TPS54073  

Manufacturer Part Number  TPS54073 
Description  As a member of the SWIFT™ family of dc/dc regulators, the TPS54073 lowinput voltage highoutput current synchronous buck PWM converter integrates all required active components 
Manufacturer  Texas Instruments 
TPS54073 datasheet 

Specifications of TPS54073  

Iout(max)(a)  14  Vin(min)(v)  2.2 
Vin(max)(v)  4  Vout(min)(v)  0.9 
Vout(max)(v)  2.5  Iq(typ)(ma)  13 
Switching Frequency(max)(khz)  700  Switch Current Limit(typ)(a)  14.5 
Topology  Buck  Operating Temperature Range(c)  40 to 85 
Pin/package  28HTSSOP  Duty Cycle(max)(%)  90 
Regulated Outputs(#)  1 
PrevNext
TPS54073
SLVS547 – FEBRUARY 2005
............................................................................................................................................................................................
V
V
x
OUT
I
I
=
+
L(PK)
OUT(MAX)
x
1.6
V
IN(MAX)
For this design, the RMS inductor current is 14.001 A,
and the peak inductor current is 14.43 A. The Vishay
IHLP5050CZ01 style output inductor with a value of
2.2 H meets these current requirements. Increasing
the inductor value decreases the ripple current and
the corresponding output ripple voltage. The inductor
value can be decreased if more margin in the RMS
current is required. In general, inductor values for use
with the TPS54073 falls in the range of 1 H to 3.3
H, depending on the maximum required output
current.
Capacitor Requirements
The important design factors for the output capacitor
are dc voltage rating, ripple current rating, and
equivalent series resistance (ESR). The dc voltage
and ripple current ratings cannot be exceeded. The
ESR is important because along with the inductor
current it determines the amount of output ripple
voltage. The actual value of the output capacitor is
not critical, but some practical limits do exist.
Consider the relationship between the desired
closedloop crossover frequency of the design and
LC corner frequency of the output filter. In general, it
is desirable to keep the closedloop crossover
frequency at less than 1/5 of the switching frequency.
With high switching frequencies such as the 700 kHz
frequency of this design, internal circuit limitations of
the TPS54073 limit the practical maximum crossover
frequency to about 70 kHz. To allow for adequate
phase gain in the compensation network, the LC
corner frequency should be about one decade or so
below the closedloop crossover frequency. This
limits the minimum capacitor value for the output filter
to:
1
K
C
+
OUT(MIN)
2p
L
OUT
CO
Where K is the frequency multiplier for the spread
between f
and f
. K should be between 5 and 15,
LC
CO
typically 10 for one decade difference. For a desired
crossover of 40kHz and a 2.2 H inductor, the
minimum value for the output capacitor is 304
using a minimum K factor of 6.5. Increasing the K
factor would require using a larger capacitance. The
selected output capacitor must be rated for a voltage
greater than the desired output voltage plus one half
the ripple voltage. Any derating amount must also be
included. The maximum RMS ripple current in the
output capacitors is given by
Equation
12
Submit Documentation Feedback
V
x
IN (MAX)
OUT
x
x
x
I
L
F sw
0.8
OUT
COUT(RMS)
(7)
The calculated RMS ripple current is 201 mA in the
output capacitors.
The maximum ESR of the output capacitor is
determined by the amount of allowable output ripple
as specified in the initial design parameters. The
output ripple voltage is the inductor ripple current
times the ESR of the output filter; therefore, the
maximum specified ESR as listed in the capacitor
data is given by
+ N
ESR
MAX
and the maximum ESR required is 29 mΩ. A
capacitor that meets these requirements is a Cornell
Sanyo POSCAP 6TPD33M rated at 6.3 V with a
maximum ESR of 0.015 Ω and a ripple current rating
of 2 A. An additional small 0.1 F ceramic bypass
capacitor C13 is a also used.
Other capacitor types work well with the TPS54073,
depending on the needs of the application.
Compensation Components
The external compensation used with the TPS54073
allows for a wide range of output filter configurations.
A large range of capacitor values and types of
dielectric are supported. The design example uses
Type3 compensation consisting of R1, R3, R5, C6,
C7, and C8. Additionally, R2 along with R1 forms a
voltage divider network that sets the output voltage.
These component reference designators are the
same as those used in the SWIFT Designer
2
Software. There are a number of different ways to
design a compensation network. This procedure
outlines a relatively simple procedure that produces
(8)
good results with most output filter combinations. Use
the SWIFT Designer Software for designs with
unusually high closedloop crossover frequencies,
low value, low ESR output capacitors such as
ceramics or if you are unsure about the design
F
procedure.
When designing compensation networks for the
TPS54073, a number of factors need to be
considered. The gain of the compensated error
amplifier should not be limited by the openloop
amplifier gain characteristics and should not produce
excessive gain at the switching frequency. Also, the
9:
closedloop crossover frequency should be set less
than onefifth of the switching frequency, and the
Product Folder Link(s):
TPS54073
www.ti.com
* V
V
V
OUT
PVIN(MAX)
+ 1
V
L
12
PVIN(MAX)
OUT
Equation 10
:
V
L
F sw
0.8
IN(MAX)
OUT
DV
C
* V
V
V
OUT
IN(MAX)
OUT
Copyright © 2005, Texas Instruments Incorporated
OUT
F sw
(9)
P*P(MAX)
(10)
Related parts for TPS54073  

Part Number  Description  Manufacturer  Datasheet 
TPS5401  The TPS5401 device is a 42V, 0  Texas Instruments 

TPS54010  As a member of the SWIFT™ family of dc/dc regulators, the TPS54010 lowinput voltage, highoutput current synchronous buck PWM converter integrates all required active components  Texas Instruments 

TPS54040Q1  The TPS54040 device is a 42V 0  Texas Instruments 

TPS54062  The TPS54062 device is a 60 V, 50mA, synchronous stepdown converter with integrated high side and low side MOSFETs  Texas Instruments 

TPS54040  Texas Instruments 


TPS54040A  Texas Instruments  
TPS54060  Texas Instruments 


TPS54060Q1  Texas Instruments 


TPS54060A  Texas Instruments  
TPS54040DGQR  IC DCDC CONV STPDN SYNC 10MSOP  Texas Instruments 

TPS54060DGQR  IC CONV STPDWN BUCK .5A 10MSOP  Texas Instruments 

TPS54060DRCT  IC DCDC CONV STPDN BUCK 10SON  Texas Instruments 

TPS54040DGQ  IC STEPDOWN SWIFT CONV 10MSOP  Texas Instruments 

TPS54060DGQ  IC STEPDOWN SWIFT CONV 10MSOP  Texas Instruments 

TPS54010PWP  IC SYNC BUCK PWM SWTCHR 28HTSSOP  Texas Instruments 
