There are various types of DDR RAM available. The main difference is power and the second is speed. Each DDR RAM requires three levels of voltage VDD for RAM chips, VTT called reference voltage is always half to VDD voltage and last SPD voltage. There is one small chip in very every RAM called SPD chip which stores DDR capacity, speed, and other information time is called BIOS to RAM.
DDR RAM Test Voltages
Below are testing voltages for DDR RAMs
DDR1 Test Voltage
DDR1 produces 2.5 volt as VDD. Secondly, its VTT will be 1.25 volt. Lastly, its SPD is always 3.3 volt.
DDR2 Test Voltage
DDR2 produces 1.8 volt as VDD. Secondly, its VTT will be 0.9 volt. Lastly, its SPD is always 3.3 volt.
DDR3 Test Voltage
DDR3 produces 1.5 volt as VDD. Secondly, its VTT will be 0.75 volt. Lastly, its SPD is always 3.3 volt.
DDR3L Test Voltage
DDR3L produces 1.35 volt as VDD. Secondly, its VTT will be 0.65 volt. Lastly, its SPD is always 3.3 volt.
DDR4 Test Voltage
DDR1 produces 1.2 volt as VDD. Secondly, its VTT will be 0.6 volt. Lastly, its SPD is always 3.3 volt.
DDR RAM Test Points
| Signal | Pin Number |
|---|---|
| VREF | 1 |
| CLOCK | 101, 102, 103, 104 |
| CS | 114 |
| SM DATA, CLOCK | 200, 202 |
| DRAM_RST | 30 |
| WRITE | 113 |
| Signal | Pin Number |
|---|---|
| VDD = 1.2 volt | 33, 75, 111, 129, 135, 159, 163, 12, 54, 72, 96 |
| VTT = 0.6 volt | 258 |
| SPD = 3.3 volt | 255 |
| VPP = 2.5 volt | 257, 259 |
| DRAMRST | 108 |
| SMBUS | 254, 253 |
It is very important to know RAM voltages in laptop repairing. By judging RAM voltages on test points, we conclude that the RAM section is working properly or getting blocked by something.
After the RAM section, we go to the repair of the VRM section in the laptop repairing sequence. You can see a laptop repairing career consists of finding out and troubleshooting these sections.
You can also look at DDR memory comparison and have an overview of DDR RAMS.
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