si Gate CMOS
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 A A1 A2 A3 b D D1 D2 E E1 E2 e k L L1 N Nd Ne P 8 0.25 0.30 2.95 2.95 0.18 MIN 0.80 NOMINAL 0.90 0.20 REF 0.23 5.00 BSC 4.75 BSC 3.10 5.00 BSC 4.75 BSC 3.10 0.50 BSC 0.40 32 8 8 0.60 12 0.50 0.15 3.25 3.25 0.30 MAX 1.00 0.05 1.00 NOTES 9 9 5,8 9 7,8 9 7,8 8 10 2 3 3 9 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 & 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

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