LTC1323 Single 5V AppleTalk Transceiver ® U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®1323 is a multi-protocol line transceiver designed to operate on AppleTalk or EIA562-compatible singleended networks while operating from a single 5V supply. There are two versions of the LTC1323 available: a 16-pin version designed to connect to an AppleTalk network, and a 24-pin version which also includes the additional single-ended drivers and receivers necessary to create an Apple-compatible serial port. An on-board charge pump generates a – 5V supply which can be used to power external devices. Additionally, the 24-pin LTC1323 features a micropower keep-alive mode during which one of the single-ended receivers is kept active to monitor external wake-up signals. The LTC1323 draws only 2.4mA quiescent current when active, 65µA in receiver keepalive mode, and 0.5µA in shutdown, making it ideal for use in battery-powered systems. Single Chip Provides Complete LocalTalk®/AppleTalk Port Operates From a Single 5V Supply ESD Protection to ±10kV on Receiver Inputs and Driver Outputs Low Power: ICC = 2.4mA Typ Shutdown Pin Reduces ICC to 0.5µA Typ Receiver Keep-Alive Function: ICC = 65µA Typ Differential Driver Drives Either Differential AppleTalk or Single-Ended EIA562 Loads Drivers Maintain High Impedance in Three-State or with Power Off Thermal Shutdown Protection Drivers are Short-Circuit Protected UO APPLICATI ■ ■ ■ S The differential driver can drive either differential AppleTalk loads or conventional single-ended loads. The driver outputs three-state when disabled, during shutdown, in receiver keep-alive mode, or when the power is off. The driver outputs will maintain high impedance even with output common-mode voltages beyond the power supply rails. Both the driver outputs and receiver inputs are protected against ESD damage to ±10kV. LocalTalk Peripherals Notebook/Palmtop Computers Battery-Powered Systems , LTC and LT are registered trademarks of Linear Technology Corporation. AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc. UO TYPICAL APPLICATI LTC1323 0.33µF 2 CHARGE PUMP CPEN 3 TXD 4 5V 24 1 21 DX TXI 5 20 TXD – TXDEN 6 19 TXD + SHDN 7 18 TXO RXEN 8 17 RXI RXO 9 RXO 10 RX RX 12 16 RXI 15 RXD – 14 RXD + RXDO 11 RX 1µF 23 22 DX + 5Ω TO 10Ω 5Ω TO 10Ω EMI FILTER = 0.33µF 1µF 100pF + EMI FILTER EMI FILTER EMI FILTER EMI FILTER 8 7 6 EMI FILTER 5 4 3 EMI FILTER 2 1 EMI FILTER 13 LTC1323 • TA01 1 LTC1323 W W W AXI U U ABSOLUTE RATI GS Supply Voltage (VCC) ................................................ 7V Input Voltage Logic Inputs .............................. – 0.3V to VCC + 0.3V Receiver Inputs ................................................ ±15V Driver Output Voltage (Forced) ............................. ±15V Driver Short-Circuit Duration .......................... Indefinite Operating Temperature Range .................... 0°C to 70°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO TOP VIEW C1+ 1 28 VCC C2 – 2 27 C2+ CPEN 3 26 C2 – TXD 4 25 NC TXI 5 24 NC TXDEN 6 23 VEE ORDER PART NUMBER LTC1323CG 22 TXD– SHDN 7 21 TXD+ RXEN 8 RXO 9 20 TXO RXO 10 19 RXI RXDO 11 18 RXI NC 12 17 RXD– NC 13 RXD+ 16 GND 14 1 24 VCC 23 C2+ CPEN 3 22 C2 – TXD 4 21 VEE TXI 5 20 TXD – TXDEN 6 19 TXD+ SHDN 7 18 TXO RXEN 8 17 RXI RXO 9 16 RXI RXO 10 15 RXD – RXDO 11 14 RXD+ GND 12 13 PGND SW PACKAGE 24-LEAD PLASTIC SO WIDE TJMAX = 125°C, θJA = 85°C/W Consult factory for Industrial and Military grade parts. 2 16 VCC C1– 2 15 C2+ TXD 3 14 C2 – TXDEN 4 13 VEE SHDN 5 12 TXD – RXEN 6 11 TXD + RXDO 7 10 RXD – 9 TJMAX = 125°C, θJA = 85°C/W TJMAX = 150°C, θJA = 96°C/W C1 – 2 LTC1323CS 1 S PACKAGE 16-LEAD PLASTIC SO 15 PGND TOP VIEW TOP VIEW C1+ GND 8 G PACKAGE 28-LEAD PLASTIC SSOP C1+ ORDER PART NUMBER ORDER PART NUMBER LTC1323CSW RXD+ LTC1323 ELECTRICAL CHARACTERISTICS SYMBOL VCC = 5V ±10%, TA = 0°C to 70°C (Notes 2, 3) PARAMETER CONDITIONS Normal Operation Supply Current No Load, SHDN = 0V, CPEN = 0V, TXDEN = 0V, RXEN = 0V Receiver Keep-Alive Supply Current MIN TYP MAX UNITS ● 2.4 4 mA No Load, SHDN = 0V, CPEN = VCC, TXDEN = 0V, RXEN = 0V ● 65 100 µA Shutdown Supply Current No Load, SHDN = VCC, CPEN = X, TXDEN = X, RXEN = 0V ● 0.5 10 µA VEE Negative Supply Output Voltage ILOAD ≤ 10mA (Note 4), VCC = 5V, RL = 100Ω (Figure 1), TXI = VCC, RTXO = 3k (Figure 5) ● –5 – 4.5 V fOSC Charge Pump Oscillator Frequency Supplies ICC – 5.5 200 kHz Differential Driver VOD Differential Output Voltage No Load RL = 100Ω (Figure 1) ∆VOD Change in Magnitude of Differential Output Voltage RL = 100Ω (Figure 1) ● ● ±8 ±2 V 0.2 V 3 V Differential Driver VOC Differential Common-Mode Output Voltage RL = 100Ω VOS Single-Ended Output Voltage No Load RL = 3k to GND ● ● VCMR Common-Mode Range SHDN = VCC or CPEN = VCC or Power Off ● ISS Short-Circuit Current – 5V ≤ VO ≤ 5V ● IOZ Three-State Output Current SHDN = VCC or CPEN = VCC or Power Off, – 10V ≤ VO ≤ 10V ● ±4.0 ±3.7 35 V V ±10 V 120 500 mA ±2 ±200 µA Single-Ended Driver (Note 5) ±4.5 ±3.7 VOS Single-Ended Output Voltage No Load RL = 3k to GND ● ● VCMR Common-Mode Range SHDN = VCC or CPEN = VCC or TXDEN = VCC or Power Off ● ISS Short-Circuit Current – 5V ≤ VO ≤ 5V ● IOZ Three-State Output Current SHDN = VCC or CPEN = VCC or TXDEN = VCC or Power Off, – 10V ≤ VO ≤ 10V ● Input Resistance – 7V ≤ VIN ≤ 7V ● 12 Differential Receiver Threshold Voltage – 7V ≤ VCM ≤ 7V ● – 200 Differential Receiver Input Hysteresis – 7V ≤ VCM ≤ 7V ● Single-Ended Input, Low Voltage (Note 5) ● Single-Ended Input, High Voltage (Note 5) ● 2 V VOH Output High Voltage IO = – 4mA ● 3.5 V VOL Output Low Voltage IO = 4mA ● ISS Output Short-Circuit Current – 5V ≤ VO ≤ 5V ● IOZ Output Three-State Current – 5V ≤ VO ≤ 5V, RXEN = VCC ● 35 V V ±10 V 220 500 mA ±2 ±200 µA 200 mV Receivers RIN kΩ 70 mV 0.8 7 ±2 V 0.4 V 85 mA ±100 µA 3 LTC1323 ELECTRICAL CHARACTERISTICS SYMBOL VCC = 5V ±10%, TA = 0°C to 70°C (Notes 2 and 3) PARAMETER CONDITIONS MIN VIH Input High Voltage All Logic Input Pins ● VIL Input Low Voltage All Logic Input Pins ● IC Input Current All Logic Input Pins ● Differential Driver Propagation Delay RL = 100Ω, CL = 100pF (Figures 2, 7) Differential Driver Propagation Delay with Single-Ended Load RL = 3k, CL = 100pF (Figures 3, 9) Single-Ended Driver Propagation Delay Differential Receiver Propagation Delay Single-Ended Receiver Propagation Delay TYP MAX UNITS Logic Inputs 2.0 V 0.8 V ±1.0 ±20 µA ● 40 120 ns ● 120 180 ns RL = 3k, CL = 100pF, (Figures 5, 10) (Note 5) ● 40 120 ns CL = 15pF (Figures 2, 11) ● 70 160 ns CL = 15pF (Figures 6, 12) (Note 5) ● 70 160 ns Inverting Receiver Propagation Delay in Keep-Alive Mode, SHDN = 0V, CPEN = VCC CL = 15pF (Figures 6, 12) (Note 5) ● 150 600 ns tSKEW Differential Driver Output to Output RL = 100Ω, CL = 100pF (Figures 2, 7) ● 10 50 ns tr, tf Differential Driver Rise/Fall Time RL = 100Ω, CL = 100pF (Figures 2, 7) ● 50 150 ns Differential Driver Rise/Fall Time with Single-Ended Load RL = 3k, CL = 100pF (Figures 3, 9) ● 50 150 ns Single-Ended Driver Rise/Fall Time RL = 3k, CL = 100pF (Figures 5, 10) (Note 5) ● 15 80 ns Differential Driver Output Active to Disable CL = 15pF (Figures 4, 8) ● 180 250 ns Any Receiver Output Active to Disable CL = 15pF (Figures 4, 13) ● 30 100 ns Differential Driver Enable to Output Active CL = 15pF (Figures 4, 8) ● 180 250 ns Any Receiver, Enable to Output Active CL = 15pF (Figures 4, 13) ● 30 100 Supply Rise Time from Shutdown or Receiver Keep-Alive C1 = C2 = 0.33µF, CVEE = 1µF ● 0.2 Switching Characteristics tPLH, tPHL tHDIS, tLDIS tENH, tENL VEER The ● denotes specifications which apply over the full operating temperature range. Note 1: Absolute maximum ratings are those values beyond which the life of a device may be impaired. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to ground unless otherwise specified. 4 Note 3: All typicals are given at VCC = 5V, TA = 25°C. Note 4: ILOAD is an external current being sunk into the VEE pin. Note 5: These specifications apply to the 24-pin SO Wide package only. ns ms LTC1323 U W TYPICAL PERFORMANCE CHARACTERISTICS Charge Pump Output Voltage vs Load Current –2.5 –3.0 –3.5 – 4.0 – 4.5 – 5.0 –5.5 – 6.0 5 5 4 4 3 2 1 0 –1 –2 –3 TA = 25°C VS = 5V –4 –5 0 5 10 20 15 LOAD CURRENT (mA) 25 50 100 200 300 500 1k 2k 3k LOAD RESISTANCE (Ω) 30 LTC1323 • TPC01 2.75 2.50 2.25 2.00 1.75 50 75 25 TEMPERATURE (˚C) 100 0 –1 –2 –3 –4 –5 50 100 200 300 500 1k 2k 3k LOAD RESISTANCE (Ω) 125 LTC1323 • TPC04 4.5 5k 10k LTC1323 • TPC03 Single-Ended Driver Swing vs Temperature 5 VS = 5V RL = 100Ω SINGLE-ENDED DRIVER OUTPUT (V) DIFFERENTIAL DRIVER OUTPUT (V) SUPPLY CURRENT (mA) 3.00 0 1 5k 10k 5.0 VS = 5V NO LOAD TA = 25°C VS = 5V 2 Differential Driver Swing vs Temperature 3.50 1.50 –50 –25 3 LTC1323 • TPC02 Supply Current vs Temperature 3.25 SINGLE-ENDED DRIVER OUTPUT (V) TA = 25°C VS = 5V RL(DIFF) = 100Ω RL(SE) = 3k TO GND VTXI = 5V DIFFERENTIAL DRIVER OUTPUT (V) CHARGE PUMP OUTPUT VOLTAGE (V) –2.0 Single-Ended Driver Swing vs Load Resistance Differential Driver Swing vs Load Resistance 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 LTC1323 • TPC05 4 3 VS = 5V RL = 3k TO GND 2 1 0 –1 –2 –3 –4 –5 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 LTC1323 • TPC06 5 LTC1323 U U U PI FU CTIO S LTC1323CS C1+ 1 LTC1323CSW 16 VCC C1+ 1 2 15 C2 + C1– TXD 3 14 C2 – TXDEN 4 13 VEE C1– SHDN 5 CHARGE PUMP DX RXEN 6 RXDO 7 GND 8 RX CHARGE PUMP 2 TXD 4 12 TXD 11 TXD + TXDEN 6 – SHDN 7 9 RXD+ RXEN 8 10 RXD C1+ 1 24 VCC 23 C2 + C1– 22 C2 – CPEN 3 – LTC1323CG 21 VEE DX 19 DX 28 VCC 2 27 C2 + CPEN 3 26 C2 – TXD 4 – TXI 5 TXD + TXDEN 6 20 TXD TXI 5 CHARGE PUMP 25 NC DX 24 NC 23 VEE DX 18 TXO SHDN 7 22 TXD – 17 RXI RXEN 8 21 TXD + RXO 9 20 TXO RX 16 RXI RXO 9 RX0 10 RX RXDO 11 15 RXD – RX0 10 14 RXD + RXDO 11 13 PGND NC 12 RX 18 RXI RX GND 12 19 RXI RX 17 RXD – 16 RXD + NC 13 RX GND 14 C1+ : C1 Positive Input. Connect a 0.33µF capacitor between C1+ and C1–. C1–: C1 Negative Input. Connect a 0.33µF capacitor between C1+ and C1–. CPEN: TTL Level Charge Pump Enable Input. With CPEN held low, the charge pump is enabled and the chip operates normally. When CPEN is pulled high, the charge pump is disabled as well as both drivers, the noninverting single-ended receiver, and the differential receiver. The inverting single-ended receiver (RXI) is kept alive to monitor the control line and ICC drops to 65µA. To turn off the receiver and drop ICC to 0.5µA, pull the SHDN pin high. TXD: Differential Driver Input (TTL compatible). TXI: Single-Ended Driver Input (TTL compatible). TXDEN: Differential Driver Output Enable (TTL compatible). A high level on this pin forces the differential driver into three-state; a low level enables the driver. This input does not affect the single-ended driver. SHDN: Shutdown Input (TTL compatible). When this pin is high, the chip is shut down. All driver and receiver outputs are three-state, the charge pump turns off, and the supply current drops to 0.5µA. A low level on this pin allows normal operation. 6 15 PGND RXEN: Receiver Enable (TTL compatible). A high level on this pin disables the receivers and three-states the logic outputs; a low level allows normal operation. RXO: Inverting Single-Ended Receiver Output. Remains active in the receiver keep-alive mode. RXO: Noninverting Single-Ended Receiver Output. RXDO: Differential Receiver Output. GND: Signal Ground. Connect to PGND with 24-pin package. PGND: Power ground is connected internally to the charge pump and differential driver. Connect to the GND pin. RXD+: Differential Receiver Noninverting Input. When this pin is ≥200mV above RXD–, RXDO will be high; when this pin is ≥ 200mV below RXD–, RXDO will be low. RXD–: Differential Receiver Inverting Input. RXI: Noninverting Receiver Input. This input controls the RXO output. RXI: Inverting Receiver Input. This input controls the RXO output. In receiver keep-alive mode (CPEN high, SHDN low), this receiver can be used to monitor a wake-up control signal. LTC1323 U U U PI FU CTIO S C2 –: C2 Negative Input. Connect a 0.33µF capacitor between C2+ and C2 –. TXO: Single-Ended Driver Output. TXD+: Differential Driver Noninverting Output. TXD–: Differential Driver Inverting Output. C2+: C2 Positive Input. Connect a 0.33µF capacitor between C2+ and C2–. VEE: Negative Supply Charge Pump Output. Requires a 1µF bypass capacitor to ground. If an external load is connected to the VEE pin, the bypass capacitor value should be increased to 4.7µF. VCC: Positive Supply Input. 4.5V ≤ VCC ≤ 5.5V. Requires a 1µF bypass capacitor to ground. TEST CIRCUITS TXD + R VOD TXI R CL RXD+ RL TXD – VOC CL RXD+ RXDO RXD – TXI TXD + RL TXD – 15pF RL CL CL TXD – LTC1323 • F03 LTC1323 • F01 LTC1323 • F02 Figure 1 Figure 2 Figure 3 VCC S1 TXI 500Ω TXO RXI RXO RXI RXO OUTPUT RL CL CL CL CL S2 LTC1323 • F04 LTC1323 • F05 Figure 4 LTC1323 • F06 Figure 5 Figure 6 U W SWITCHI G WAVEFOR S 3V 1.5V TXD f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V 0V tPLH tPHL VO 90% 50% 10% –VO VDIFF = V(TXD +) – V(TXD – ) 1/2 VO tr 90% 50% 10% tf TXD – VO TXD + tSKEW tSKEW LTC1323 • F07 Figure 7. Differential Driver 7 LTC1323 U W SWITCHI G WAVEFOR S 3V 1.5V TXDEN 0V f = 1MHz: tr ≤ 10ns: tf ≤ 10ns tZL tLZ 5V TXD+, TXD – 2.3V OUTPUT NORMALLY LOW VOL tZH OUTPUT NORMALLY HIGH VOH – TXD , TXD 1.5V 0.5V tHZ 0.5V + 2.3V 0V LTC1323 • F08 Figure 8. Differential Driver Enable and Disable 3V 1.5V TXD f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V 0V tPHL tPLH VOH TXD – 0V 0V VOL VOH TXD + VOL 90% 90% 0V 10% 0V 10% tr tf LTC1323 • F09 Figure 9. Differential Driver With Single-Ended Load 3V 1.5V TXI f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V 0V tPHL VOH TXO tPLH 90% 90% 0V 10% VOL 0V 10% tr LTC1323 • F10 tr Figure 10. Single-Ended Driver V OD2 + – 0V (RXD ) – (RXD ) f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 0V –VOD2 tPLH tPHL VOH RXDO VOL 1.5V 1.5V LTC1323 • F11 Figure 11. Differential Receiver 8 LTC1323 U W SWITCHI G WAVEFOR S VIH f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V RXI, RXI 1.5V VIL tPHL tPLH VOH 2.4V RXI 0.8V VOL VIH 1.5V RXI 1.5V V LTC1323 • F12 Figure 12. Single-Ended Receiver 3V 1.5V RXEN f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 0V tZL 1.5V tLZ 5V RXO, RXO, RXDO 2.3V OUTPUT NORMALLY LOW VOL tZH OUTPUT NORMALLY HIGH VOH 0.5V tHZ 0.5V 2.3V RXO, RXO, RXDO 0V LTC1323 • F13 Figure 13. Receiver Enable and Disable U U W U APPLICATIO S I FOR ATIO Functional Description The “serial port” on the back of an Apple-compatible computer or peripheral is a fairly versatile “multi-protocol” connector. It must be able to connect to a wide bandwidth LAN (an AppleTalk/LocalTalk network), which requires a high speed differential transceiver to meet the AppleTalk specification, and it must also be able to connect directly to a printer or modem through a short RS232 style link. The LTC1323 is designed to provide all the functions necessary to implement such a port on a single chip. Two versions of the LTC1323 are available: a 16-pin SO version which provides the minimum solution for interfacing to an AppleTalk network in a smaller package, and a larger 24-pin SO Wide version which additionally includes all the handshaking lines required to implement a complete AppleTalk/ modem/printer serial port. All LTC1323s run from a single 5V power supply while providing true single-ended compatibility, and include a 0.5µA low power shutdown mode to improve lifetime in battery-powered devices. The 24pin SO Wide version also includes a receiver keep-alive mode for monitoring external signals while drawing 65µA typically. The LTC1323 includes an RS422-compatible differential driver/receiver pair for data transmission, with the driver specified to drive 2V into the 100Ω primary of a typical LocalTalk interface transformer/RFI interference network. Either output of the differential RS422 driver can also act as an single-ended driver, allowing the LTC1323 to communicate over a standard serial connection. The 24-pin SO Wide LTC1323 also includes an extra single ended only driver and two extra RS232-compatible single-ended receivers for handshaking lines. All versions include an onboard charge pump to provide a regulated – 5V supply required for the single-ended drivers. The charge pump can also provide up to 10mA of external load current to power other circuitry. 9 LTC1323 U U W U APPLICATIO S I FOR ATIO Driving Differential AppleTalk or Single-Ended Loads Power Shutdown The differential driver is able to drive either an AppleTalk load or a single-ended load such as a printer or modem. With a differential AppleTalk load, TXD+ and TXD – will typically swing between 1.2V and 3.5V (Figure 14a). With a single-ended 3k load such as a printer, either TXD+ or TXD – will meet the single-ended voltage swing requirement of ±3.7V (Figure 14b). An automatic switching circuit prevents the differential driver from overloading the charge pump if the outputs are shorted to ground while driving single-ended signals. This allows the second single-ended driver to continue to operate normally when the first is shorted, and allows external circuitry attached to the charge pump output to continue to operate even if there are faults at the driver outputs. The power shutdown feature of the LTC1323 is designed for battery-powered systems. When SHDN is forced high the part enters shutdown mode. In shutdown the supply current typically drops from 2.4mA to 0.5µA , the charge pump turns off, and the driver and receiver outputs are three-stated. VCC = 5V + 24 1µF EXTERNAL CHIP GND VEE LTC1323 13 21 + C1 VCC 12 –5.5V ≤ VEE ≤ –4.5V IVEE ≤ 10mA LTC1323 • F15 Figure 14 Thermal Shutdown Protection The LTC1323 includes a thermal shutdown circuit which protects against prolonged shorts at the driver outputs. If a driver output is shorted to another output or to the power supply, the current will be initially limited to a maximum of 500mA. When the die temperature rises above 150°C, the thermal shutdown circuit disables the driver outputs. When the die cools to about 130°C, the outputs are reenabled. If the short still exists, the part will heat again and the cycle will repeat. This oscillation occurs at about 10Hz and prevents the part from being damaged by excessive power dissipation. When the short is removed, the part will return to normal operation. 10 The 24-pin SO Wide version of the LTC1323 also features a power saving receiver keep-alive mode. When CPEN is pulled high the charge pump is turned off and the outputs of both drivers, the noninverting single-ended receiver and the differential receiver are forced into three-state. The inverting single-ended receiver (RXI) is kept alive with ICC dropping to 65µA and the receiver delay time increasing to a maximum of 400ns. The receiver can then be used to monitor a wake-up control signal. Charge Pump Capacitors and Supply Bypassing IVEE 4.7µF Receiver Keep-Alive Mode (24-Pin SO Wide Only) The LTC1323 requires two external 0.33µF capacitors for the charge pump to operate: one from C1+ to C1– and one from C2 + to C2 –. These capacitors should be low ESR types and should be mounted as close as possible to the LTC1323. Monolithic ceramic capacitors work well in this application. Do not use capacitors greater than 2µF at the charge pump pins or internal peak currents can rise to destructive levels. The LTC1323 also requires that both VCC and VEE be well bypassed to ensure proper charge pump operation and prevent data errors. A 1µF capacitor from VCC to ground is adequate. A 1µF capacitor is required from VEE to ground and should be increased to 4.7µF if an external load is connected to the VEE pin. Ceramic or tantalum capacitors are adequate for power supply bypassing; aluminum electrolytic capacitors should only be used if their ESR is low enough for proper charge pump operation. Inadequate bypass or charge pump capacitors will cause the charge pump output to go out of regulation prematurely, degrading the output swing at the SINGLEENDED driver outputs. LTC1323 U U W U APPLICATIO S I FOR ATIO Driving an External Load from VEE the LTC1323 uses a single supply differential driver, the resistor values should be reduced to 5Ω to 10Ω to guarantee adequate voltage swing on the cable (Figure 16a). In most applications, removing the resistors completely does not cause an increase in EMI as long as a shielded connector and cable are used (Figure 16b). With the resistors removed the only DC load is the primary resistance of the LocalTalk transformer. This will increase the DC standby current when the driver outputs are active, but does not adversely affect the drivers because they can handle a direct indefinite short circuits without damage. Transformer primary resistance should be above 15Ω to keep the LTC1323 operating normally and prevent it from entering thermal shutdown. For maximum swing and EMI immunity, a ferrite bead and capacitor T network can be used (Figure 16c). An external load may be connected between ground and the VEE pin as shown in Figure 15. The LTC1323 VEE pin will sink up to a maximum of 10mA while maintaining the pin voltage between – 4.5V and – 5.5V. If an external load is connected, the VEE bypass capacitor should be increased to 4.7µF. Both LTC1323 and the external chip should have separate VCC bypass capacitors but can share the VEE capacitor. EMI Filter Most LocalTalk applications use an electromagnetic interference (EMI) filter consisting of a resistor-capacitor T network between each driver and receiver and the connector. Unfortunately, the resistors significantly attenuate the drivers output signals before they reach the cable. Because 5Ω TO 10Ω VCC = 5V FERRITE BEAD 5Ω TO 10Ω 100pF + 24 1µF 13 21 + (a) EXTERNAL CHIP GND VEE LTC1323 100pF 100pF C1 VCC 12 FERRITE BEAD (b) (c) LTC1323 • F16 Figure 16. EMI Filters IVEE 4.7µF –5.5V ≤ VEE ≤ –4.5V IVEE ≤ 10mA LTC1323 • F15 Figure 15 U TYPICAL APPLICATIONS N Typical LocalTalk Connection 5V + 1µF 16 1 0.33µF 2 15 CHARGE PUMP 14 13 0.33µF 1µF DATA IN TX ENABLE SHDN RX ENABLE DATA OUT 3 12 TX LocalTalk TRANSFORMER 11 4 5 6 7 100pF + LTC1323CS 120Ω 100pF 10 RX 8 100pF 9 LTC1323 • TA02 100pF Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 11 LTC1323 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 0.205 – 0.212** (5.20 – 5.38) 0.397 – 0.407* (10.07 – 10.33) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 0.068 – 0.078 (1.73 – 1.99) 0° – 8° 0.005 – 0.009 (0.13 – 0.22) 0.301 – 0.311 (7.65 – 7.90) 0.0256 (0.65) BSC 0.022 – 0.037 (0.55 – 0.95) 0.002 – 0.008 (0.05 – 0.21) 0.010 – 0.015 *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH (0.25 – 0.38) SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 G28 SSOP 0694 S Package 16-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.386 – 0.394* (9.804 – 10.008) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 16 0.004 – 0.010 (0.101 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 15 13 14 12 11 10 9 0° – 8° TYP 0.016 – 0.050 0.406 – 1.270 0.050 (1.270) TYP 0.014 – 0.019 (0.355 – 0.483) 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE S16 0695 3 2 1 5 4 7 6 8 SW Package 24-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.598 – 0.614* (15.190 – 15.600) 0.291 – 0.299** (7.391 – 7.595) 0.010 – 0.029 × 45° (0.254 – 0.737) 0.093 – 0.104 (2.362 – 2.642) 0.037 – 0.045 (0.940 – 1.143) 24 23 22 21 20 19 18 17 16 15 14 13 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) NOTE 1 0.050 (1.270) TYP 0.014 – 0.019 0.016 – 0.050 (0.356 – 0.482) (0.406 – 1.270) NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS. *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 12 Linear Technology Corporation 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0.004 – 0.012 (0.102 – 0.305) 1 2 3 4 5 6 7 8 9 10 11 12 S24 (WIDE) 0695 LT/GP 1194 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1994