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NQ20W20ETC20NRS-G Datasheet(PDF) 8 Page - SynQor Worldwide Headquarters |
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NQ20W20ETC20NRS-G Datasheet(HTML) 8 Page - SynQor Worldwide Headquarters |
8 / 9 page Product # NQ20x20ETC20 Phone 1-888-567-9596 www.synqor.com Doc.# 005-NS2020W Rev. C 03/06/09 Page 8 Input: Outputs: Current: Package: 9 - 20 V 0 - 20 V 20 A Eighth-brick Technical Specification APPLICATION CONSIDERATIONS Limited output voltage resolution: The internal voltage control feedback loop has limited resolution. Therefore, the output voltage will exhibit discrete steps as the loop responds to changes in line, load, trim, or remote sense. For instance, on close examination, the startup ramp has a “stair-step” shape. Likewise, a load transient response will be composed of multiple discrete steps. Input filtering: These modules should be connected to a low-impedance source. A highly inductive source can affect the stability of the module. An input capacitance must be placed directly adjacent to the input pin of the module, to minimize input ripple voltage and ensure module stability. Output capacitance: For stable operation of the module, there is no extra external capacitor required. To reduce the output ripple and improve dynamic response to a step load change, additional capacitance at the output can be used. Low ESR polymer and ceramic capacitors are recommended to improve the dynamic response of the module. In many applications, however, additional external output capacitance is a requirement which will cause the startup time to change. Remote sense (S option): Vout remote sensing is provided to achieve proper regulation at the load points and reduce effects of distribution losses on output line. In the event of an open remote sense line, the module shall maintain local sense regulation through an internal resistor. The module shall correct for a total of 10% Vout. Current limit: Available power is limited by output current in buck mode (Vin>Vout), but by input current in boost mode (Vin<Vout). for Vin >Vout, Ilimit = 1.2 x Imax for Vin < Vout, Ilimit = 1.2 x Imax ( Vin ) Vout where Imax = Maximum rated output current Negative output: This series of converters can be set to negative output (see Figure B). Vin+ Vin+ ENABLE Vin- Vin-/ Vout+ Vout+ SENSE+ SENSE- TRIM Vout- Vout- 4 5 6 7 8 1 2 3 Cout1 Rtrim-up Cin1 Cin2 Dc/dc converter Figure B: Negative output setup Using this negative output setup impacts the available output voltage range and current limit. The output voltage range becomes 0 to Vmax - Vin, and the cur- rent limit is scaled by: Vin (Vin + Vout) Current monitor/trimmable current limit (C option): In addition to voltage trim, the C option offers an adjustable current limit input and a current monitor output. The C option also includes an ideal diode circuit in series with the Vout+ pin that prevents reverse current flow. This enables applications such as battery charging, current sharing, and current read back. Vin+ Vin- Vin+ ENABLE Vin- Vout+ Vout+ IMON IMON ITRIM VTRIM Vout- Vout- 4 5 6 7 8 1 2 3 Cout Rtrim-up RadjIlim Cin Dc/dc converter Figure C: Current monitor/trimmable current limit setup The Rtrim-up resistor increases the output voltage, identical in function to the S option. The RadjItrim resistor reduces the output current limit, according to the following equation: RadjItrim = [(0.0469Imax+Itrim)10200-10](Ω) 1.153 Imax + Itrim Alternatively, the Itrim pin can be driven from an external voltage source: V(pin5) = 2.085(Itrim/Imax) + 0.0953 where Itrim is the desired current limit setpoint If Ilimit is less than Itrim, then Ilimit takes precedence. The Imon pin voltage tracks the output current, as shown in figure 10. This pin has a 10kOhm output impedance. BASIC OPERATION AND FEATURES These converters use a digital controller for the buck stage and boost stage (see Figure A). It automatically changes operating mode (buck mode or boost) when the line voltage or output set point changes. Both stages are accomplished with synchronous rectifiers. Very high efficiency is maintained over wide input and output ranges by shifting operational modes and use of synchronous rectifiers. Vin+ Vin- Linput Cin1 Cin2 GATE_Q1 GATE_Q3 GATE_Q4 GATE_Q2 Q1 Q3 Q4 Q2 L Loutput JUMPER Cout1 Cout2 Vout+ Vout- Figure A: Topology W mode: Q3, Q4 are populated, Jumper is open. T mode: Q3, Q4 are open, Jumper is populated. The converter runs at a fixed frequency with a predictable EMI performance. This series of quarter-brick and eighth-brick converters use the industry standard footprint and pin-out configuration. CONTROL FEATURES REMOTE ON/OFF: The ON/OFF input permits the user to con- trol when the converter is on or off. Only Negative ON/OFF logic is available in this power module series. Negative logic ON/OFF signal turns the module OFF during logic high (leave the pin floating or set voltage between 1.8~3.3 V) and turns the module ON during logic low [tie to Vin(-)]. OUTPUT VOLTAGE TRIM: The output voltage can be programmed to any voltage between 0 V dc and Vmax by connecting one resistor between the Pin 6 (TRIM) pin and Pin 5 [Sense(-)]. For a desired output voltage, the value of the resistor should be: Rtrim-up(Vout) = [( 11830xVmax )_10912](Ω) Vout + 0.058 x Vmax Alternatively, the TRIM pin can be driven from an external voltage source: V(pin6) = 2.366 – 2.314 (Vout) Vmax where: Vout = desired output voltage V max = maximum rated output voltage To maintain the accuracy of the output voltage over load current, it is vital that any trim-up resistor be terminated directly to the converter’s Sense(-) pin (S option) or Vout(-) pin (C option), not at the connection to the load. A separate Kelvin connection to the PCB pad for the Vout(-) is optimal. PROTECTION FEATURES Input Under-Voltage Lockout: The converter is designed to turn off when the input voltage is too low, helping avoid an input system instability problem, described in more detail in the application note titled “Input System Instability”. The lockout circuitry is a comparator with DC hysteresis. When the input voltage is rising, it must exceed the typical Turn-On Voltage Threshold value (listed on the specification page) before the converter will turn on. Once the converter is on, the input voltage must fall below the typical Turn-Off Voltage Threshold value before the converter will turn off. Output Current Shutdown: To provide protection in an output short condition, the unit is equipped with internal short circuit protection. When the short protection is triggered, the unit shutdowns first. After approximately 16 ms inhibit time, the units turn on again. If the short condition remains, the current limit circuit will limit the output current. The units operate normally once the fault condition is removed. Internal Over-Voltage Protection: To fully protect from excessive output voltage, the output over-voltage shutdown circuitry is contained. This OVP is independent of the trimmed set point. The shutdown point is fixed on the standard option. Over-Temperature Shutdown: A temperature sensor on the converter senses the average temperature of the module. The thermal shutdown circuit is designed to turn the converter off when the temperature at the sensed location reaches the Over-Temperature Shutdown value. It will allow the converter to turn on again when the temperature of the sensed location falls by the amount of the Over-Temperature Shutdown Restart Hysteresis value. |
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