max5059auit Maxim Integrated Products, Inc., max5059auit Datasheet - Page 13

• Manufacturer Part Number: max5059auit
• Description: Parallelable, Secondary-side Synchronous Rectifier Driver And Feedback-generator Controller Ics
• Manufacturer: Maxim Integrated Products, Inc.

The MOSFET drivers are synchronized to the primary-
side switching by using the BUFIN input. BUFIN
accepts the PWM information from the primary through
a high-speed optocoupler or through a small isolation
pulse transformer. Figures 2 through 6 show the inter-
face details using an optocoupler or a pulse trans-
former with two different kinds of primary-side PWM
controllers.
For proper operation, the MAX5051, MAX5042, and
MAX5043 devices generate a look-ahead signal that
precedes the actual switching of the primary MOSFETs
by a small amount of time, typically less than 100ns.
Additional circuitry may be required when the
MAX5058/MAX5059 are used with other primary-side
controllers not capable of providing a look-ahead signal.
Figure 2. Interface of MAX5058 to MAX5042/MAX5043 Using a High-Speed Optocoupler
Figure 3. Interface of MAX5059 to MAX5042/MAX5043 Using a High-Speed Optocoupler
Parallelable Secondary-Side Synchronous Rectifier
Driver and Feedback-Generator Controller ICs
______________________________________________________________________________________
MAX5042
MAX5043
MAX5042
MAX5043
PWMNEG
PPWM
REG5
PWMNEG
PPWM
REG5
BSS84
2kΩ
560Ω
BSS84
2kΩ
560Ω
OR EQUIVALENT
OPTOCOUPLER
HIGH-SPEED
PS9715
OR EQUIVALENT
OPTOCOUPLER
HIGH-SPEED
PS9715
MMBT3904
When BUFIN goes high, QREC goes high and QSYNC
goes low. When BUFIN goes low, QREC goes low and
QSYNC goes high.
The MAX5058/MAX5059 provide improved efficiency at
light loads by allowing discontinuous conduction oper-
ation. A zero-crossing comparator with inputs ZCP and
ZCN monitors the current through the freewheeling
MOSFET using a sense resistor at its source. The free-
wheeling MOSFET is turned off when the inductor cur-
rent is near zero. The actual threshold can be externally
adjusted. The Typical Application Circuit shows one
method for trip-point adjustment using components
R31 and R34.
BUFIN is internally clamped to 4V. Use a voltage-divider,
if necessary, to reduce any external voltage applied to
this pin to less than 4V.
1μF
330Ω
4.42kΩ
3.10kΩ
330Ω
V
BUFIN
GND
REG
(5V)
V
BUFIN
GND
MAX5058
REG
(10V)
MAX5059
13