# TPS54040-Q1

Manufacturer Part NumberTPS54040-Q1
DescriptionThe TPS54040 device is a 42-V 0
ManufacturerTexas Instruments
TPS54040-Q1 datasheet

## Specifications of TPS54040-Q1

Iout(max)(a)0.5Vin(min)(v)3.5
Vin(max)(v)42Vout(min)(v)0.8
Vout(max)(v)39Iq(typ)(ma)0.116
Switching Frequency(max)(khz)2500Switch Current Limit(typ)(a)0.6
TopologyBuck,Inverting Buck-BoostOperating Temperature Range(c)-40 to 125
Regulated Outputs(#)1
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TPS54040-Q1
SLVSA26C – JANUARY 2010 – REVISED AUGUST 2011
DETAILED DESCRIPTION (continued)
Selecting the Switching Frequency
The switching frequency that is selected should be the lower value of the two equations,
Equation
13.
Equation 12
is the maximum switching frequency limitation set by the minimum controllable on time.
Setting the switching frequency above this value will cause the regulator to skip switching pulses.
Equation 13
is the maximum switching frequency limit set by the frequency shift protection. To have adequate
output short circuit protection at high input voltages, the switching frequency should be set to be less than the
fsw(maxshift) frequency. In
Equation
account that the output voltage decreases from the nominal voltage to 0 volts, the fdiv integer increases from 1 to
8 corresponding to the frequency shift.
In
Figure
41, the solid line illustrates a typical safe operating area regarding frequency shift and assumes the
output voltage is zero volts, and the resistance of the inductor is 0.130Ω, FET on resistance of 0.2Ω and the
diode voltage drop is 0.5V. The dashed line is the maximum switching frequency to avoid pulse skipping. Enter
these equations in a spreadsheet or other software or use the SwitcherPro design software to determine the
switching frequency.
(
æ
I
æ
ö
´
1
L
f
=
´ ç
ç
÷ ç
(
)
SW max skip
(
t
V
è
ø è
ON
IN
æ
(I
Rdc
V
f
div
´
+
L
OUTSC
f
=
´ ç
( )
SW hift
ç
(
t
V
I x Rhs
-
ON
è
IN
L
I
inductor current
L
Rdc
inductor resistance
V
maximum input voltage
IN
V
output voltage
OUT
V
output voltage during short
OUTSC
Vd
diode voltage drop
R
switch on resistance
DS(on)
t
controllable on time
ON
ƒ
frequency divide equals (1, 2, 4, or 8)
DIV
2500
2000
1500
1000
500
0
Figure 41. Maximum Switching Frequency vs. Input Voltage
22
13, to calculate the maximum switching frequency one must take into
)
Rdc V
Vd
ö
+
+
OUT
÷
)
÷
-
I
´
Rhs Vd
+
L
ø
ö
Vd)
+
÷
)
÷
Vd
+
ø
Skip
Shift
20
30
10
V - Input Voltage - V
I
www.ti.com
Equation 12
V = 5.0 V
O
40