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SP505ACF Datasheet(PDF) 18 Page - Sipex Corporation |
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SP505ACF Datasheet(HTML) 18 Page - Sipex Corporation |
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18 / 35 page  18 Rev: A Date: 1/27/04 SP505 Multi–Mode Serial Transceiver © Copyright 2004 Sipex Corporation A typical +10V charge pump would require external clamping such as 5V zener diodes on V DD and VSS to ground. The +5V output has symmetrical levels as in the +10V output. The +5V is used in the following modes where RS- 423 (V.10) are used: RS-449, EIA-530, EIA- 530A and V.36. Phase 1 (±10V) — V SS charge storage — During this phase of the clock cycle, the positive side of capacitors C 1 and C2 are initially charged to +5V. Cl + is then switched to ground and the charge on C 1 – is transferred to C 2 –. Since C 2 + is connected to +5V, the voltage potential across capacitor C 2 is now 10V. Phase 1 (±5V) — V SS & VDD charge storage and transfer — With the C 1 and C2 capacitors initially charged to +5V, C l + is then switched to ground and the charge on C 1 – is transferred to the V SS storage capacitor. Simultaneously the C 2 – is switched to ground and 5V charge on C 2 + is transferred to the V DD storage capacitor. FEATURES… The SP505 is a highly integrated serial trans- ceiver that allows software control of its inter- face modes. Similar to the SP504, the SP505 offers the same hardware interface modes for RS-232 (V.28), RS-422A (V.11), RS-449, RS- 485, V.35, EIA-530 and includes V.36 and EIA- 530A. The interface mode selection is done via a 4–bit switch for the drivers and receivers. The SP505 is fabricated using low–power BiCMOS process technology, and incorporates a Sipex– patented (5,306,954) charge pump allowing +5V only operation. Each device is packaged in an 80–pin JEDEC Quad FlatPack package. The SP505 is ideally suited for wide area net- work connectivity based on the interface modes offered and the driver and receiver configura- tions. The SP505 has seven (7) independent drivers and seven (7) independent receivers. In V.35 mode, the SP505 includes the necessary components and termination resistors internal within the device for compliant V.35 operation. THEORY OF OPERATION The SP505 is made up of five separate circuit blocks — the charge pump, drivers, receivers, decoder and switching array. Each of these circuit blocks is described in more detail below. Charge–Pump The SP505 charge pump is based on the SP504 design where Sipex's patented charge pump design (5,306,954) uses a four–phase voltage shifting technique to attain symmetrical 10V power supplies. The charge pump still requires external capacitors to store the charge. In addi- tion the SP504 charge pump supplies +10V or +5V on V SS and VDD depending on the mode of operation. There is a free–running oscillator that controls the four phases of the voltage shifting. A description of each phase follows. The SP505 charge pump is used for RS-232 where the output voltage swing is typically +10V and also used for RS-423. However, RS- 423 requires the voltage swing on the driver output be between +4V to +6V during an open- circuit (no load). The charge pump would need to be regulated down from +10V to +5V. VCC = +5V –5V –5V +5V VDD Storage Capacitor C1 C2 C4 + ++ – – – VSS Storage Capacitor C3 + – Figure 46. Charge Pump Phase 1 for +5V. VCC = +5V +5V VDD Storage Capacitor C1 C2 C4 + ++ – – – VSS Storage Capacitor C3 + – –5V Figure 45. Charge Pump Phase 1 for +10V. |
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