Circuit Note

CN-0518

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Rev. 0 | 6 of 8

Figure 16. CN0518 Power Supply Architecture

SEPIC Converter

The LT8330 is a current-mode DC/DC converter capable of gener-

ating either positive or negative output voltages. It can be config-

ured as boost, SEPIC, or inverting converter consuming as low as

6 µA of quiescent current. Figure 17 shows the basic configuration

needed to set the LT8330 for a 5.6 V output.

Figure 17. LT8330 Configuration for a 5.6 V Output

The output voltage is programmed with resistor divider from the

output to the FBX pin of the LT8330. Equation 2 shows how to

calculate a desired output voltage with the user-defined resistor

values:

R1=R2  VOUT1.60−1

(2)

where:

VOUT is the desired output voltage in Volts.

R1, R2 are the user-defined resistor values.

For the required output voltage of 5.6 V, the equation results with

R1 = 590 kΩ and R2 = 232 kΩ.

Ultralow Noise Linear Regulator

The 5 V output from the ADM7150 is used to power the two

HMC376 LNAs. The ADM7150 is a low dropout linear regulator with

a typical noise of 1 µV rms from 100 Hz to 100 kHz for fixed output

voltage options and <1.7 nV/√Hz noise spectral density above 10

kHz.

The ADP150 is used to generate 3.3 V for powering the RF

detector and auto retry circuit. It is a high performance low dropout

linear regulator featuring an ultralow noise and ultra high PSSR

architecture for powering noise sensitive RF applications.

An ADM7170-2.5 LDO regulator is used to generate the supply

voltage required by the ADG901 RF switch. This device has an

input voltage range of 2.3 V to 6.5 V and a fixed output voltage

of 2.5 V. The ADM7170-2.5 only requires capacitors for proper

operation. Particularly, the ADM7170-2.5 is compatible to use small

decoupling capacitors of 4.7 µF on its input and output pins.

COMMON VARIATIONS

The ADL5523 can be used as an alternative low noise amplifier

for applications using the 915 MHz ISM band. This device offers a

slightly higher gain (S21) and a low noise figure at a cost of having

lower return losses (S11, S22), output third-order intercept, and 1

dB compression point.

The ADG902 can also be used as the RF switch, this device is

pin-compatible and shares the same specifications as the ADG901,

but it is a reflective switch and offers lower isolation loss.

Analog Devices, Inc. also offers a similar reference design for

receiver amplifiers operating in the 433.92 MHz, 2.4 GHz, and 5.8

GHz ISM bands. For more information, please refer to the CN0555,

CN0521, and CN0534 circuit notes.

If you are working in the 915 MHz ISM band and needs a transmit

signal chain solution, refer to the CN0522 reference design.

CIRCUIT EVALUATION AND TEST

This section describes the setup and procedure for the CN0518

circuit evaluation. For complete details, refer to the CN0518 User

Guide.

EQUIPMENT NEEDED

►

EVAL-CN0518-EBZ circuit evaluation board

►

Signal generator (Rohde & Schwarz® SMA100B)

►

Signal analyzer (Keysight® E5052B)

►

Vector network analyzer (Keysight N5242A PNA-X)

►

5 V, ≥0.5 A AC/DC power adapter with micro-USB cable

►

SMA cables

SETUP AND TEST

Figure 18 shows the functional block diagram for the S-Parameter

and noise figure test setup.

Figure 18. S-Parameter and Noise Figure Test Setup