KIT33701DWBEVB Freescale Semiconductor, KIT33701DWBEVB Datasheet - Page 31

• Manufacturer Part Number: KIT33701DWBEVB
• Description: KIT FOR 33701 POWER SUPPLY
• Manufacturer: Freescale Semiconductor
• Type: LDO Controllers & Regulatorsr

Specifications of KIT33701DWBEVB

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Input: 2.8 ~ 6V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MC34701
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Output: -
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: 34701

.
capacitor C
capacitor, and ESR is the equivalent series resistance of the
output capacitor.
calculated as follows:
should yield at least 45 deg. phase margin Φ
loop as depicted in the
Selecting Buck Regulator Output Voltage
selecting the right value of the resistors R1, R2 and R4, and
can be determined from the following formula (see
page
Analog Integrated Circuit Device Data
Freescale Semiconductor
Pha se
[Deg.]
G ain
[dB]
-2 70
-3 60
The frequency of the zero created by the ESR of the output
Where C
The frequency of the compensating network pole can be
The well designed and compensated buck regulator
The 34701 buck regulator output voltage can be set by
-180
-20
20
-40
0
30
1.0
for the component references):
Figure 30. Buck Control Loop Bode Plot
O
O
is calculated as:
is the value of the buck regulator output
f LC
10
f
p c ( )
f
f z(c)
z ESR
(
Figure
Φ
=
f BW
m
)
----------------------------------------
2πC2
=
f z(E SR) f p (FF)
------------------------- -
2πC
100
30, page 31.
-------------------------
(
R1
1
R1R3
O
1
ESR
+
Frequency [k Hz ]
R3
)
10 00
m
of its overall
f p(c)
Figure
10000
29,
affected by the voltage drop caused by the inductor serial
resistance and the regulator output current. In those
applications which do not require precise output voltage,
setting the formula for calculating selected output voltage can
be simplified as follows:
Linear Regulator Output Voltage
by a simple resistor divider according to the following formula:
the resistor divider R
Where V
It is apparent that the buck regulator output voltage is
The output voltage of the linear regulator (LDO) can be set
Where V
Figure 31
R2
Figure 31. 34701Linear Regulator Circuit
(V
V
I
R
(V
V
R
R
O
=
O
LDO
L
U
L
Ref
Ref
Ref
R2
Ref
is the output load current,
is the DC resistance of the inductor L.
is the “lower” resistor of the LDO resistor divider.
is the “upper” resistor of the LDO resistor divider,
V
is the selected output voltage,
describes the 34701 linear regulator circuit with
Ref
2.8 V to 6.0 V Input
= 0.8V typ.) at the INV pin,
= 0.8V typ.) at the LFB pin,
=
is the buck regulator reference voltage
is the linear regulator reference voltage
is the LDO selected output voltage,
MC34701
V
V
×
Ref
LDO
---------------------------------------------------------------------------------------- -
(
------------------------------------------------------- -
U
V
LDRV
LCMP
LDO
, R
VIN1
LFB
O
×
CS
+
=
-------------------------------------------------------------- -
(
L
V
I
V
O
setting the output voltage V
O
Ref
×
R4
–
R
V
×
L
R S
Ref
LDO
Compensation
) V
⎛
⎝
R U
R L
–
1
)
1
1
TYPICAL APPLICATIONS
+
×
Ref
R
------ -
R
(
-------------------------
R1
R1 R4
U
L
⎞
⎠
+
V LDO
C LDO
+
×
V
-------------------------
R4
O
–
R1
)
V
Ref
LDO
34701
31
.