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SP4446 Datasheet(PDF) 5 Page - Sipex Corporation |
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SP4446 Datasheet(HTML) 5 Page - Sipex Corporation |
5 / 10 page 5 Date: 1/2/06 SP4446 High Output Voltage Boost Regualtor, LCD Bias Regulator © Copyright 2006 Sipex Corporation APPLICATION INFORMATION: Continued The formula and table for the resistor selection are shown below: R1 = ( VOUT - 1 ) • R2 1.22 VOUT (V) R1 ( Ω)R2 (Ω) 12 1M 113K 15 1M 88.7K 18 1M 73.2K 20 1M 64.9K 30 1M 42.2K Table 3. Divider Resistor Selection Layout Considerations Both the input capacitor and the output capacitor should be placed as close as possible to the IC. This can reduce the copper trace resistance which di- rectly effects the input and output ripple. The feedback resistor network should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connectionforthefeedbackresistornetworkshould connect directly to the GND pin or to an analog ground plane that is tied directly to the GND pin. The inductor and the Schottky diode should be placed as close as possible to the switch pin to minimize the noise coupling to the other circuits, especially the feedback network. PIN Diode Driver The SP4446 can be used as PIN diode driver as shown in Figure. 2. Fig. 2. Pin Diode Driver 3.3V or 5V R1 1M C1 4.7uF 30V R2 42.2K U1 SP4446 1 2 3 4 5 SHDN Murata LQH32CN100K21 3 to 5 mA DS MBR0530 C2 47pF 1.22V L1 10uH 0.3A C3 2.2uF 3.3V or 5V R1 1M C1 4.7uF 30V R2 42.2K U1 SP4446 1 2 3 4 SW GND FB SHDN V IN Murata LQH32CN100K21 V IN 3 to 5 mA DS MBR0530 V OUT C2 47pF 1.22V L1 10uH 0.3A C3 2.2uF V IN DS C1 4.7uF Q1 MMBT2907A R1 1M R3 154K 20V 1.22V C2 47pF R2 64.9K U1 SP4446 1 2 3 4 5 SW GND FB SHDN V IN V OUT L1 10uH C3 2.2uF When the SP4446 is active, the voltage set at the emitter of the transistor exceeds the input volt- age, forcing the transistor into the saturation region. When the SP4446 is shut down, the input voltage exceeds the emitter voltage, thus the transistor becomes inactive and provides high- impedance isolation between the input and load. Efficiency will be slightly sacrificed because of the saturation voltage and base current of the PNP transistor. Fig. 3. Load Disconnect in Shutdown Two Resistors (R1=1MΩ, R2=42.2KΩ) are used to program the output voltage to be 30V. When input voltage is 3.3V or 5V, it can supply a maximum current of 3mA and 5mA to the load. Load Disconnect in Shutdown When SP4446 is shut down, the load is still connected to the input. In applications that re- quire output isolation during shutdown, an ex- ternalPNPtransistor(forexample MMBT2907A) can be added as shown in Figure 3. |
Similar Part No. - SP4446_06 |
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Similar Description - SP4446_06 |
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