Evaluating Other Dynamic Output Voltages

The EV kit output is preset to 1.05V/1.5V. However, the

output voltage can also be adjusted between 0 and 2V

(FB = OUT) by selecting R1, R2, and R3 values. The

MAX8792 regulates FB to the voltage set at REFIN. By

changing the voltage at REFIN, the MAX8792 can be

used in applications that require dynamic output volt-

age changes between two set points. Using the exter-

nal GATE signal, a resistor can be switched in and out

of the REFIN resistor-divider, changing the voltage at

REFIN. A logic-high on GATE turns on the external

n-channel MOSFET, forcing N3’s drain to a low-imped-

ance state. A logic-low on GATE disables the n-channel

MOSFET, so N3’s drain is high impedance. The two

output voltages (FB = OUT) are determined by the fol-

lowing equations:

Resistive Voltage-Divider at FB

Connecting FB to a resistive voltage-divider allows

for output voltages above the reference voltage (0 to

resistor R10 with a 10k

Ω ±1% resistor and replace R9

with the following equation:

The switching-frequency setting input should then be

according to the following equations:

under normal operating conditions. Refer to the

MAX8792 data sheet for selection of output capacitor

and inductor values for output voltages greater than 2V.

TC

R

k

V

V

T

f

SW

TON

TON

FB

OUT

SW

SW

=+

()

⎛

⎝⎜

⎞

⎠⎟

=

65

1

.

Ω

VV

R

R

OUT

FB

=+

⎛

⎝⎜

⎞

⎠⎟

1

9

10

V

R

RR

V

V

RR

RR

R

V

OUT LOW

REF

OUT HIGH

REF

()

()

=

+

⎛

⎝⎜

⎞

⎠⎟

=

+

++

⎛

⎝⎜

⎞

⎠⎟

2

12

23

12

3

MAX8792 Evaluation Kit

4

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