STEVAL-ISA051V1 STMicroelectronics, STEVAL-ISA051V1 Datasheet - Page 25

• Manufacturer Part Number: STEVAL-ISA051V1
• Description: BOARD EVAL PM6670S DDR2/3
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA051V1

• Design Resources: STEVAL-ISA051V1 Gerber Files STEVAL-ISA051V1 Schematic STEVAL-ISA051V1 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 ~ 28V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6670
• Input Voltage: 4.5 V to 28 V
• Output Voltage: 1.8 V, 1.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6670S
• 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: PM6670S
• Other names: 497-8411

PM6670S
The design of the external feedback network depends on the output voltage ripple. If the
ripple is higher than approximately 20 mV, the correct CINT capacitor is usually enough to
keep the loop stable. The stability of the system depends firstly on the output capacitor zero
frequency.
The following condition must be satisfied:
Equation 6
where k is a fixed design parameter (k > 3). It determines the minimum integrator capacitor
value:
Equation 7
where gm = 50 μs is the integrator trans conductance.
In order to ensure stability it must be also verified that:
Equation 8
If the ripple on the COMP pin is greater than the integrator 150 mV, the auxiliary capacitor
C
by:
Equation 9
In order to reduce the noise on the COMP pin, it is possible to add a resistor R
together with CINT and C
much greater (10 or more times) than the switching frequency:
Equation 10
If the ripple is very small (lower than approximately 20 mV), a different compensation
network, called “Virtual-ESR” network, is needed. This additional circuit generates a
triangular ripple that is added to the output voltage ripple at the input of the integrator. The
complete control scheme is shown in
FILT
can be added. If q is the desired attenuation factor of the output ripple, C
FILT
, becomes a low pass filter. The cutoff frequency f
Doc ID 14432 Rev 4
C
f
R
SW
INT
INT
C
>
>
C
INT
=
k
FILT
Figure 32
2
2
⋅
⋅ π
f
⋅ π
>
Zout
⎛
⎜
⎝
=
2
f
CUT
f
⋅ π
SW
C
=
k
g
g
INT
m
f
m
2
Zout
⋅
−
.
⋅ π
C
C
1
f
⋅
q
Zout
INT
1 (
INT
C
⋅
V
−
out
k
+
Vr
OUT
⎞
⎟
⎠
⋅
) q
C
C
⋅
⋅
ESR
FILT
Vout
FILT
Vr
Device description
FILT
INT
CUT
that,
is given
must be
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