MAX5080EVKIT Maxim Integrated Products, MAX5080EVKIT Datasheet - Page 11

• Manufacturer Part Number: MAX5080EVKIT
• Description: EVAL KIT FOR MAX5080
• Manufacturer: Maxim Integrated Products

Specifications of MAX5080EVKIT

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.3V
• Current - Output: 1A
• Voltage - Input: 4.5 ~ 40V
• Regulator Topology: Buck
• Frequency - Switching: 250kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MAX5080
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

For applications that do not require a 4.5V minimum
input, use the MAX5081. In this device the charge
pump is omitted and the input voltage range is from
7.5V to 40V. In this situation the boost diode and the
boost capacitor are still required (see the MAX5081
Typical Operating Circuit).
DVREG is the supply input for the internal high-side
MOSFET driver. The power for DVREG is derived from
the output of the internal regulator (REG). Connect
DVREG to REG externally. We recommend the use of
an RC filter (1Ω and 0.47µF) from REG to DVREG to fil-
ter the noise generated by the switching of the charge
pump. In the MAX5080, the high-side drive supply is
generated using the internal charge pump along with
the bootstrap diode and capacitor. In the MAX5081, the
high-side MOSFET driver supply is generated using
only the bootstrap diode and capacitor.
The output of the internal error amplifier (COMP) is avail-
able for frequency compensation (see the Compensation
Design section). The inverting input is FB, the noninvert-
ing input SS, and the output COMP. The error amplifier
has an 80dB open-loop gain and a 1.8MHz GBW prod-
uct. See the Typical Operating Character-istics for the
Gain and Phase vs. Frequency graph.
With SYNC tied to SGND, the MAX5080/MAX5081 use
their internal oscillator and switch at a fixed frequency
of 250kHz. For external synchronization, drive SYNC
with an external clock from 150kHz to 350kHz. When
driven with an external clock, the device synchronizes
to the rising edge of SYNC.
An internal 250kHz ramp generator is compared
against the output of the error amplifier to generate the
PWM signal. The maximum amplitude of the ramp
(V
voltage and oscillator frequency changes. This causes
the V
voltage range of 4.5V to 40V (MAX5080) or 7.5V to 40V
(MAX5081) and the SYNC frequency range of 150kHz
to 350kHz.
The MAX5080/MAX5081 protects against an output short
circuit by utilizing hiccup-mode protection. In hiccup
mode, a series of sequential cycle-by-cycle current-limit
events will cause the part to shut down and restart with
RAMP
Oscillator/Synchronization Input (SYNC)
IN
PWM Comparator/Voltage Feedforward
/V
) automatically adjusts to compensate for input
RAMP
Output Short-Circuit Protection
to be a constant 10V/V across the input
______________________________________________________________________________________
Gate Drive Supply (DVREG)
Error Amplifier
(Hiccup Mode)
1A, 40V, MAXPower Step-Down
a soft-start sequence. This allows the device to operate
with a continuous output short circuit.
During normal operation, the current is monitored at the
drain of the internal power MOSFET. When the current
limit is exceeded, the internal power MOSFET turns off
until the next on-cycle and a counter increments. If the
counter counts seven consecutive current-limit events,
the device discharges the soft-start capacitor and
shuts down for 512 clock periods before restarting with
a soft-start sequence. Each time the power MOSFET
turns on and the device does not exceed the current
limit, the counter is reset.
The MAX5080/MAX5081 feature an integrated thermal-
overload protection. Thermal-overload protection limits
the total power dissipation in the device and protects it
in the event of an extended thermal fault condition.
When the die temperature exceeds +160°C, an internal
thermal sensor shuts down the part, turning off the
power MOSFET and allowing the IC to cool. After the
temperature falls by 20°C, the part will restart with a
soft-start sequence.
When the voltage at ON/OFF rises above 1.23V, the
MAX5080/MAX5081 turns on. Connect a resistive
divider from IN to ON/OFF to SGND to set the UVLO
threshold (see Figure 5). First select the ON/OFF to the
SGND resistor (R2) then calculate the resistor from IN
to ON/OFF (R1) using the following equation:
where V
turns on, V
than 600kΩ.
If the external UVLO divider is not used, connect
ON/OFF to IN directly. In this case, an internal under-
voltage lockout feature monitors the supply voltage at
IN and allows operation to start when IN rises above
4.1V (MAX5080) and 7.1V (MAX5081).
Connect a resistive divider from OUT to FB to SGND to
set the output voltage. First calculate the resistor from
OUT to FB using the guidelines in the Compensation
Design section. Once R3 is known, calculate R4 using
the following equation:
IN
ON/OFF
is the input voltage at which the converter
Setting the Undervoltage Lockout
DC-DC Converters
R
Applications Information
1
=
Thermal-Overload Protection
= 1.23V and R2 is chosen to be less
R
2
Setting the Output Voltage
×
⎡
⎢
⎢
⎣
V
ON/OFF
V
IN
−
1
⎤
⎥
⎥
⎦
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