STEVAL-ISA051V2 STMicroelectronics, STEVAL-ISA051V2 Datasheet - Page 30

• Manufacturer Part Number: STEVAL-ISA051V2
• Description: BOARD EVAL PM6670AS DDR2/3
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA051V2

• Design Resources: STEVAL-ISA051V2 Gerber Files STEVAL-ISA051V2 Schematic STEVAL-ISA051V2 Bill of Material
• Main Purpose: Special Purpose DC/DC, DDR Memory Supply
• Outputs And Type: 4, Non-Isolated
• Voltage - Output: 1.5V, 1.8V
• Voltage - Input: 4.5 ~ 36V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6670A
• Input Voltage: 4.5 V to 36 V
• Output Voltage: 1.8 V, 1.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6670AS
• Kit Application Type: Power Management
• Application Sub Type: DDR2/3 Memory Power Supply Controller
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6670AS
• Other names: 497-8412

Device description
7.1.5
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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
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 (
negative input of the error amplifier and the output voltage is given by expression (21).
Equation 21
VDDQ output voltage can be set in the range from 0.9 V to 2.6 V. Adjustable mode
automatically switches DDRSEL pin to become the power saving algorithm selector: if tied
to +5 V, the forced-PWM (fixed frequency) control is performed. If grounded or connected to
VREF pin (1.237 V reference voltage), the pulse-skip or non-audible pulse-skip modes are
respectively selected.
Table 8.
Current sensing and current limit
The PM6670AS switching controller uses a valley current sensing algorithm to properly
handle the current limit protection and the inductor current zero-crossing information. The
current is sensed during the conduction time of the low-side MOSFET. The current sensing
element is the on-resistance of the low-side switch. The sensing scheme is visible in
Figure 34
V
V
Figure 33
MODE
MODE
Mode
.
> 4.3 V
< 3.7 V
Mode-of-operation settings summary
a).
1 V < V
1V < V
V
V
V
DDRSEL
DDRSEL
DDRSEL
DDRSEL
DDRSEL
DDRSEL
<0.5 V
Doc ID 14436 Rev 2
VDDQ
> 4.2 V
> 4.2 V
< 0.5 V
< 3.5 V
< 3.5 V
ADJ
=
0
9 .
VDDQ
1.8 V
1.5 V
ADJ
⋅
R
8
R
+
8
R
9
Figure 33
Non-Audible Pulse-skip
Operating mode
Forced-PWM
b), it is used as
Pulse-Skip
Pulse-Skip
PM6670AS