TYPICAL APPLICATIONS
COMPONENTS CALCULATION
Variable Definition
D= Boost Duty Cycle
Vout= Output Voltage
VD= Diode Forward Voltage
Vin= Input Voltage
2
-------------------------------------------------------
CComp1
=
fCross × RComp × π × 2
GM
VSW= VDROP of Internal Switch
ΔVout= Output Voltage Ripple Ratio
Iinavg= Average Input Current
---------------------------
=
CComp2
6.28 × FSW
Slope Compensation
Iout= Output Current
Slope Compensation can be expressed either in terms of
Ampers/Second or as Volts/Second, through the use of the
transfer resistance.
r=Input Current Ratio
Iinmax= Maximum input current
IrmsCin= RMS current for Input Capacitor
IrmsCout= RMS current for Output Capacitor
L= Inductor
The following formula express the Slope Compensation in
terms of V/μs:
rw= Inductor winding DC Resistance
FSW= Boost Switching Frequency
CSG= Current Sense Gain = 0.2 V/A
ACSA= Current Sense Amplifier Gain = 9
RSense= Current Sense Resistor = 22mohm
Cout= Output Capacitor
(Vout – Vin) × CSG
---------------------------------------------------
=
VSLOPE
L × 2
Where “L” is in μH
In order to have this slope compensation, the following
resistor should be set.
RComp= Compensation Resistor
GM= OTA Transconductance
33×103
-------------------
=
RSLOPE
VSLOPE
ESRCout= ESR of Output Capacitor
fRHPZ= Right Half Plane Zero Frequency
fCross= Crossover Frequency
CComp1= Compensation Capacitor
CComp2= Shunt Compensation Capacitor
VSLOPE= Slope Compensation (V/μs)
RSLOPE= External Resistor for Slope Compensation
34844
Analog Integrated Circuit Device Data
Freescale Semiconductor
31
FREESCALE [ Freescale ]
