MAX17595EVKIT# Maxim Integrated, MAX17595EVKIT# Datasheet - Page 17

• Manufacturer Part Number: MAX17595EVKIT#
• Description: Power Management IC Development Tools MAX17595 Eval Kit
• Manufacturer: Maxim Integrated

Specifications of MAX17595EVKIT#

• Rohs: yes

typically, f
R
mines the amount of dither as follows:
where %DITHER is the amount of dither expressed as a
percentage of the switching frequency. Setting R
to 10 x R
The internal oscillator can be synchronized to an exter-
nal clock by applying the clock to the DITHER/SYNC pin
directly. The external clock frequency can be set any-
where between 1.1x and 1.8x times the programmable
switching frequency for the MAX17595/MAX17596. The
synchronization feature is not available in the MAX17597.
An external clock increases the maximum duty cycle by
a factor of (f
The MAX17595/MAX17596/MAX17597 include an inter-
nal transconductance error amplifier. The noninverting
input of the error amplifier is internally connected to the
internal reference and the inverting input is brought out
at the FB pin to apply the feedback signal. The internal
reference is linearly ramped up from 0V to 1.21V (typ)
when the device is enabled at turn-on. After soft-start, the
internal reference is connected to the bandgap.
In isolated applications, where an optocoupler is used to
transmit the control signal from the secondary side, the
emitter current of the optocoupler flows through a resis-
tor to ground to set up the feedback voltage. A shunt
regulator is usually employed as a secondary-side error
amplifier to drive the optocoupler photodiode to couple
the control signal to the primary. The loop compensation
is applied in the secondary side as an R-C network on the
shunt regulator. The MAX17595/MAX17596/MAX17597
error amp can be set up as a proportional gain ampli-
fier, or used to implement additional poles or zeros.
The Typical Application Circuits for the MAX17595/
MAX17596 use the internal error amplifier as a propor-
tional gain amplifier.
In nonisolated applications, the output voltage is divided
down with a voltage-divider to ground and is applied to
the FB pin. Loop compensation is applied at the COMP
pin as an R-C network from COMP to GND that imple-
ments the required poles and zeros, as shown in Figure
Maxim Integrated
DITHER
Error Amplifier and Loop Compensation
RT
connected from DITHER/SYNC to RT deter-
TRI
generates Q10% dither.
SYNC
should be set close to 1kHz. Resistor
%DITHER
/ f
SW
).
Synchronization (SYNC)
=
R
DITHER
R
RT
Peak-Current-Mode Controllers for
MAX17595/MAX17596/MAX17597
Flyback and Boost Regulators
DITHER
8. The boost converter application circuit of Figure 11 for
the MAX17597 uses this approach.
All connections carrying pulsed currents must be very
short and as wide as possible. The inductance of these
connections must be kept to an absolute minimum due to
the high di/dt of the currents in high-frequency-switching
power converters. This implies that the loop areas for
forward and return pulsed currents in various parts of the
circuit should be minimized. Additionally, small current
loop areas reduce radiated EMI. Similarly, the heatsink
of the MOSFET presents a dV/dt source; therefore,
the surface area of the MOSFET heatsink should be
minimized as much as possible.
Ground planes must be kept as intact as possible. The
ground plane for the power section of the converter
should be kept separate from the analog ground plane,
except for a connection at the least noisy section of the
power ground plane, typically the return of the input filter
capacitor. The negative terminal of the filter capacitor, the
ground return of the power switch and current-sensing
resistor, must be close together. PCB layout also affects
the thermal performance of the design. A number of
thermal vias that connect to a large ground plane should
be provided under the exposed pad of the part for
efficient heat dissipation. For a sample layout that
ensures first-pass success, refer to the MAX17595 evalu-
ation kit layout available at www.maximintegrated.com.
For universal AC input designs, follow all applicable
safety regulations. Offline power supplies can require UL,
VDE, and other similar agency approvals.
Figure 8. Error-Amplifier Compensation Network
C
R
Z
Z
Layout, Grounding and Bypassing
C
P
COMP
MAX17595
MAX17596
MAX17597
17