max5073atit Maxim Integrated Products, Inc., max5073atit Datasheet - Page 21

• Manufacturer Part Number: max5073atit
• Description: Max5073 2.2mhz, Dual-output Buck Or Boost Converter With Internal Power Mosfets
• Manufacturer: Maxim Integrated Products, Inc.

The boost converter compensation gets complicated
due to the presence of a right-half-plane zero f
The right-half-plane zero causes a drop in-phase while
adding positive (+1) slope to the gain curve. It is impor-
tant to drop the gain significantly below unity before the
RHP frequency. Use the following procedure to calcu-
late the compensation components.
1) Calculate the LC double-pole frequency, F
Figure 8. Buck-Boost Application
OUTPUT2
12V/0.2A
the right half plane zero frequency.
2.2MHz, Dual-Output Buck or Boost Converter
f
f
LC
ZERO RHP
=
______________________________________________________________________________________
,
2
Boost Converter Compensation
π
×
VL
=
1
L
OFF
(
OUT OUT
1
−
−
2
ON
D
CLOCK
π
D
OUT
C
×
)
2
L
R
OUT
(
MIN
1
2
3
4
5
6
7
)
CLKOUT
BST2/VDD2
DRAIN2
DRAIN2
EN2
FB2
COMP2
SYSTEM
CLOCK
28
8
with Internal Power MOSFETs
ZERO,RHP
27
9
LC
EP
OUTPUT2
, and
26
10
MAX5073
11
.
25
INPUT
12
24
where:
Target the unity-gain crossover frequency for:
2) Place a zero
where R
13
23
BST1/VDD1
14
22
PGOOD1
DRAIN1
DRAIN1
COMP1
F
PGOOD1
EN1
FB1
≥ 10kΩ.
*CONNECT PGND AND SGND TOGETHER AT ONE POINT NEAR
THE RETURN TERMINALS OF THE V+ AND VL BYPASS CAPACITORS.
PGOOD2
21
20
19
18
17
16
15
C
F
D
(
R
=
f
f
Z
C
(
= −
MIN
1
2
1
≤
π
=
)
×
f
2
ZERO RHP
=
π
V
0 75
ON
V
OUT
.
I
×
IN
OUT MAX
OFF
5
R
,
V
1
1
F
×
OUT
(
×
f
LC
OUTPUT1
C
VL
F
)
×
INPUT
)
R
F
at 0.75 x f
OUTPUT1
3.3V/2A
LC
.
21