A7566
AiT Semiconductor Inc.
www.ait-ic.com
DC-DC CONVERTER BOOST(STEP-UP)
1.2MHz, MICROPOWER SYNCHRONOUS
Table2. Typical Surface Mount Inductors
Part Number
Sumida
L(μH)
Max DCR (mΩ)
Rated D.C. Current (A)
Size WxLxH (mm)
4.3x4.8x3.5
4.7
10
108.7
182
72
1.15
1.04
1.32
1.17
1.12
1.00
1.87
1.51
1.33
CR43
4.7
5.6
6.8
10
Sumida
101
109
128
45
5.0x5.0x3.0
5.0x5.0x3.0
CDRH4D28
4.7
6.8
10
Toko
68
D53LC
90
Output Capacitor Selection: The output capacitor is required to keep the output voltage ripple small and to
ensure regulation loop stability. A 2.2μF to 10μF output capacitor is sufficient for most applications. If output
capacitor is larger than 10μF, a phase lead capacitor must be included to maintain enough phase margin. The
output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R
dielectrics are recommended due to their low ESR and high ripple current ratings.
Input Capacitor Selection: The input capacitor reduces the surge current drawn from the input and switching
noise from the device. A minimum 4.7µF input capacitor is needed for most applications. The input capacitor
impedance at the switching frequency should be less than input source impedance to prevent high frequency
switching current passing to the input. A low ESR input capacitor sized for maximum RMS current must be
used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR
and small temperature coefficients.
PCB Layout Guidance
The A7566 operates at 1.2MHz typically. This is a considerably high frequency for dc-dc converters. In such
case PCB layout is important to guarantee satisfactory performance. It is recommended to make traces of the
power loop, especially where switching node is involved as short and wide as possible. First of all, the
inductor, input and output capacitor should be close to the device. Feedback and shut down circuit should
avoid the proximity of large AC signals, e.g. the power inductor and switching nodes. The optional rectifier
diode (D1) can improve efficiency and alleviate the stress on the integrated MOSFET. The diode should also
be close to the inductor and the chip to form the shortest possible switching loop. Large and integral multi
layer ground planes are ideal for high power applications. Large area of copper has lower resistance and
helps to dissipate heat on the device. The converter’s ground should join the system ground to which it
supplies power at one point only.
REV1.1
- APR 2015 RELEASE, MAR 2018 UPDATED -
- 9 -
AITSEMI [ AiT Semiconductor ]
