ADL5511 VRMS and VENV Response Time to VPOS Turn-On

Document created by enash Employee on Oct 21, 2014Last modified by enash Employee on Oct 22, 2014
Version 3Show Document
  • View in full screen mode

Q. The datasheet for ADL5511 shows the output response time when the ENBL pin is pulsed. What do the VRMS and VENV response times look like when VPOS is pulsed on and off.

 

A. The attached plots show the response of VRMS when VPOS is pulsed for different values of CRMS (i.e. open, 10nF, 100nF and 4.7 nF). As you can see, the VRMS rise time following the turn on of VPOS has a strong dependency on the value of CRMS. With CRMS set to 0.1uF, there is are slight rise and fall time glitches. These glitches never exceed the settled value of VRMS.

 

VRMS Pin 1dBm Crms 0.1uF Cdecl 0.1uF.bmp

VRMS response to turn on of VPOS, CRMS = 0.1uF, Cdecl = 0.1uF, Pin = +1dBm

 

Increasing the value of CRMS lengthens the turn on time.

VRSM Pin 1 dBm Crms 4.7uF Cdecl 0.1uF.bmp

VRMS response to turn on of VPOS, CRMS = 4.7 uF, Cdecl = 0.1uF, Pin = +1dBm

 

Decreasing the value of CRMS shortens the rise time with the rise and fall time glitches maintaining their character.

 

VRMS Pin 1dBm Crms 10nF Cdecl 0.1uf.bmp

VRMS response to turn on of VPOS, CRMS = 10 nF, Cdecl = 0.1uF, Pin = +1dBm

 

Removing CRMS changes the shape of the VRMS response when VPOS is pulsed. This results in a sharp rising-side glitch.  This is not a recommended mode of operation since without an rms averaging capacitor (CRMS) present, there is no correct rms computation taking place.

VRMS Pin 1dBm Crms open Cdecl 0.1uF.bmp

VRMS response to turn on of VPOS, CRMS = open, Cdecl = 0.1uF, Pin = +1dBm

 

With the RF input turned off, the following response was observed where VRMS exhibits small positive and negative glitches (approx. +200mV and -150mV)  as VPOS is turned on an off.

VRMS Pin off Crms 0.1uF Cdecl 0.1uf.bmp

VRMS response to turn on of VPOS, CRMS = 0.1uF, Cdecl = 0.1uF, Pin = off

 

The next plot shows the response of VENV when VPOS is pulsed. Note that the value of CRMS has no effect on the rise time of VENV

 

VENV Pin 1 dBm Cdecl 0.1uF.bmp

VENV response to turn on of VPOS, CRMS = Not Applicable, Cdecl = 0.1uF, Pin = +1dBm

 

With RFIN turned off, VENV jumps to its 1.1 V pedestal level when VPOS is pulsed on. This is shown in the last plot.

VENV Pin off Crms NA Cdecl 0.1uF.bmp

VENV response to turn on of VPOS, CRMS = Not Applicable, Cdecl = 0.1uF, Pin = off

 

For all of these measurements (except where noted) a continuous input power level of +1dBm was applied. The rise time of VPOS is affected by the presence of the power supply decoupling capacitors (0.1uF and 100pF).

Attachments

    Outcomes