参数资料
型号: PM6670STR
厂商: STMICROELECTRONICS
元件分类: 稳压器
英文描述: 3 A SWITCHING CONTROLLER, QCC24
封装: 4 X 4 MM, LEAD FREE, VFQFPN-24
文件页数: 15/54页
文件大小: 742K
代理商: PM6670STR
Device description
PM6670S
22/54
Doc ID 14432 Rev 4
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 Figure 29), the
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 PM6670S
switching frequency can be set by an external divider connected to the VOSC pin.
Figure 29.
Switching frequency selection and VOSC pin
The suggested voltage range for VOSC pin is 0.3 V to 2 V, for better switching frequency
programmability.
D
V
OUT
V
IN
--------------
=
OSC
OUT
OSC
SNS
OSC
IN
OUT
ON
SW
K
1
V
K
V
T
D
f
α
=
α
OSC
V
OSC
V
IN
---------------
=
α
OUT
V
SNS
V
OUT
--------------
=
OSC
2
1
2
OSC
SW
K
1
R
K
f
+
=
α
=
PM6670
VOSC
R1
R2
VIN
PM6670S
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PM6670S 3 A SWITCHING CONTROLLER, QCC24
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