max5075aauat Maxim Integrated Products, Inc., max5075aauat Datasheet - Page 6

• Manufacturer Part Number: max5075aauat
• Description: Max5075 Push-pull Fet Driver With Integrated Oscillator And Clock Output
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5075 is a +4.5V to +15V push-pull, current-fed
topology driver subsystem with an integrated oscillator
for use in 48V module power supplies.
The MAX5075 features a programmable, accurate inte-
grated oscillator with a synchronizing clock output that
can be used to synchronize an external PWM stage. A
single external resistor programs the internal oscillator
frequency from 50kHz to 1.5MHz.
The MAX5075 incorporates a dual MOSFET driver with
±3A peak drive currents and a 50% duty cycle. The
MOSFET driver generates complementary signals to
drive external ground-referenced n-channel MOSFETs.
The MAX5075 is available with a clock output frequency
to MOSFET driver frequency ratios of 1x , 2x, and 4x.
An external resistor at RT programs the MAX5075
internal oscillator frequency from 50kHz to 1.5MHz. The
MAX5075A/B NDRV1 and NDRV2 switching frequen-
cies are one-half the programmed oscillator frequency
with a nominal 50% duty cycle. The MAX5075C NDRV1
and NDRV2 switching frequencies are one-fourth the
oscillator frequency.
Use the following formula to calculate the internal oscil-
lator frequency:
where f
resistor connected from RT to DGND in ohms.
Place a series combination of a 4.7kΩ resistor and a
1nF capacitor from RT to DGND for stability and to filter
out noise.
The MAX5075 provides a buffered clock output that can
be used to synchronize the oscillator input of a PWM con-
troller. CLK is powered from an internal 5V regulator and
sources/sinks up to 10mA. The MAX5075 has internal
CLK output frequency to NDRV1 and NDRV2 switching
frequency ratios set to 1x, 2x, or 4x (Table 1).
The MAX5075A has a CLK frequency to NDRV_ frequen-
cy ratio set to 1x. The MAX5075B has a CLK frequency to
NDRV_ frequency ratio set to 2x and the MAX5075C has
a CLK frequency to NDRV_ frequency ratio set to 4x.
There is a typical 30ns delay from CLK to NDRV_ output.
Push-Pull FET Driver with Integrated Oscillator
and Clock Output
6
_______________________________________________________________________________________
OSC
is the oscillator frequency and R
f
OSC
Detailed Description
=
Synchronizing Clock Output
32
10
xR
12
Internal Oscillator
RT
RT
is a
Pay careful attention to bypassing and grounding the
MAX5075. Peak supply and output currents may exceed
3A when driving large MOSFETs. Ground shifts due to
insufficient device grounding may also disturb other cir-
cuits sharing the same ground-return path. Any series
inductance in the V
paths can cause noise due to the very high di/dt when
switching the MAX5075 with any capacitive load. Place
one or more 0.1µF ceramic capacitors in parallel as close
to the device as possible to bypass V
ground plane to minimize ground-return resistance and
inductance. Place the external MOSFETs as close as
possible to the MAX5075 to further minimize board induc-
tance and AC path impedance.
Table 1. MAX5075 CLK Output Frequency
Figure 2. MAX5075 CLK Timing Diagrams
MAX5075A
MAX5075B
MAX5075C
NDRV2
NDRV1
NDRV2
NDRV1
NDRV2
NDRV1
PART
OSC
OSC
OSC
CLK
CLK
CLK
Applications Information
f
OSC
f
f
f
OSC
OSC
CLK
CC
/ 2
, NDRV1, NDRV2, and/or GND
MAX5075A
MAX5075B
MAX5075C
f
f
f
f
OSC
OSC
OSC
Supply Bypassing
NDRV1
CC
/ 2
/ 2
/ 4
to PGND. Use a
f
CLK
RATIO
to f
1
2
4
SW