MC34713EP Freescale, MC34713EP Datasheet - Page 17

• Manufacturer Part Number: MC34713EP
• Manufacturer: Freescale

Specifications of MC34713EP

• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Pin Count: 24
• Mounting: Surface Mount
• Package Type: QFN
• Case Length: 4mm
• Screening Level: Industrial
• Lead Free Status / RoHS Status: Compliant

and may present a hidden danger to the ultimate supply
stability. Poor quality capacitors have widely disparate ESR
value, which can make the closed loop response
inconsistent.
TYPE III COMPENSATION NETWORK
regulation output voltages. To accomplish this requires a high
DC gain. But with high gain comes the possibility of instability.
The purpose of adding compensation to the internal error
amplifier is to counteract some of the gains and phases
contained in the control-to-output transfer function that could
jeopardized the stability of the power supply. The Type III
compensation network used for 34713 comprises two poles
(one integrator and one high frequency pole to cancel the
zero generated from the ESR of the output capacitor) and two
zeros to cancel the two poles generated from the LC filter as
shown in
Analog Integrated Circuit Device Data
Freescale Semiconductor
In order to find the maximum allowed ESR,
The effects of the ESR is often neglected by the designers
Power supplies are desired to offer accurate and tight
Io_step
Figure
Io
Figure 8. Transient Parameters
9.
dt_I_rise
Worst case
assumption
Current
response
Consider the crossover frequency, F
gain at one-tenth of the switching frequency, F
frequency, it can be obtained the values of R
frequency:
Then,
where R
This gives as a result,
Calculate Rs by placing the Pole 1 at the ESR zero
Generator
V
Ramp
DDI
Regulator
Bandgap
V
Figure 9. Type III Compensation Network
REFIN
F
SW
O
Comparitor
is a user selected resistor. Knowing the LC
PWM
F
Amplifier
Reference
CROSS
Selection
C F
Error
Gate
Driver
=
34713
=
-------------------------------------- -
2π R O F
----------------------------
2π R O C F
•
COMP
BOOT
VOUT
•
SW
INV
10
10
CROSS
TYPICAL APPLICATIONS
CROSS
V
C
O
C
C
X
R
&
=
BOOT
S
⇒
S
, of the open loop
L
V
F
R
C
F
REF
F
SW.
and C
R
R
⎛
⎝
O
B
R
------ -
R
O
B
S
:
+
34713
1
C
⎞
⎠
O
17