PM6670AS Datasheet, PDF (30/54 Pages) STMicroelectronics – Complete DDR2/3 memory power supplies controller

Device description
7.1.4
Mode-of-operation selection
Figure 33. MODE and DDRSEL multifunction pin configurations
PM6670AS
VDDQ
VDDQ
+5V
P_PM_M6₆6₆7₇0_0AS
+5V
PMM66667700AS
R9
R9
MODE
MODE
R8
R8
VREF
DDRSEL
DDRSEL
(a)
(b)
The PM6670AS has been designed to satisfy the widest range of applications involving
DDR2/3 memories, SSTL15-18 buses termination and I/O supplies for CPU/Chipset. The
device is provided with multilevel pins which allow the user to choose the appropriate
configuration. The MODE pin is used to firstly decide between fixed preset or adjustable
(user defined) output voltages.
When the MODE pin is connected to +5 V, the PM6670AS allows setting the VDDQ voltage
to 1.8 V or 1.5 V just forcing the DDRSEL multilevel pin to +5 V or to ground respectively
(see Figure 33a).
In this condition the Pulse-Skip feature is enabled. This device configuration is suitable for
standard DDR2/3 memory supply applications avoiding the need for an external, high
accuracy, divider for output voltage setting.
Applications requiring different output voltages can be managed by PM6670AS simply
setting the adjustable mode. If MODE pin voltage is higher than 4 V, the fixed output mode is
selected. Connecting an external divider to the MODE pin (Figure 33b), it is used as
negative input of the error amplifier and the output voltage is given by expression (21).
Equation 21
VDDQ _ADJ
=
0.9 ⋅
R8 + R9
R8
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