Datenblatt-Suchmaschine für elektronische Bauteile |
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CS5106LSWR24 Datenblatt(PDF) 10 Page - Cherry Semiconductor Corporation |
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CS5106LSWR24 Datenblatt(HTML) 10 Page - Cherry Semiconductor Corporation |
10 / 12 page FADJ and DLYSET Leads Amplifier A2 and transistor N3 create a current source fol- lower whose output is FADJ. An external resistor from FADJ to ground completes the loop. The voltage across the resistor is set by a buffered, trimmed, precision reference. In this fashion, an accurate current is created which is used to charge and discharge an internal capacitor thereby creat- ing an oscillator with a tight frequency tolerance. For FADJ resistor value selection, see Figure 3. Transistor N2 is in parallel with N3 and is used to created an independent cur- rent across the resistor from DLYSET to ground. This cur- rent is used to program the GATE non-overlap delay blocks in the main PWM drivers. For DLYSET resistor value selection, see Figure 4. Figure 3: SYNCOUT Frequency vs. FADJ Resistors Figure 4: GATE Non-Overlap Time vs. DLYSET Resistance Oscillator The oscillator generates two clock signals which are 180 degrees out of phase with respect to time. One clock signal feeds the main driver and the other feeds the auxiliary driver. Because the drivers are never turned on at the same time, ground noise and supply noise is minimized. The clock signals are actually 100ns pulse spikes. These spikes create a narrow driver turn-on window. This narrow win- dow prevents the driver from spurious turn on in the mid- dle of a clock cycle. The oscillator can be synchronized by an external clock (slave) or drive the clocks of other con- trollers (master). See Figure 5 for the relationship between SYNC, CLK, and GATE waveforms. Figure 5: SYNC, GATE and CLOCK waveforms . SYNCIN and SYNCOUT Leads Multiple supplies can be synchronized to one supply by using the SYNC leads. The SYNCIN and SYNCOUT pulses are always 180 degrees out of phase. The SYNCIN input is always in phase with the clock signal for the main driver and the SYNCOUT output is always in phase with the clock signal for the auxiliary driver. If the IC is being used as a slave, the incoming frequency must be within +10%, -20% of the programmed frequency set by its own FADJ resistor. If the frequency on the SYNCIN lead is outside the internal frequency by +25%, -35%, the SYNCIN input will be ignored. If the SYNC signal stops while the power supplies are in synchronized operation, the synchronized supplies will stop and restart free running. If the SYNCIN signal drifts out of frequency specification while the power sup- plies are in synchronized operation, the synchronized sup- plies will begin to free run without restarting. Slope Compensation DC-DC converters with current mode control require slope compensation to avoid instability at duty cycles greater than 50%. A slope is added to the current sense waveform (or subtracted from the voltage waveform) that is equal to a percentage (75% typical) of the down slope of the induc- tor current. In the application diagram shown, the boot- strap (flyback) transformer inductance can be chosen so that the duty cycle never exceeds 50% and therefore does not require slope compensation. The buck indicator in the forward converter would typically be chosen to work in continuous conduction mode with a maximum duty cycle of 50-60% and would require slope compensation. Slope compensation is accomplished as follows: R9 and C9 form a ramp waveform rising each time GATE 2 turns on. C9 is discharged through D3 to the same level each cycle regard- less of duty cycle. R10 and R11 are chosen to control the amount of slope compensation. C10 provides filtering for noise and turn-on spikes. To calculate the required slope compensation, calculate the buck indicator down current and the corresponding voltage slope at the current sense resistor - R12. The buck inductor down slope is: Inductor_Slope = )A µs ( VOUT + VQ5 L1(µH) SYNCOUT CLK1 GATE1 CLK2 GATE2 GATE2B SYNCIN Resistance (k W) 80 70 60 50 40 30 20 10 0 010 515 20 25 30 35 40 45 50 1100 900 800 600 500 400 300 200 100 0 010 20 30 40 50 80 70 700 1000 Resistance k W 60 Theory of Application: continued 10 |
Ähnliche Teilenummer - CS5106LSWR24 |
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Ähnliche Beschreibung - CS5106LSWR24 |
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