POWER
Figure 3. With minimal output capacitors (2 × 4.7μF ceramics), the LTM8074 provides a quick transient response (12VIN, 3.3VOUT).
operating conditions with a broad range of output capacitors.
Through the use of just one external resistor for setting the desired output voltage, the type variability is reduced and a certain amount of flexibility is provided for the application. If soft-start is not required, no capacitor has to be connected to the corresponding pin. All these capabilities make voltage conversion possible in an extremely small board area. With just the 4mm × 4mm edge length of the LTM8074 and minimal external wiring, the complete power supply unit can be operated on only approximately 8mm × 8mm of board area with an input voltage of up to 40V and a permissible output current of up to 1.2A. Figure 5 shows an example layout with the minimal number of necessary external components.
The LTM8074 is a 1.2A, 40VIN µModule step- down regulator in a tiny 4mm × 4mm ×
Figure 4. The LTM8074 with a VIN of up to 40V and an output current of 1.2A in a space of just 4mm × 4mm.
1.82mm, 0.65mm pitch BGA package. Its total solution size is 60mm2 for 3.2VIN to 40VIN, 3.3VOUT requiring only two 0805 capacitors and two 0603 resistors. The low profile and light-weight (0.08g) package permits the device to be assembled on the backside of a PCB where the topside is often very densely populated. Its Silent Switcher architecture minimises EMI emissions, enabling the LTM8074 to pass CISPR22 Class B, and reduce the possibility of EMC susceptibility to other sensitive circuits. It is not usually possible to integrate all of the external components. There is a simple reason for this. If, for example, certain settings such as the switching frequency or the soft-start time should be adjustable, the circuit must be told what to do. This could be done in a digital manner. However, this would mean using a microcontroller and non-volatile memory with the associated costs in the system. A common way of
getting around this is to use external passive components for making these settings. Input and output capacitors are often integrated into the power module, but also sometimes externally required. Figure 4 shows a circuit with the LTM8074 from Analog Devices.
For small power supplies, it is very important to offer an especially high conversion efficiency, otherwise there could potentially be problems with heat dissipation.
The LTM8074, with an extremely compact size, is an ideal choice for this. Through its integrated Silent Switcher technology, it can even be used in circuits that are especially noise sensitive and are usually supplied by linear regulators.
Highly integrated power modules are not only suitable for simplifying the design of switched-mode power supplies, but are also useful for enabling efficient voltage conversion in an extremely small space. The key performance characteristics of ADI µModule devices are: •
• • •
• • • •
Lower noise (ultralow noise and Silent Switcher devices) Ultrathin packages
6-sided efficient cooling (CoP)
Precision VOUT regulation over line, load, and temperature Extreme reliability testing Minimum ground loops
Multiple output on substrate Extreme temperature testing
Figure 5. Example layout on a board area of approximately 8mm × 8mm.
Frederik Dostal, Field Applications Engineer, Analog Devices
www.analog.com
MAY 2024 | ELECTRONICS FOR ENGINEERS 37
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