500mV to 5.5V Input, Ultrasonic

Boost Converter with Short-Circuit

Protection and True Shutdown

MAX18002

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Analog Devices | 11

Detailed Description

The MAX18002 is an ultrasonic boost converter with an input voltage range of 500mV to 5.5V ideal for IoT and wearable

applications. The start-up voltage required for the IC is about 1.8V (typical). The output voltage is adjustable between

2.5V and 5.5V (in steps of 100mV) using a single external resistor connected between RSEL and GND.

The MAX18002 operates in three modes; ultrasonic mode (USM), skip mode, and continuous conduction mode (CCM)

according to the load current. In USM, the switching frequency of the IC is kept above 22kHz even at light loads to stay

away from the audible frequency range. When VIN > VOUT, the part goes into pass-through mode where it regulates to

the VIN level and operates with a switching frequency of 29kHz (typical).

The part is equipped with a cycle-to-cycle switch current limit, thermal shutdown, and short-circuit protection to protect

the system and the device itself.

Output-Voltage Selection

The MAX18002 has a unique single resistor output selection method where the resistor connected between RSEL and

GND is used to select different output voltages from 2.5V to 5.5V (USM disabled for VOUT > 5V) in 100mV steps as

shown in Table 1. The advantages of using a single RSEL for output-voltage selection are as follows:

• Lower cost and smaller size, since only one resistor is needed versus the two resistor strings needed in typical

feedback connections.

• No power loss through feedback resistors during operation leading to higher efficiency.

• Allows customers to stock just one part in their inventory system and use it in multiple projects with different output

voltages just by changing a single standard 1% resistor.

Table 1. RSEL Selection Table

OUTPUT VOLTAGE (V)

RSEL (kΩ)**

2.5

768

2.6

634

2.7

536

2.8

452

2.9

383

3.0

324

3.1

267

3.2

226

3.3

191

3.4

162

3.5

133

3.6

113

3.7

95.3

3.8

80.6

3.9

66.5

4.0

56.2

4.1

47.5

4.2

40.2

4.3

34

4.4

28

4.5

23.7

4.6

20

4.7

16.9