LMX2594: lmx 2594 output freq unaccuracy

zheng caiyu

Prodigy 20 points

Part Number: LMX2594
Other Parts Discussed in Thread: LMX2592,

Tool/software:

hello everyone.

I have design a pcb board use lmx2592 to generate signal.

Is lmx2592 pin compatiable with lmx2594??

In same PCB,the output frequency of LMX2592 is accurate.But the output freq of LMX2594 have bigfrequency deviations.

and the deviations is not fixed.

for example

the loop filter parameter is the same as lmx2592 which is work fine.

here is my test code:

#include "lmx2594.h"


#include "stm32f0xx.h"

unsigned int LMX2594_Reg[113]=
{
	0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0001,
0x0001,
0x0064,
0xFFFF,
0x3FFF,
0x0011,
0x0064,
0x0000,
0xB000,
0x0888,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0000,
0x0001,
0x0000,
0x0000,
0x0001,
0x0000,
0x0200,
0x00BF,
0x0000,
0x000C,
0x0A40,
0x0000,
0x003F,
0x0001,
0x0081,
0xC350,
0x0000,
0x03E8,
0x0000,
0x01F4,
0x0000,
0x1388,
0x0000,
0x0322,
0x00A8,
0x0000,
0x0001,
0x8001,
0x0020,
0x0000,
0x0000,
0x0000,
0x0000,
0x0820,
0x0080,
0x0000,
0x4180,
0x0300,
0x0300,
0x07FC,
0xC0DF,
0x0A23,
0x8000,
0x0005,
0x0000,
0x0000,
0x8001,
0x53E2,
0x8304,
0x1F40,
0x0004,
0x0000,
0x1E21,
0x0393,
0x43EC,
0x318C,
0x318C,
0x0488,
0x0002,
0x0DB0,
0x0624,
0x071A,
0x007C,
0x0001,
0x0401,
0xC848,
0x27B7,
0x0064,
0x0110,
0x0080,
0x064F,
0x1E40,
0x4000,
0x5001,
0x0148,
0x10D8,
0x1604,
0x2000,
0x40B2,
0xC802,
0x00C8,
0x0A43,
0x0642,
0x0500,
0x0808,
0x2478,

};
static void DELAY_Nop(uint32_t num)
 {
 	while(num--)
	{
 		__NOP();
	}
 }


void LMX2594_Init()
{
	unsigned int y=0,j;
	
	
	LmxWrite(0,0x0002);//soft reset
	DELAY_Nop(500);
	LmxWrite(0,0x0000);//cancel reset	
	DELAY_Nop(500);
	DELAY_Nop(500);
	DELAY_Nop(500);
	
//	VCO_Caliberation();
	for(y=113;y>6;y--)
	{
		LmxWrite(113-y,LMX2594_Reg[y-1]);
	DELAY_Nop(100);
		j=lmxRead(113-y);

		/*while(j!=LMX2594_Reg[y-1])
		{
			//WDT_CONTR=0x25;//?????
			LMX2594_TXData(113-y,LMX2594_Reg[y-1]);
			j=LMX2594_RXData(113-y);
		}
		//WDT_CONTR|= 0x10;//??*/	
	}
//	WDT_CONTR= 0x00;//????
	DELAY_Nop(5000);
 //delay_ms(10);  //??10ms

 //lmx.R0.FCAL_EN=1;   //??FCAL_EN=1????????R0,???VCO?????????
 LmxWrite(0,0x2478);//lmx_wr(0,lmx.R0.REG0);
	
}

any suggestion please

3 months ago

0 Noel Fung 3 months ago

TI__Guru** 107450 points

Hi Zhang,

Yes, they are pin compatible.

software are not 100% compatible, you can use TICS Pro to generate the register settings and apply it in your software. Suggested programming sequence:

1. Vcc power

2. program RESET = 1

3. program all the registers in descending order, the last one to program is R0 (with FCAL_EN=1).

4. Wait 10ms and program R0 again (this step is usually not needed. this step is required only if it is unlock after step 3).

Your LMX2594 configuration looks good.

Since the PLL configuration are different with different devices, can you confirm the same loop filter can be applied to these devices? You can use PLL Sim (www.ti.com/.../PLLATINUMSIM-SW) to design the loop filter.

0 Noel Fung 3 months ago in reply to Noel Fung

TI__Guru** 107450 points

one more thing, suggest use below default setting.

Clock & timing

Clock & timing forum

LMX2594: lmx 2594 output freq unaccuracy