A7115
AiT Semiconductor Inc.
DC-DC CONVERTER
www.ait-ic.com
1.5MHZ, 1.5A SYNCHRONOUS STEP-DOWN CONVERTER
Application Information
Setting the Output Voltage
Typical application above shows the basic application circuit with A7115. The external resistor sets the output
voltage according to the following equation:
R1=200KΩ for all outputs; R2=200kΩ for VOUT=1.2V, R2=300kΩ for VOUT=1.5V, R2=400kΩ for VOUT=1.8V,
and R2=633.3kΩ for VOUT=2.5V.
Inductor Selection
For most designs, the A7115 operates with inductors of 1μH to 4.7μH. Low inductance values are physically
smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived
from the following equation:
Where ΔIL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors
result in high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current
1500mA, or ΔIL=525mA.
For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor
is 2.2μH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the
50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 500mA), or minimal load regulation (but
some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor
should be at least equal to the maximum load current plus half the ripple current to prevent core saturation.
Table 1 lists some typical surface mount inductors that meet target applications for the A7115.
Table 1. Typical Surface Mount Inductors
Part Number
L (μH) Max DC Current (A) DCR (mΩ) Size LxWxH (mm)
2.2
3.3
4.7
2.0
3.3
4.7
3.0
2.6
3.4
3.3
2.6
2.1
28.7
35.6
19
Sumida CDRH5D16
Sumida CDRH8D28
5.8x5.8x1.8
8.3x8.3x3.0
23
Coiltronics SD53
29
5.2x5.2x3.0
39
REV1.0
- APR 2013 RELEASED, NOV 2014 UPDATED -
- 9 -
AITSEMI [ AiT Semiconductor ]
