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ISL6566IRZ-T Datasheet(PDF) 11 Page - Intersil Corporation |
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ISL6566IRZ-T Datasheet(HTML) 11 Page - Intersil Corporation |
11 / 28 page 11 FN9178.3 July 25, 2005 The ISL6566 supports MOSFET rDS(ON) current sensing to sample each channel’s current for channel-current balance. The internal circuitry, shown in Figure 5 represents channel n of an N-channel converter. This circuitry is repeated for each channel in the converter, but may not be active depending on the status of the PVCC3 and PVCC2 pins, as described in the PWM Operation section. The ISL6566 senses the channel load current by sampling the voltage across the lower MOSFET rDS(ON), as shown in Figure 5. A ground-referenced operational amplifier, internal to the ISL6566, is connected to the PHASE node through a resistor, RISEN. The voltage across RISEN is equivalent to the voltage drop across the rDS(ON) of the lower MOSFET while it is conducting. The resulting current into the ISEN pin is proportional to the channel current, IL. The ISEN current is sampled and held as described in the Current Sampling section. From Figure 5, the following equation for In is derived where IL is the channel current. Output Voltage Setting The ISL6566 uses a digital to analog converter (DAC) to generate a reference voltage based on the logic signals at the VID pins. The DAC decodes the 5 or 6-bit logic signals into one of the discrete voltages shown in Tables 2, 3, and 4. Each VID pin is pulled up to an internal 1.2V voltage by a weak current source (40 µA current), which decreases to 0 as the voltage at the VID pin varies from 0 to the internal 1.2V pull-up voltage. External pull-up resistors or active-high output stages can augment the pull-up current sources, up to a voltage of 5V. .The ISL6566 accommodates three different DAC ranges: Intel VRM9.0, AMD Hammer, or Intel VRM10.0. The state of the VRM10 and VID12.5 pins decide which DAC version is active. Refer to Table 1 for a description of how to select the desired DAC version. FIGURE 4. SAMPLE AND HOLD TIMING TIME PWM IL ISEN SWITCHING PERIOD SAMPLING PERIOD OLD SAMPLE CURRENT NEW SAMPLE CURRENT FIGURE 5. ISL6566 INTERNAL AND EXTERNAL CURRENT- SENSING CIRCUITRY FOR CURRENT BALANCE In ISEN IL rDS ON () RISEN -------------------------- = - + ISEN(n) RISEN SAMPLE & HOLD ISL6565A INTERNAL CIRCUIT EXTERNAL CIRCUIT VIN CHANNEL N UPPER MOSFET CHANNEL N LOWER MOSFET - + IL rDS ON () IL In IL rDS ON () RISEN ---------------------- =(EQ. 3) TABLE 1. ISL6566 DAC SELECT TABLE DAC VERSION VRM10 PIN VID12.5 PIN VRM10.0 high - VRM9.0 low high AMD HAMMER low low TABLE 2. AMD HAMMER VOLTAGE IDENTIFICATION CODES VID4 VID3 VID2 VID1 VID0 VDAC 111 11 Off 111 10 0.800 111 01 0.825 111 00 0.850 110 11 0.875 110 10 0.900 110 01 0.925 110 00 0.950 101 11 0.975 101 10 1.000 101 01 1.025 101 00 1.050 100 11 1.075 100 10 1.100 100 01 1.125 100 00 1.150 011 11 1.175 011 10 1.200 011 01 1.225 011 00 1.250 010 11 1.275 010 10 1.300 ISL6566 ISL6566 |
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