LTC2846 Linear Technology, LTC2846 Datasheet
LTC2846
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LTC2846 Summary of contents
Page 1
... DTE or DCE interface port that supports the RS232, RS449, EIA530, EIA530-A, V.35, V.36 and X.21 protocols. All necessary cable termination is provided inside the LTC2846. The LTC2846 has a boost regulator that takes in a 3.3V input and switches at 1.2MHz, allowing the use of tiny, low cost capacitors and inductors 2mm or less in height. ...
Page 2
... SW Voltage ............................................... – 0.4V to 36V FB Voltage ............................................... – 0.3V to 2.5V Current into FB Pin .............................................. 1mA SHDN Voltage ........................................... – 0.3V to 10V Operating Temperature Range LTC2846C ............................................... LTC2846I ........................................... – Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL ...
Page 3
... OUT V and V 0.25V, Power Off No-Cable Mode or Driver Disabled (Figures 2, 13) (Figures 2, 13) (Figures 2, 13) – t (Figures 2, 13) PLH PHL (Figures 2, 13) LTC2846 = V , unless otherwise noted. (Notes 2, 3) SHDN IN MIN TYP MAX – 9.6 – 7.5 – 8.5 – 5.5 – 6.5 – 4.5 – 6.0 500 2 2 ...
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... LTC2846 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER V.11 Receiver V Input Threshold Voltage TH V Input Hysteresis TH R Input Impedance Rise or Fall Time Input to Output Rising PLH t Input to Output Falling PHL t Input to Output Difference, t V.35 Driver V Differential Output Voltage ...
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... 3.3 F and VEE unless otherwise IN V.28 Mode I vs Data Rate 1000 10000 10 20 DATA RATE (kBd) 2846 G05 LTC2846 MAX UNITS 0 0 300 ns 300 ns 3.6 V 1.280 V 360 0.05 %/V 1.6 MHz ...
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... LTC2846 TYPICAL PERFOR A CE CHARACTERISTICS V.11 Mode I vs Temperature CC 110 105 100 –40 – TEMPERATURE ( C) Boost Switching Regulator SHDN Pin Current vs Voltage SHDN PIN VOLTAGE ( DataSheet U .com ...
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... SW (Pin 36): Boost Switching Regulator Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. . See Table See Table 1. IN (Pin 31): Generated Negative Supply Voltage. Connect – (Pin 32): Capacitor C2 Negative Terminal. Connect a + – and (Pin 33): Capacitor C2 Positive Terminal. Connect a + – and C2 . LTC2846 sn2846 2846fs 7 ...
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... LTC2846 W BLOCK DIAGRA PGND SHDN DCE/DTE 8 4 DataSheet U .com BOOST SWITCHING REGULATOR GND SHDN GND 4 CHARGE PUMP – – – GND 125 50 50 ...
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... Figure 4. V.11, V.35 Receiver AC Test Circuit 50 125 125 Figure 7. V.35 Driver Common Mode Impedance Test Circuit + – CM Figure 10. Receiver Common Mode Impedance Test Circuit 2846 F12 Figure 12. V.28 Receiver Test Circuit LTC2846 + – CM 2846 F07 51.5 125 51.5 2846 F10 sn2846 2846fs 9 ...
Page 10
... IN 1.5V t PHL 90% 50% 10 SKEW INPUT 0V t PHL OUTPUT 1.65V (Note 4) (Note 5) 9.3V –6V 9.3V –6V 9.3V –6V 9.3V –6V 8V –6.5V 9.3V –6V 8.7V –8.5V Z 4.7V 0.3V 9.3V –6V 9.3V –6V 9.3V –6V 9.3V –6V 8V –6.5V 9.3V –6V 8.7V –8.5V Z 4.7V 0. with LTC2846 with LTC2846 A 2846 F13 2846 F14 sn2846 2846fs ...
Page 11
... Cable termination is provided on-chip, elimi- nating the need for discrete termination designs. A complete DCE-to-DTE interface operating in EIA530 mode is shown in Figure 17. The LTC2846 half of each port is used to generate and appropriately terminate the clock and data signals. The LTC2844 is used to generate the control signals along with LL (Local Loopback) ...
Page 12
... In this mode the LTC2846/LTC2844 supply current drops to less than 900 A and the LTC2846/LTC2844 driver out- puts are forced into a high impedance state. At the same time, the R2 and R3 receivers of the LTC2846 are differ- entially terminated with 103 and the other receivers DataSheet U ...
Page 13
... Alternatively, custom cables may contain termination in the cable head or route signals to various terminations on the board. The LTC2846/LTC2844 chip set solves the cable termina- tion switching problem by automatically providing the appropriate termination and switching on-chip for the V.10 (RS423), V.11 (RS422), V.28 (RS232) and V.35 electrical protocols ...
Page 14
... In V.11 mode, all switches are off except S1 of the LTC2846’s receivers which connects a 103 differential 1 Actually, there is no switch S1 in receivers R2 and R3. However, for simplicity, all termination networks on the LTC2846 can be treated identically assumed that an S1 switch exists and is always closed on the R2 and R3 receivers DataSheet U ...
Page 15
... DataSheet U .com W U 100 nals (A In V.35 mode, both switches S1 and S2 inside the LTC2846 are on, connecting a T network impedance as shown in Figure 27. The 30k input impedance of the receiver is placed in parallel with the T network termination, but does not affect the overall input impedance significantly. ...
Page 16
... APPLICATIO S I FOR ATIO Switching Regulator The circuit as shown in Figure 29 can provide up to 480mA drive the LTC2846’s transceiver as well as its companion chip in the DTE-DCE interface. In its shut down mode with the SHDN pin at 0V, the boost switching regulator draws less than 10 A. ...
Page 17
... The select bit M2 is floating, and IN therefore, internally pulled high. When the cable is pulled out, the interface will go into the no-cable mode. Power Dissipation Calculations The LTC2846 takes in a 3.3V supply and produces with an internal switcher at approximately 80% efficiency. V and V are in turn produced from V ...
Page 18
... 56% • (8V • 0.3mA) + 79% • (5.5V • 23mA) = 210mW • (4) So for an X.21 DCE port running at 10MBd, the LTC2846 EE dissipates approximately 918mW + 210mW = 1128mW while the LTC2845 dissipates 228mW. = – 5.5V: Compliance Testing 2.7mA 110mA The LTC2846/LTC2844 and LTC2846/LTC2845 chipsets 2mA have been tested by TUV Rheinland of North America Inc ...
Page 19
... 3.3V 12 C10 DCE/DTE LTC2846 13k 4.3k 2 TXD A (103) 14 TXD B 24 SCTE A (113) 11 SCTE B 15 TXC A (114) 12 TXC B 17 RXC A (115) 9 RXC B 3 RXD A (104) 16 RXD B ...
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... DataSheet U .com MBR0520 5 BOOST 4 35 SHDN SWITCHING REGULATOR CHARGE PUMP LTC2846 ...
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... GND LTC2844 DCE/DTE LTC2846 D1 MBR0520 13k 4. 3 DTE 2 29 TXD TXD SCTE SCTE ...
Page 22
... Figure 34. Controller-Selectable Multiprotocol DTE/DCE Port with RL, LL, TM and DB-25 Connector 22 4 DataSheet U .com BOOST 4 SHDN SWITCHING REGULATOR CHARGE PUMP LTC2846 DCE/DTE ...
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... CABLE WIRING FOR MODE SELECTION MODE PIN 18 PIN 21 V.35 PIN 7 PIN 7 RS449, V.36 NC PIN 7 RS232 PIN 7 NC CABLE WIRING FOR DTE/DCE SELECTION MODE PIN 25 DTE PIN 7 DCE NC LTC2846 DCE RXD A RXD B RXC A RXC B TXC A TXC B SCTE A SCTE B TXD A TXD B DB-25 CTS A CTS B DSR A DSR B DCD A DCD B DTR A DTR B ...
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... Companion to LTC1546 or LTC1543 for Control Signals Including LL 5-Driver/5-Receiver Companion to LTC1546 or LTC1543 for Control Signals Including LL, TM and RL 3-Driver/3-Receiver with Termination for Data and Clock Signals Companion to LTC2846 for Control Signals Including LL 5-Driver/5-Receiver Companion to LTC2846 for Control Signals Including LL, TM and RL www.linear.com 12.50 – ...