MAX1724 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX1724

1.5µA IQ, Step-Up DC-DC Converters in Thin SOT23-5

Maxim Integrated 

1.5µA IQ, Step-Up DC-DC Converters

in Thin SOT23-5

MAX1722

MAX1724

PDRV

TIMING

CIRCUIT

DAMP

NDRV

VOUT

VIN

OUT

BATT

P

DAMPING

SWITCH

LX

N

GND

Figure 4. Simplified Diagram of Damping Switch

1V/div

1V/div

1µs/div

Figure 5. LX Ringing Without Damping Switch (MAX1723)

1µs/div

Figure 6. LX Ringing With Damping Switch (MAX1722/MAX1724)

BATT/Damping Switch

(MAX1722/MAX1724)

The MAX1722/MAX1724 include an internal damping

switch (Figure 4) to minimize ringing at LX and reduce

EMI. When the energy in the inductor is insufficient to

supply current to the output, the capacitance and

inductance at LX form a resonant circuit that causes

ringing. The damping switch supplies a path to quickly

dissipate this energy, suppressing the ringing at LX.

This does not reduce the output ripple, but does

reduce EMI with minimal impact on efficiency. Figures

5 and 6 show the LX node voltage waveform without

and with the damping switch, respectively.

Design Procedure

Setting the Output Voltage

(MAX1722/MAX1723)

The output voltage can be adjusted from 2V to 5.5V

using external resistors R1 and R2 (Figure 7). Since FB

leakage is 20nA (max), select feedback resistor R1 in

the 100kΩ to 1MΩ range. Calculate R2 as follows:

R2

=

R1





VOUT

VFB



− 1

where VFB = 1.235V.

8 _______________________________________________________________________________________

Share Link: