Typical application circuits – Rainbow Electronics MAX5071 User Manual
Page 16
MAX5070/MAX5071
Advance Clock Output (ADV_CLK) (MAX5071C)
ADV_CLK is an advanced pulse output provided to
facilitate the easy implementation of secondary-side
synchronous rectification using the MAX5071C. The
ADV_CLK pulse width is 85ns (typically) with its rising
edge leading the rising edge of OUT by 110ns. Use
this leading pulse to turn off the secondary-side syn-
chronous-rectifier MOSFET (QS) before the voltage
appears on the secondary (see Figure 8). Turning off
the secondary-side synchronous MOSFET earlier
avoids the shorting of the secondary in the forward
converter. The ADV_CLK pulse can be propagated to
the secondary side using a pulse transformer or high-
speed optocoupler. The 85ns pulse, with 3V drive volt-
age (10mA source), significantly reduces the
volt-second requirement of the pulse transformer and
the advanced pulse alleviates the need for a high-
speed optocoupler.
Thermal Shutdown
When the MAX5070/MAX5071s’ die temperature goes
above +150°C, the thermal-shutdown circuitry will shut
down the 5V reference and pull OUT low.
High-Performance, Single-Ended, Current-Mode
PWM Controllers
16
______________________________________________________________________________________
t
ADV_CLK
= 110ns
t
PULSE
= 85ns
OUT
ADV_CLK
R
T
/C
T
Figure 4. ADV_CLK
Typical Application Circuits
R
T
R1
R2
1
2
4
3
VREF
V
CC
GND
OUT
COMP
FB
R
T
/C
T
CS
8
7
5
6
MAX5070A
MAX5070B
C
T
R
ST
V
IN
C
ST
V
OUT
N
R
CS
Figure 5. MAX5070A/MAX5070B Typical Application Circuit (Isolated Flyback with Primary-Side Regulation)