Boost Module with True Shutdown

MAXM17225

www.maximintegrated.com

Maxim Integrated | 10

2.6

267

2.7

226

2.8

191

2.9

162

3.0

133

3.1

113

3.2

95.3

3.3

80.6

3.4

66.5

3.5

56.2

3.6

47.5

3.7

40.2

3.8

34

3.9

28

4.0

23.7

4.1

20

4.2

16.9

4.3

14

4.4

11.8

4.5

10

4.6

8.45

4.7

7.15

4.8

5.9

4.9

4.99

5.0

SHORT TO GND

PFM Control Scheme

The MAXM17225 utilizes a fixed on-time, current-limited, pulse-frequency-modulation (PFM) control scheme that allows

ultra-low quiescent current and high efficiency over a wide output current range. The inductor current is limited by the 1A

peak current limit or by the 300ns switch maximum on-time. During each switch ON cycle, either the maximum on-time

or the maximum current limit is reached before the off-time of the cycle begins. The MAXM17225 PFM control scheme

allows for both continuous-conduction mode (CCM) or discontinuous-conduction mode (DCM). When the error

comparator senses that the output voltage has fallen below the regulation threshold, another cycle begins. See the

MAXM17225 Simplified Block Diagram.

To increase efficiency, MAXM17225 incorporates a unique PFM control scheme wherein the converter auto-transitions

into different operating modes based on load current to be delivered. Ultra-low-power mode (ULPM) for very light load

so that it can more easily weather a future large load transient. In this mode, the converter switches at a rate of 17.5µs.

As load current demand rises to a 0.1-

dependent), the converter switches into LPM (low-power mode) wherein the converter always switches faster than 17.5µs.

Finally for high cu

rrents of the order of a few 10’s to 100’s of mA the converter operates in high-power mode (continuous-

conduction mode).