Power and Thermal Management ICs
Volume 8, Issue 6 YOUR SEMICONDUCTOR SOLUTIONS RESOURCE

On-Board Oscillators Synchronize Other Regulators to Reduce the Number of Beat Frequencies

Many systems are highly sensitive to noise and beat frequencies. When using switching regulators, this challenge is typically amplified by the fact that each regulator is running at a different frequency, thus generating a number of beat frequencies that are difficult to filter out. One approach to overcome this challenge is to run all switching regulators at the same switching frequency. However, to achieve this solution, all regulators need to be synchronized to the same oscillator. Rather than requiring placement of an oscillator circuit on a board, the oscillator output of ADI's ADP1828 dc-to-dc controller can be used to synchronize other controllers. The switching frequency is user programmable from 300 kHz to 600 kHz with a single resistor. The synchronization output frequency can be phase shifted 180° to reduce the size of input capacitors or it can be doubled with a pin setting to provide the 2× frequency that some switches require.

ADP1828

ADP1828 Features
Wide supply range: 3 V to 18 V
Oscillator frequency output to allow synchronization to other controllers
Accuracy over temperature: ±0.85%
Efficiency: up to 95%
Shutdown current: 15 µA

Part
Number
VIN
Range (V)
VOUT Adjustability
Options (V)
IOUT
Max (A)
Switch
Freq
Package Price
($U.S.)
ADP18211 3.7 to 5.5 0.6 to 0.85 VIN 20 600 kHz2 16-lead QSOP 1.35
ADP18221 3.7 to 5.5 0.6 to 0.85 VIN 20 600 kHz2 24-lead QSOP 1.40
ADP18281 3 to 18 0.6 to 0.85 VIN 20 600 kHz2 20-lead QSOP 1.50
ADP18291 3 to 18 0.6 to 17 20 600 kHz2 32-lead LFCSP 2.10
ADP18641 3.15 to 14 0.8 to VIN 5 580 kHz 6-lead TSOT 1.05
ADP21023 2.7 to 5.5 0.8 to 1.2, 1.2 to 1.5,
1.5 to 1.8, 2.5 to 3.3
0.6 3 MHz 8-lead LFCSP 1.47
ADP21053 2.7 to 5.5 0.8 to VIN 1 1.2 MHz 16-lead LFCSP 1.13
ADP21063 2.7 to 5.5 0.8 to VIN 1.5 1.2 MHz 16-lead LFCSP 1.25
ADP21073 2.7 to 5.5 0.8 to VIN 2 1.2 MHz 16-lead LFCSP 1.32
ADP30503 3.6 to 30 1.5 200 kHz 8-lead SOIC 1.78

1Step-down type.
2From 300 kHz to 600 kHz, synchronization up to 1 MHz.
3Buck type.

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