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STPD01 数据表(PDF) 22 Page - STMicroelectronics |
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STPD01 数据表(HTML) 22 Page - STMicroelectronics |
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22 / 43 page ![]() 7.11 Pulse skip At light loads, the device works in discontinuous conduction mode. Zero-cross comparator is implemented to detect when the coil current crosses the zero during TOFF (i.e. low-side MOSFET on). During the sleep periods of the DCM operations both power MOSFETs are off and the efficiency is improved according to that. Moreover, the sleep period is a function of the load. Since the device works at almost fixed frequency (only 500 kHz or 750 kHz are selectable by I2C) with fixed minimum Ton typically 100 ns and wide PVIN range, up to 26.4 V, pulse skipping operation occurs to guarantee the proper regulation to light load (or no load conditions). In addition, the pulse skip threshold (i.e. the voltage the device enters the pulse skip operation) can be properly selected to optimize the efficiency at light loads. 7.12 Bus timing As shown in the figure below, the data on the SDA line must be stable during the high semi-period of the clock. The high and low-state of the data line can only change when the clock signal on the SCL line is low. Figure 37. Data transfer validity SDA SCL Data line stable Data valid Data change allowed Each bus transaction begins with a “START” command which is defined as SDA transition from 1 to 0 with SCL high, and it is finished with a “STOP” command, which is defined as SDA transition from 0 to 1 with SCL high, as shown in Figure 38. START and STOP commands. Figure 38. START and STOP commands Stop Condition Start Condition SDA SCL The master generates the start command and transmits the 7-bit address and the read/write bit on SDA line. All slave devices compare the address sent by the master to their internal fixed addresses. Only the slave device, with a matching address, generates an ACK by pulling the SDA line low during the entire high period of the ninth SCL clock. The acknowledge bit is used to indicate a successful byte transfer. STPD01 Pulse skip DS13473 - Rev 1 page 22/43 |
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