PM6670ASTR STMicroelectronics, PM6670ASTR Datasheet - Page 21

• 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
The duty-cycle of the buck converter is, in steady-state conditions, given by
Equation 2
The switching frequency is thus calculated as
Equation 3
where
Equation 4a
Equation 4b
Referring to the typical application schematic (figures on cover page and
final expression is then:
Equation 5
Even if the switching frequency is theoretically independent from battery and output
voltages, parasitic parameters involved in power path (like MOSFETs' on-resistance and
inductor's DCR) introduce voltage drops responsible for slight dependence on load current.
In addition, the internal delay is due to a small dependence on input voltage. The
PM6670AS switching frequency can be set by an external divider connected to the VOSC
pin.
f
SW
Doc ID 14436 Rev 2
=
f
SW
T
D
ON
=
K
α
=
α
OSC
OSC
α
K
OSC
OUT
D
OSC
=
V
=
V
OUT
=
=
V
--------------
IN
R
V
V
V
OUT
1
V
-------------- -
--------------
V
OSC
V
SNS
IN
R
V
+
OSC
OUT
SNS
2
IN
R
2
=
⋅
α
α
K
OSC
OUT
OSC
1
⋅
K
OSC
1
Device description
Figure 27
), the
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