Here are a few lines of code which will put the CC2520 in the so-called Low-Power RX mode, reducing RX power consumption to 18.3 mA, a value comparable top that of the CC2420. Please see the data sheet, section 5.10 for more information about the CC2520 Low Power RX mode. The function used in this example are taken from the CC2520 SW examples.
/***********************************************************************************
* @fn stCurRxLowCurrent
*
* @brief This function puts the radio in low current RX mode.
*
* @param none
*
* @return none
*/
static void stCurRxLowCurrent(void)
{
CC2520_MEMWR8(CC2520_RXCTRL,0x33);
CC2520_MEMWR8(CC2520_FSCTRL,0x12);
CC2520_MEMWR8(CC2520_AGCCTRL2,0xEB);
CC2520_INS_STROBE(CC2520_INS_SRXON);
}