Limited Current Circuit for PA

limited current circuit

hi,I am designing a PCMCI EDGE wireless card used in notebook computer .and now i have to stop advancing for a problem. you know , notebook computer 's PCMCIA interface is power limited,which is limited in 3.3W output. but when the EDGE card works in GSM pcl 5 ,it needs at least 34dBm (32.5+1.5 IL),or 2.5W, but considering the whole system's demand ,we now only have 1.8W to it, so we adapt one big capacitance (100mF) to compensate .but the result is not as we imagine ,the voltage (we use 3.3v ) drops 500mv still( this lead the system's unsteable) or to say,the capacitance doesn't work!!, why? the power line we supply is :3.3v(notebook computer)-->DC/DC (TPS61030 TI, 3.8v)--->LDO( R1173D001D RICHON 3.6V)--->PA

and now ,i'd like to design a current limited circuit between DC/DC and PA to let capacitance work ,how could i do? or does anybody here know how to use LDO ,for example R1173D001D,realize this function ??

thanks advance!!

limited corrent circuits

Better than using only one big capacitor to avoid the 1A current limit of PCMCIA, is to use multiple tantalum capacitors in parallel. That circuit gives lower ESR and better performance under multislot operation.

**broken link removed**

Beware that in EDGE mode class E2 the maximum output power is 27dBm (850/900MHz) and 26dBm (1800/1900MHz). This would help to get lower overall power consumption in multislot operation compared to standard GSM.

tps61030 problem

thank u very much for your reply,could u give me a idea about how to make the capacitance (or those tantalum)work?

i have read through the paper you offered to me ,but i am still confused about my question----i have placed many tantalum capacitor for PA bulk capacitance.but they seems doesn't work indeed! ! i know that my power supply have problem somewhere ,but where? .....waiting for your answer eagerly.....

i plan to place a limited current circuit between DC/DC and PA .....

ltc3428

There is no magic how to put a few capacitors in parallel. They should work fine if you have a proper layout and grounding.

A good DC/DC converter that I used successfully for this application is the dual-phase LTC3428.

anybody?