PM6670ASTR STMicroelectronics, PM6670ASTR Datasheet - Page 25

• Manufacturer Part Number: PM6670ASTR
• Description: IC CTLR DDR2/3 MEM PS 24VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6670ASTR

• Applications: Memory, DDR2/DDR3 Regulator
• Current - Supply: 800µA
• Voltage - Supply: 4.5 V ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• For Use With: 497-8412 - BOARD EVAL PM6670AS DDR2/3497-8411 - BOARD EVAL PM6670S DDR2/3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6305-2; PM6670ATR

PM6670AS
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 14436 Rev 2
C
R
INT
INT
C
>
C
INT
=
FILT
Figure 30
2
2
⋅ π
⋅ π
>
⎛
⎜
⎝
=
2
f
CUT
f
⋅ π
SW
C
k
g
g
INT
m
f
m
Zout
⋅
−
.
C
C
1
f
⋅
q
Zout
INT
1 (
INT
⋅
V
−
+
Vr
OUT
⎞
⎟
⎠
⋅
) q
C
C
⋅
FILT
Vout
FILT
Vr
Device description
FILT
INT
CUT
that,
is given
must be
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