NCP3012 View Datasheet(PDF) - ON Semiconductor
Part Name
Description
Manufacturer
NCP3012 Datasheet PDF : 26 Pages
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NCP3012
Master/Slave Synchronization
The SYNC pin performs two functions. The first function
is to identify if the device is a master or a slave. The second
function is to either synchronize to an external clock
(Slave Mode) or provide an external clock that is shifted by
180° from the high side switch (Master Mode). The typical
application circuit for this is shown in Figure 20.
HSDR
MASTER
VIN
SYNC 1
VIN
SYNC 2
SLAVE
60kW
HSDR
Figure 20. Master Slave Typical Application
Upon initial power up, the device determines if it is a
Master or Slave by applying 1.25 V to the SYNC pin and
determining whether the current draw from the pin is greater
than the Master Threshold Current (ISYNCTRIP). If
ISYNCTRIP is exceeded then the device enters master mode.
If the current is less than ISYNCTRIP the device enters slave
mode. Once identified as a Master, the device switching
frequency is increased by 15%. See Equation 2.
RMaster
+
SYNCref
ISYNCTRIP
RMaster = Master Select Resistor (W)
SYNCref = Sync Reference Voltage (V)
ISYNCTRIP = Master Threshold Current (A)
(eq. 2)
Master
HSDRV
Slave
HSDRV
0−50%
Duty
Cycle
Vref = 1.25 V
Pulse
Detect
Master
Hold
Detection Result
SYNC1 Time > 40 ms
Voltage
Vref = 1.25 V
Time > 40 ms
0−50%
Duty
Cycle
SYNC 2
Voltage
ITRIP = 10 mA
SYNC 1
Current
Indication
of Master
SYNC 2
Current
Indication
of Slave
40 ms
Slave Pull
Down Turn on
0 mA
Input
Voltage
Figure 21. Master Slave Typical Waveforms
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