Datasheet

www.ti.com
TPS40040 , TPS40041
SLUS700D – MARCH 2006 – REVISED DECEMBER 2007
Definition of Symbols
SYMBOL DESCRIPTION
V
IN(max)
Maximum operating input voltage
V
IN(min)
Minimum operating input voltage
V
INRIPPLE
Peak-to-peak ac ripple voltage on V
IN
V
OUT
Target output voltage
V
OUTRIPPLE
Peak-to-peak ac ripple voltage on V
OUT
I
OUT(max)
Maximum operating load current
I
RIPPLE
Peak-to-peak ripple current through the output filter inductor
I
L_PEAK
Peak ripple current through the output filter inductor
I
L_RMS
Root mean squared current through the output filter inductor
I
RMS_CIN
Root mean squared current in input capacitor
F
SW
Switching frequency
F
CO
Desired control loop cross-over frequency
A
MOD
Low frequency gain of the pulse width modulator
V
CONTROL
PWM control voltage (error amplifier output voltage - V
COMP
)
F
RES
L-C filter resonant frequency
F
ESR
Output capacitors ’ ESR zero frequency
F
P1
First pole frequency in error amplifier compensation
F
P2
Second pole frequency in error amplifier compensation
F
Z1
First zero frequency in error amplifier compensation
F
Z2
Second pole frequency in error amplifier compensation
Q
G1_Q1
Total gate charge of upper switch MOSFET
Q
G2_Q2
Total gate charge of synchronous rectifier MOSFET
R
DS(on_Q1)
“ ON ” drain-to-source resistance of upper switch MOSFET
R
DS(on_Q2)
“ ON ” drain-to-source resistance of synchronous rectifier MOSEFT
P
CON_Q1
Conduction losses in upper switch MOSFET
P
SW_Q1
Switching losses in upper switch MOSFET
P
CON_Q2
Conduction losses in synchronous rectifier MOSFET
Q
GD_Q1
Gate-to-drain charge of upper switch MOSFET
Post threshold gate-to-source charge of the upper switch MOSFET. (Estimate from Q
G
vs. V
GS
if not provided in
Q
GS2_Q1
MOSFET data sheet)
V
FB
Internal reference voltage as measured on FB pin.
V
RAMP_slope
Slope of internal PWM ramp
A
PS(Fco)
V
COMP
to V
OUT
gain at desired loop cross-over frequency. (dB)
A
MID-BAND
V
OUT
to V
COMP
gain at desired loop cross-over frequency (V/V)
Copyright © 2006 – 2007, Texas Instruments Incorporated 29
Product Folder Link(s): TPS40040 TPS40041