One occurrence of the runaway-current limit triggers a

hiccup mode. In addition, if due to a fault condition, output

voltage drops to 68% (typ) of its nominal value any time

after soft-start is complete, hiccup mode is triggered.

The device has two modes of operation under overload

conditions – hiccup mode and latchoff mode. In hiccup

mode, the converter is protected by suspending switching

for a hiccup timeout period of 32,768 clock cycles. Once

the hiccup-timeout period expires, soft-start is attempted

again. In latchoff mode, the converter does not attempt

to soft-start the output after a timeout period. The power

supply to the device needs to be cycled to turn the part on

again in latchoff mode of operation. A resistor connected

from DL to SGND sets the peak and runaway current

limits and the operating mode during overload conditions.

RESET Output

The device includes a RESET comparator to monitor

the status of the output voltage. The open-drain RESET

output requires an external pullup resistor. RESET goes

high (high impedance) 1024 switching cycles after the

regulator output increases above 95.6% of the designed

nominal regulated voltage. RESET goes low when the

regulator output voltage drops to below 92.2% of the set

nominal output regulated voltage. RESET also goes low

during thermal shutdown.

Prebiased Output

When the device starts into a prebiased output, both the

high-side and the low-side switches are turned off so the

converter does not sink current from the output. High-

side and low-side switches do not start switching until

the PWM comparator commands the first PWM pulse, at

which point switching commences. The output voltage is

then smoothly ramped up to the target value in alignment

with the internal reference.

Thermal Shutdown Protection

Thermal-shutdown protection limits total power dissipation

in the MAX17536. When the junction temperature of the

device exceeds +165°C, an on-chip thermal sensor shuts

down the device, allowing it to cool. The MAX17536 turns

ON with soft-start after the junction temperature reduces

by 10°C. Carefully evaluate the total power dissipation

(see the Power Dissipation section) to avoid unwanted

triggering of the thermal shutdown in normal operation.

Applications Information

Input Capacitor Selection

The input-filter capacitor reduces peak currents drawn

from the power source and reduces noise and voltage

ripple on the input caused by the circuit’s switching.

defined by the following equation:

×

=

×

OUT

IN

OUT

RMS

OUT(MAX)

IN

V

(V - V

)

II

V

a maximum value when the input voltage equals twice

Choose an input capacitor that exhibits less than +10°C

temperature rise at the RMS input current for optimal

long-termreliability.Uselow-ESRceramiccapacitorswith

highripple-currentcapabilityattheinput.X7Rcapacitors

are recommended in industrial applications for their

temperature stability. Calculate the input capacitance

using the following equation:

××

=

η×

× ∆

OUT(MAX)

IN

SW

IN

I

D (1- D)

C

fV

voltage ripple, and E is the efficiency.

In applications where the source is located distant from

the device input, an electrolytic capacitor should be

added in parallel to the ceramic capacitor to provide

necessary damping for potential oscillations caused by

the inductance of the longer input power path and input

ceramic capacitor.

Inductor Selection

Three key inductor parameters must be specified for

operation with the MAX17536: inductance value (L),

determine the inductor value as follows:

OUT

SW

V

L

2.2 f

=

×

RESISTANCE

(kΩ)

PEAK

CURRENT

LIMIT (A)

RUNAWAY

CURRENT

LIMIT (A)

FAULT

OPERATING

MODE

Open

6.5

7.5

Hiccup

174

6.5

7.5

Latchoff

61.9

5

6

Hiccup

26.1

5

6

Latchoff

Maxim Integrated │ 14

MAX17536

4.5V to 60V, 4A, High-Efficiency, Synchronous

Step-Down DC-DC Converter

with Internal Compensation

www.maximintegrated.com