lx1665 Microsemi Corporation, lx1665 Datasheet
lx1665
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lx1665 Summary of contents
Page 1
... Expensive Current Sense Resistors. Current-sensing mechanism can use PCB trace resistance or the parasitic resistance of the main inductor. The LX1664A and LX1665A have reduced current sense com- parator threshold for optimum perfor- mance using a sense resistor. For applica- tions requiring a high degree of accuracy, a conventional sense resistor can be used to sense current ...
Page 2
... Over-Voltage Protection and Power Good Flag. The OVP output in the LX1665 & LX1665A can be used to drive an SCR crowbar circuit to protect the load in the event of a short-circuit of the main MOSFET. The LX1665 & LX1665A also have a logic- level Power Good Flag to signal when the output voltage is out of specified limits ...
Page 3
... SS Sink Current Sat Voltage V OL Supply Current Section Dynamic Operating Current I CD Power Good / Over-Voltage Protection Section (LX1665 Only) Lower Threshold Hysteresis Power Good Voltage Low Over-Voltage Threshold OVP Sourcing Current Linear Regulator Section Output Voltage Setpoint Accuracy Output Temperature Drift ...
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... LX1664/64A, LX1665/65A D * Nominal = DAC setpoint voltage with no adaptive output voltage positioning. Note: Adaptive Transient Voltage Output In order to improve transient response a 40mV offset is built into the Current Sense comparator. At high currents, the peak output voltage will be lower than the nominal set point, as shown in Figure 1 ...
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... Non-Synchronous Operation FIGURE 4 — Efficiency Test Results: Synchronous Operation, V Note: Non-synchronous operation not recommended for 12V operation, due to power loss in Schottky diode. LX1664/1664A, LX1665/65A PWM C 5-B ONTROLLERS WITH 100 Output Set Point EFFICIENCY AT 3 ...
Page 6
... PWM Latch DOM R Q Break Before Make 0.7V SYNC EN Comp OV Comp UV Comp LX1665/1665A ONLY Linear Op Amp Note: Pin numbers are correct for LX1665/1665A, 18-pin package. * Not connected on LX1664/1664A. ** 60mV in LX1664A/1665A TDRV 17 GND 16 BDRV OV* 12 PWRGD* 10 ...
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... FET is replaced by a Schottky diode). Both power and signal ground of the device. Gate drive for top MOSFET. This pin is a separate power supply input for the top drive. Can be connected to a charge pump when only 12V is available. LX1664/1664A, LX1665/65A PWM C 5-B UTPUT ONTROLLERS WITH ...
Page 8
... The controller is inherently protected from an over-voltage condi- tion due to its constant OFF-time architecture. However, should a failure occur at the power switch, an over-voltage drive pin is provided (on the LX1665 only) which can drive an external SCR crowbar (Q removed and power recycled for the LX1665 to resume normal operation (See Figure 9) ...
Page 9
... VID0 VID0 BDRV 5 VID1 VID1 6 VID2 VID2 7 VID3 VID3 8 VID4 VID4 16-pin Narrow Body SOIC FIGURE 7 — LX1664 In A Non-Synchronous / Socket 7 Power Supply Application LX1664/1664A, LX1665/65A PWM C 5-B ONTROLLERS WITH 12V 5V 6.3V C 1500µ 1µ ...
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... LX1664/64A, LX1665/65A 0.1µ VID0 5 VID1 6 VID2 7 VID3 8 VID4 9 FIGURE 8 — VRM 8.2 (Pentium II / Deschutes) Reference Design With Loss-Less Current Sensing C 3 0.1µ VID0 5 VID1 6 VID2 7 VID3 ...
Page 11
... T S OUT Where I is fixed at 200µA and f is the switching frequency DIS S (recommended to be around 200kHz for optimal operation and component selection). LX1664/1664A, LX1665/65A PWM C 5-B UTPUT ONTROLLERS WITH ...
Page 12
... The LX166x family offers two different comparator thresholds. The LX1664 & 1665 have a threshold of 100mV, while the LX1664A and LX1665A have a threshold of 60mV. The 60mV threshold is better suited to higher current loads, such as a Pentium II or Deschutes processor. ...
Page 13
... Current R S2 Sense V CS Comparator FIGURE 11 — Current Sense Circuit LX1664/1664A, LX1665/65A PWM C 5-B UTPUT ONTROLLERS WITH CURRENT LIMIT The current flowing through the inductor is a triangle wave. If the sensor components are selected such that: ...
Page 14
... LX1664/64A, LX1665/65A D CURRENT LIMIT (continued) In cases where large that the trip point current would L be lower than the desired short-circuit current limit, a resistor (R can be put in parallel with shown in Figure 11. The selection ...
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... To avoid a load transient on the switching output affecting the linear regulator, follow these guidelines: 1) Separate 5V supply traces to switching & linear FETs as much as possible. 2) Place capacitor C as close to drain Typical transient response is shown in Figure 13. LX1664/1664A, LX1665/65A PWM C 5-B UTPUT ONTROLLERS WITH ...
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... LX1664/64A, LX1665/65A D LINEAR REGULATOR (continued) TABLE 6 - Resistors Settings for Linear Regulator Output Voltage Ω Ω Ω Ω Ω Capacitor Selection Referring to the Product Highlight schematic on the front page, the standard value to use as the linear regulator stage output capacitor is on the order of 330µ ...
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... PRODUCTION DATA - Information contained in this document is proprietary to LinFinity, and is current as of publication date. This document may not be modified in any way without the express written consent of LinFinity. Product processing does not necessarily include testing of all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time. LX1664/1664A, LX1665/65A PWM C 5-B ...