MC34716EP Freescale Semiconductor, MC34716EP Datasheet - Page 22

• Manufacturer Part Number: MC34716EP
• Description: IC CONVERTER DDR 26QFN
• Manufacturer: Freescale Semiconductor

Specifications of MC34716EP

• Applications: Converter, DDR
• Voltage - Input: 3 ~ 6 V
• Number Of Outputs: 2
• Voltage - Output: 0.7 ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 26-QFN
• Output Voltage: 0.7 V to 3.6 V
• Output Current: 5 A
• Input Voltage: 3 V to 6 V
• Switching Frequency: 1 MHz
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

22
34716
TYPICAL APPLICATIONS
F
1. Choose a value for R1 (R2only applies to Channel 1)
2. Consider a Crossover frequency of one tenth of the
3. Knowing the LC frequency, the Frequency of Zero 1
4. Calculate R
This gives the result
R
Z
COMP
1
F
VOUT
switching frequency, set the Zero pole frequency to
Fcross/10
and Zero 2 in the compensation network is equal to
F
frequency
=
LC
=
INV
SW
F
Figure 12. Type III compensation network
2
2
P
π
x
x
x
x
1
π
F
F
=
*
F
*
LC
P
1
R
ESR
2
0
C
1
π
F
=
S
=
F
C
C
*
R
C
=
by placing the first pole at the ESR zero
C
F
2
Xx
10
F
Sx
Sx
1
1
R
π
Z
L
F
2
1
x
S
π
F
=
C
CROSS
*
L
S
R
C
1
2
Co
X
Fx
Fx
π
C
*
1
OX
X
R1
=
1
R
*
1
x
2
F
ESR
=
R
π
C
PO
S
F
F
R2
S
*
Z
Z
=
x
1
1
2
=
R
=
2
=
=
1
C
π
2
F
C
F
π
2
Ox
F
P
*
π
Z
1
*
2
1
F
*
1
R
P
1
R
1
1
C
1
F
C
S
Z
S
2
TRACKING CONFIGURATIONS
2 by connecting VDDQ to the VREFIN terminal. It has an
internal resistor divider that allows an output of VDDQ/2.
LAYOUT GUIDELINES
consideration. First, there are high di/dt signals present, and
the traces carrying these signals need to be kept as short and
as wide as possible to minimize the trace inductance, and
therefore reduce the voltage spikes they can create. To do
this, an understanding of the major current carrying loops is
important. See
components, should be placed in such a way as to minimize
the loop size to prevent coupling to other parts of the circuit.
Also, the current carrying power traces and their associated
return traces should run adjacent to one another, to minimize
the amount of noise coupling. If sensitive traces must cross
the current carrying traces, they should be made
perpendicular to one another to reduce field interaction.
sensitive nodes need consideration. The critical small signal
components are the ones associated with the feedback
circuit. The high impedance input of the error amp is
especially sensitive to noise, and the feedback and
compensation components should be placed as far from the
switch node, and as close to the input of the error amplifier as
possible. Other critical small signal components include the
bypass capacitors for VIN, VREFIN, and VDDI. Locate the
bypass capacitors as close to the pin as possible.
recommended. Dedicate one layer, usually the layer under
the top layer, as a ground plane. Make all critical component
ground connections with vias to this layer. Make sure that the
power grounds, PGND1 and PGND2 are connected directly
to the ground plane and not routed through the thermal pad
or analog ground. Dedicate another layer as a power plane
and split this plane into local areas for common voltage nets.
dedicated trace to the input supply This will help prevent
noise on the buck regulator's power inputs (PVIN1 and
PVIN2) from injecting switching noise into the IC’s analog
circuitry.
5. Equating pole 2 to 5 times the Crossover Frequency to
The 34716 allows default Ratiometric tracking on channel
The layout of any switching regulator requires careful
Second, small signal components which connect to
The use of a multi-layer printed circuit board is
The IC input supply (VIN) should be connected with a
5
achieve a faster response and a proper phase margin
•
F
CROSS
C
Figure
=
X
F P2
=
13. These loops, and their associated
2
Analog Integrated Circuit Device Data
π
=
*
--------------------------------------- -
2π R
R
F
•
C
C
F
F
F
Freescale Semiconductor
1
------------------- -
C
F
C
F
P
F
+
2
C
C
−
X
x
1