PM6670S STMicroelectronics, PM6670S Datasheet - Page 26

• Manufacturer Part Number: PM6670S
• Description: IC CTLR DDR2/3 MEM PS VFQFPN-24
• Manufacturer: STMicroelectronics

Specifications of PM6670S

• 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: 497-8411 - BOARD EVAL PM6670S DDR2/3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Device description
26/54
Figure 32. “Virtual-ESR” network
The ripple on the COMP pin is the sum of the output voltage ripple and the triangular ripple
generated by the Virtual-ESR network. In fact the Virtual-ESR Network behaves like a
another equivalent series resistor R
A good trade-off is to design the network in order to achieve an RVESR given by:
Equation 11
where ΔI
greater than approximately 20 mV.
The new closed-loop gain depends on C
that:
Equation 12
where:
Equation 13
and:
T NODE
VOLTAGE
L
is the inductor current ripple and V
ΔV
1
OUTPUT
VOLTAGE
R
R
ΔV
T
COMP PIN
VOLTAGE
t
Doc ID 14432 Rev 4
V
REF
C
R
R
C
R
R
1
R
1
INT
INT
VESR
VESR
C
f
t
Z
INT
C
=
C
INT
.
INT
INT
2
=
>
⋅ π
V
. In order to ensure stability it must be verified
2
RIPPLE
g
⋅ π
C
RIPPLE
COMP
Δ
COMP
ESR
ESR
C
C
t
m
out
VSNS
I
f
L
ΔV
OUT
OUT
1
Z
C
C
⋅
2
FILT
⋅
FILT
R
Vout
−
Vr
TOT
is the total ripple at the T node, chosen
ESR
I=g
m
Vr
Vr
(V
1
-Vr)
R
R
Fb2
Fb2
g
g
V
V
m
m
1
1
+
V
V
REF
REF
R
R
Fb1
Fb1
+
-
Comparator
Comparator
PWM
PWM
PM6670S