MAX5974AETE+ Maxim Integrated Products, MAX5974AETE+ Datasheet - Page 17

• Manufacturer Part Number: MAX5974AETE+
• Description: Current Mode PWM Controllers ACTIVE-CLAMPED CUR MODE PWM CONTLR
• Manufacturer: Maxim Integrated Products

Specifications of MAX5974AETE+

• Duty Cycle (max): 82 %
• Mounting Style: SMD/SMT
• Switching Frequency: 600 KHz
• Operating Supply Voltage: 12 V to 21 V
• Supply Current: 1.8 mA
• Maximum Operating Temperature: + 85 C
• Fall Time: 14 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 27 ns
• Package / Case: TQFN-16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

startup to provide a slow and smooth increase of the
duty cycle to its steady-state value. Calculate the value
of C
where I
ing soft-start and t
A resistor can also be added from the SS pin to GND to
clamp V
cycle to be less than 80% (see the Duty-Cycle Clamping
section).
The NDRV output drives an external n-channel MOSFET.
NDRV can source/sink in excess of 650mA/1000mA
peak current; therefore, select a MOSFET that yields
acceptable conduction and switching losses. The exter-
nal MOSFET used must be able to withstand the maxi-
mum clamp voltage.
Figure 3. Dead Time Between AUXDRV and NDRV
SS
SS-CH
as follows:
SS
< 2V and, hence, program the maximum duty
(10FA typ) is the current charging C
n-Channel MOSFET Gate Driver
BLANKING, t
SS
DEAD TIME, t
C
SS
is the programmed soft-start time.
AUXDRV
=
NDRV
I
BLK
SS-CH
DT
2V
Active-Clamped, Spread-Spectrum,
×
t
SS
Current-Mode PWM Controllers
SS
dur-
The AUXDRV output drives an external p-channel
MOSFET with the aid of a level shifter. The level shifter
consists of C
Application Circuits. When AUXDRV is high, C
recharged through D5. When AUXDRV is low, the gate
of the p-channel MOSFET is pulled below the source by
the voltage stored on C
Add a zener diode between gate to source of the exter-
nal n-channel and p-channel MOSFETs after the gate
resistors to protect V
maximum rating during transient condition (see the
Typical Application Circuits).
Dead time between the main and AUX output edges
allow ZVS to occur, minimizing conduction losses and
improving efficiency. The dead time (t
both leading and trailing edges of the main and AUX out-
puts as shown in Figure 3. Connect a resistor between
DT and GND to set t
400ns:
AUX
p-Channel MOSFET Gate Driver
, R
R
AUX
DT
DT
GS
, and D5 as shown in the Typical
AUX
=
to any value between 40ns and
from rising above its absolute
10k
40ns
, turning on the pFET.
Ω
×
t
DT
DT
) is applied to
Dead Time
AUX
17
is