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Evaluates: MAX17521 in 3.3V and 5V

Output-Voltage Application

MAX17521 Evaluation Kit

Detailed Description

The MAX17521 EV kit provides a proven design to evaluate

the MAX17521 high-efficiency, high-voltage, dual synchronous

step-down DC-DC converter. The EV kit generates 3.3V and

5V, at load currents up to 1A, from a 7V to 60V input supply.

The EV kit features a switching-frequency selector pin

and individual mode-of-operation selector pins, enable/

undervoltage-lockout (EN/UVLO) pins, programmable

soft-start pins, and open-drain RESET signals for each

output.

Soft-Start Input (SS)

The device implements adjustable soft-start operation to

reduce inrush current. Capacitors connected from the SS pins

to SGND programs the soft-start time for the corresponding

output voltage. The selected output capacitance (CSEL) and

the output voltage (VOUT) determine the minimum required

soft-start capacitor as follows:

CSS ≥ 56 x 10-6 x CSEL x VOUT

The soft-start time (tSS) is related to the capacitor

connected at SS (CSS) by the following equation:

tSS = CSS/(5.55 x 10-6)

For example, to program a 1ms soft-start time, a 5.6nF

capacitor should be connected from the SS pin to SGND.

Regulator Enable/Undervoltage-Lockout Level

(EN/UVLO1, EN/UVLO2)

The device offers an adjustable input undervoltage-

lockout level for each output. Set the voltage at which

each converter turns on with a resistive voltage-divider

connected from VIN to SGND (viewable

here). Connect

the center node of the divider to EN/UVLO pin.

Choose RTOP to be 3.3MΩ, and then calculate RBOTTOM

as:

TOP

BOTTOM

INU

1.218

−

Where VINU is the input voltage at which a particular

converter is required to turn on. Install a shunt across pins

1-2 on J1 and J2 to enable the EV kit’s outputs. See Table 1

and Table 2 for proper jumper settings.

Table 1. Regulator Enable (EN/UVLO1)

Description (J1)

*Default position.

Table 2. Regulator Enable (EN/UVLO2)

Description (J2)

SHUNT

POSITION

EN/UVLO1 PIN

MAX17521_ OUTPUT1

1-2*

Connected to VIN1

Enabled

Not

installed

Connected to the center

node of resistor-divider

R3 and R4

Enabled, UVLO level set

through the R3 and R4

resistors

2-3

Connected to SGND

Disabled

SHUNT

POSITION

EN/UVLO2 PIN

MAX17521_ OUTPUT2

1-2*

Connected to VIN2

Enabled

Not

installed

Connected to the center

node of resistor-divider

R11 and R12

Enabled, UVLO level set

through the R11 and R12

resistors

2-3

Connected to SGND

Disabled

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