MCZ34702EWR2 Freescale Semiconductor, MCZ34702EWR2 Datasheet - Page 30

• Manufacturer Part Number: MCZ34702EWR2
• Description: IC PWR SUPPLY 3A SW 32-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MCZ34702EWR2

• Applications: Controller, Power QUICC™ I, II
• Voltage - Input: 2.8 ~ 6 V
• Number Of Outputs: 2
• Voltage - Output: 7.75V, 0.8 ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-SOIC (7.5mm Width)
• Output Current: 3 A
• Input Voltage: 2.8 V to 6 V
• Switching Frequency: 300 KHz
• Mounting Style: SMD/SMT
• Duty Cycle (max): 95 %
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

BUCK REGULATOR CONTROL CIRCUIT
topology with feed-forward to achieve an excellent line and
external resistor R4 provides the feed-forward ramp
waveform, the amplitude of which is proportional to the input
voltage, thus providing the feed-forward function.
control loop gain and phase versus frequency.
buck regulator output L-C filter, and its frequency can be
calculated as:
is the inductance value of the output filter inductor L.
as follows.
30
34702
TYPICAL APPLICATIONS
The 34702 buck regulator utilizes a PWM Voltage Mode
The integrated 40pF capacitor C
Figure 30
The first double pole on the Bode plot is created by the
Where C
The frequency of the compensating zero can be calculated
O
shows the Bode plot of the 34702 buck regulator
is the value of the buck output capacitor and L
f
LC
=
----------------------
2π C
1
O
F
L
charged through the
Figure 29. Buck Regulator Control Circuit
TYPICAL APPLICATIONS
load regulation. The control circuit block diagram is shown in
Figure
integrated capacitor C
transfer function, the frequency of which can be calculated
from the following formula.
The feed-forward implemented by resistor R4 and
Where V
29.
f
p FF
(V
V
V
generator (V
(
IN
m1
Ref
Ref
)
is the buck regulator input voltage,
is the ramp generated by the internal ramp
=
L
= 0.8V typ.) at the INV pin,
is the buck regulator reference voltage
--------------------------------------------------------------- -
-------
f
sw
1
f
z c ( )
×
m1
F
(
------------------------------- -
Analog Integrated Circuit Device Data
V
=
creates a pole in the overall loop
IN
= 0.5V typ.).
R4C
--------------------------------------- -
2πC2 R1
V
–
IN
V
F
Ref
(
1
)
Freescale Semiconductor
+
+
V
R3
m1
)
×
-------------------- -
2πR4C
1
F