l6730cqtr STMicroelectronics, l6730cqtr Datasheet - Page 26

• Manufacturer Part Number: l6730cqtr
• Description: Adjustable Step-down Controller With Synchronous Rectification
• Manufacturer: STMicroelectronics

Device description
Table 6.
5.11
Figure 21. Synchronization.
26/50
6.2K
4.3K
2.7K
1.8K
1.2K
11K
N.C
R1
0
Synchronization
The presence of many converters on the same board can generate beating frequency noise. To
avoid this it is important to make them operate at the same switching frequency. Moreover, a
phase shift between different modules helps to minimize the RMS current on the common input
capacitors.
devices can be synchronized simply connecting together the SYNCH pins. The device with the
higher switching frequency will be the Master while the other one will be the Slave. The Slave
controller will increase its switching frequency reducing the ramp amplitude proportionally and
then the modulator gain will be increased.
To avoid a huge variation of the modulator gain, the best way to synchronize two or more
devices is to make them work at the same switching frequency and, in any case, the switching
frequencies can differ for a maximum of 50% of the lowest one. If, during synchronization
between two (or more) L6730, it’s important to know in advance which the master is, it’s timely
to set its switching frequency at least 15% higher than the slave. Using an external clock signal
(f
(f
The phase shift between master and slaves is approximately done 180°.
EXT
SW
S/O/U pin; CC/O/U pin
) it is recommended to follow the below formula:
) to synchronize one or more devices that are working at a different switching frequency
Figure 21.
PWM SIGNALS
2.7K
2.7K
2.7K
2.7K
2.7K
2.7K
N.C
R2
0
shows the results of two modules in synchronization. Two or more
V
SOU
f
0.2
0.3
0.4
0.5
0.6
0.7
SW
/V
0
1
CCDR
f
EXT
1
3 ,
12V BUS
12V BUS
12V BUS
12V BUS
5V BUS
5V BUS
5V BUS
5V BUS
UVLO
f
SW
INDUCTOR CURRENTS
Not Latched
Not Latched
Not Latched
Not Latched
Latched
Latched
Latched
Latched
OVP
L6730C - L6730D
SINK CC
Not
Yes
Not
Yes
Not
Yes
Not
Yes