MC34704 FREESCALE [Freescale Semiconductor, Inc], MC34704 Datasheet - Page 38

• Manufacturer Part Number: MC34704
• Description: Multiple Channel DC-DC Power Management IC
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

38
34704
FUNCTIONAL DEVICE OPERATION
COMPONENT CALCULATION
F
1. Output LC filter cutoff frequency (F
F
2. Cutoff frequency due to capacitor ESR:
3. Crossover frequency (or bandwidth):
The passive components associated to these frequencies are calculated with the following formulas.
On the 34704 V
C1
C2
R2
R3
C3
ESR
LC
=
=
=
=
=
=
=
------------------
V
⎛
⎝
⎛
⎝
⎛
⎝
⎛
⎝
------------------------- -
2
Vin
------------------------------------- -
2
--------------------------- -
2
--------------------------- -
2
--------------------------- -
2
--------------------------- -
2
RAMP
LC
min
C
1
F
F
F
F
1
1
1
Z2
1
Z1
P1
P2
OUT
OUT
⎛
⎜
⎝
1
R1
C1
C2
R2
----------------
D
RAMP
min
ESR
1
⎞
⎠
⎞
⎠
⎞
⎠
⎞
⎠
2
⎞
⎟
⎠
is half of 1.2V since each operation mode spends only half the ramp.
⎛
⎝
---------------------------- -
2
F
1
PO
R1
⎞
⎠
LC
):
[Hz]
[Hz]
charge of canceling some of these poles and zeros to
achieve stability in the system. The following poles and
zeroes frequencies are provided by the type 3 compensation.
F
F
F
The Type 3 external compensation network will be in
BW
P1
PO
=
=
=
F
F
F
----------
ESR
BW
10
SW
F
F
Z1
2P
Analog Integrated Circuit Device Data
=
=
0.9F
F
----------
SW
2
LC
Freescale Semiconductor
F
22
=
[Hz]
1.1F
LC