Datasheet HSMS-282x (Broadcom) - 7

bias differential amplifier matching HSMS-282P network Figure 17. Voltage Doubler Differential Detector. Figure 14. Fabrication of Avago Diode Pairs.
However, care must be taken to assure that the two refer‑ In high power applications, coupling of RF energy from ence diodes closely match the two detector diodes. One the detector diode to the reference diode can introduce possible configuration is given in Figure  16, using two error in the differential detector. The HSMS‑282K diode HSMS‑2825. Board space can be saved through the use of pair, in the six lead SOT‑363 package, has a copper bar the HSMS‑282P open bridge quad, as shown in Figure 17. between the diodes that adds 10 dB of additional isola‑ tion between them. As this part is manufactured in the While the differential detector works well over tempera‑ SOT‑363 package it also provides the benefit of being 40% ture, another design approach[3] works well for large signal smaller than larger SOT‑143 devices. The HSMS‑282K is il‑ detectors. See Figure 18 for the schematic and a physical lustrated in Figure 15—note that the ground connections layout of the circuit. In this design, the two 4.7 KΩ resis‑ must be made as close to the package as possible to min‑ tors and diode D2 act as a variable power divider, assuring imize stray inductance to ground. constant output voltage over temperature and improving output linearity.
detector diode PA Vbias RFin D1 4.7 K Vo 68 33 pF 4.7 K D2 68 33 pF HSMS-282K RF HSMS-2825 in reference diode or to differential amplifier HSMS-282K Figure 15. High Power Differential Detector. HSMS-282K Vo
The concept of the voltage doubler can be applied to the
4.7 K
differential detector, permitting twice the output voltage
Figure 18. Temperature Compensated Detector.
for a given input power (as well as improving input im‑ pedance and suppressing second harmonics). In certain applications, such as a dual‑band cellphone handset operating at both 900 and 1800  MHz, the sec‑
bias
ond harmonics generated in the power control output detector when the handset is working at 900 MHz can cause problems. A filter at the output can reduce unwant‑
differential
ed emissions at 1800 MHz in this case, but a lower cost
amplifier
solution is available[4]. Illustrated schematically in Figure 19, this circuit uses diode D2 and its associated passive components to cancel all even order harmonics at the de‑
HSMS-2825
tector’s RF input. Diodes D3 and D4 provide temperature compensation as described above. All four diodes are con‑
matching network HSMS-2825
tained in a single HSMS‑ 282R package, as illustrated in the layout shown in Figure 20.
Figure 16. Voltage Doubler Differential Detector.
Note 3. Hans Eriksson and Raymond W. Waugh, “A Temperature Compensated Linear Diode Detector,” to be published. 7