Texas Instruments TPS40090EVM-002 Installation and operating instructions

User’s Guide
1
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User’s Guide

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EVM IMPORTANT NOTICE
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Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2003, Texas Instruments Incorporated

3
DYNAMIC WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the input voltage range of 0 Vdc to100 Vdc.
Exceeding the specified input range may cause unexpected operation and/or irreversible damage to the EVM.
If there are questions concerning the input range, please contact a TI field representative prior to connecting
the input power.
Applying loads outside of the specified output range may result in unintended operation and/or possible
permanent damage to the EVM. Please consult the EVM User’s Guide prior to connecting any load to the EVM
output. If there is uncertainty as to the load specification, please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than 50°C. The EVM
is designed to operate properly with certain components above 50°C as long as the input and output ranges are
maintained. These components include but are not limited to linear regulators, switching transistors, pass
transistors, and current sense resistors. These types of devices can be identified using the EVM schematic
located in the EVM User’s Guide. When placing measurement probes near these devices during operation,
please be aware that these devices may be very warm to the touch.
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright 2004, Texas Instruments Incorporated

SLUU195 − June 2004
4TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
TPS40090 Multi-Phase Buck Converter and TPS2834
Drivers Steps-Down from 12-V to 1.5-V at 100 A
Systems Powe
r
Contents
1 Introduction 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Features 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Schematic 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Component Selection 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Test Setup 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Test Results/Performance Data 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 Layout Considerations 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 EVM Assembly Drawing and PCB Layout 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 List of Materials 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 Introduction
The TPS40090EVM−002 multi-phase dc-to-dc converter utilizes the TPS40090 multi-phase
controller and TPS2834 adaptive driver to step down a 12-V input to 1.5-V at 420 kHz. The
output current can exceed 100 A. The TPS40090 provides fixed-frequency, peak current-mode
control with forced-phase current balancing. Phase currents are sensed by the voltage drop
across the DC resistance (DCR) of inductors. Other features include a single voltage operation,
true differential output voltage sense, user programmable current limit, capacitor-programmable
soft-start and a power good indicator. Device operation is specified in the TPS40090
datasheet[1].
TPS40090EVM-002 can be configured into 2-, 3− or 4-phase operation. For 2-phase operation,
populate R65 and R66 to tie PWM2 and PWM4 up to internal 5-V and leave components in
related phases unpopulated. For 3-phase operation, tie PWM4 to BP5 through R66 only. For
4-phase operation, leave both R65 and R66 unpopulated.
In this user’s guide, all the tests are conducted under 4 phase operation.

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5
TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
2 Features
Table 1. TPS40090EVM−002 Performance Summary
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Input voltage range 10.5 12.0 14.0
V
Output voltage set point 1.477 1.508 1.540 V
Output current range VIN = 12 V 0 100 120 A
Line regulation(1) IOUT rising from 10 A to 100 A,
10.5 V ≤VIN ≤14 V ±0.1%
Load regulation IOUT rising from 10 A to 100 A ±0.3%
Load transient response voltage
IOUT rising from 10 A to 100 A −160
mVPK
Load transient response voltage
change IOUT falling from 100 A to 10 A 200 mVPK
Load transient response recovery
IOUT rising from 10 A to 100 A < 10
s
Load transient response recovery
time IOUT falling from 100 A to 10 A < 15 µs
Loop bandwidth IOUT = 100 A, IOUT = 10 A 89 kHz
Phase margin IOUT = 100 A 40 °
Input ripple voltage 80 200
mVPK
Output ripple voltage 15 25 mVPK
Output rise time ms
Operating frequency 370 418 454 kHz
Full load efficiency VIN = 12 V, VOUT = 1.5 V,
IOUT = 100 A 84.3%
Current sharing tolerance VIN = 12 V, VOUT = 1.5 V,
IOUT = 100 A ±5% ±10%
3 Schematic
+
12V +
Phase Programming
R65 R66
4−phase open open
3−phase open 1k
2−phase 1k 1k
Figure 1. TPS40090EVM−002 Schematic Part 1 − TPS40090 Controller and Pre-Bias Circuit

SLUU195 − June 2004
6TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
TRANS_EN
Figure 2. TPS40090EVM−002 Schematic Part 2 − Driver Circuit and Load Transient Generator

SLUU195 − June 2004
7
TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
+ +
+
1.5V/100A
+ +
+ + +
Figure 3. TPS40090EVM−002 Schematic Part 3 − Power Stage
4 Component Selection
4.1 Frequency of Operation
The clock oscillator frequency for the TPS40090 is programmed with a single resistor from RT
(pin 16) to signal ground. Equation (1) from the datasheet allows selection of the RTresistor in
kΩfor a given switching frequency in kHz.
RT+R12 +KPH ǒ39.2 103 f*1.024
PH *7Ǔ(kW)
where
•KPH is the coefficient that depends on the number of active phases
•fPH is the single phase frequency, in kHz
•for 2-phase and 3-phase configurations KPH=1.333
•for 4-phase KPH=1.0 is a single phase frequency, kHz.
The RTresistor value is returned by the last expression in kΩ. For 420 kHz, RTis calculated as
65.8 kΩ and a resistor with a 64.9-kΩ standard value is used.
(1)

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8TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
4.2 Inductance Value
The output inductor value for each phase can be calculated from the volt-second during off time,
shown in equation (2).
L+VOUT
f IRIPPLE ǒ1*VOUT
VIN(max)Ǔ
where
•IRIPPLE is usually chosen to be between 10% and 40% of maximum phase current IPH(max).
With IRIPPLE = 20% of IPH(max), there is a ripple current of 5 A, and the inductance value is found
to be 0.63 µH. Using SPM12550−R62M300 inductors from TDK, each had inductance of 0.6µH
and resistance of 1.75-mΩ.
In multi-phase high current buck converter design, due to the ripple cancellation factor from
interleaving, the inductor value could be smaller than that in a single phase operation. But from
conduction loss point of view, the inductor value tends to be big to reduce the ripple current, thus
losses.
4.3 Input Capacitor Selection
The bulk input capacitor selection is based on the input voltage ripple requirements. Due to the
interleaving of multi phase, the input RMS current is reduced. The input ripple current RMS
value over load current is calculated in equation (3).
DIIN(nom) ǒNPH,D
Ǔ+
ȧ
ȱ
ȲǒD*kǒNPH,D
Ǔ
NPH Ǔ ǒkǒNPH,D
Ǔ)1
NPH *DǓȧ
ȳ
ȴ)ǒNPH
12 D2Ǔ ƪVOUT (1*D)
L f ǒIOUTǓƫ2
ȧ
ȱ
ȲǒkǒNPH,D
Ǔ)1Ǔ2 ǒD*kǒNPH,D
Ǔ
NPH Ǔ3
)kǒNPH,D
Ǔ2 ǒkǒNPH,D
Ǔ)1
NPH *DǓ3
ȧ
ȳ
ȴ
where
•kǒNPH,D
Ǔ+floor ǒNPH DǓ
•floor(x) is the function to return the greatest integer less than NPH ×D
•NPH is the number of active phases
Figure 4 shows the input ripple current RMS value over the load current versus duty cycle with
different number of active phases.
(2)
(3)

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9
TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
0
0.1
0.2
0.5
0.6
0.4
0.3
0 10 20304050 60708090100
Duty Cycle − %
IRMS_CIN(nom)−Normalized RMS Input − A
NPH = 1
NPH = 2
NPH = 3
NPH = 4
NPH = 6
Figure 4. Input Ripple Current RMS Value Overload Current
The maximum input ripple RMS current can be estimated as shown in (4).
I^IOUT DIIN(nom) ǒ4, DminǓ+3.18 A
It is also important to consider a minimum capacitance value which limits the voltage ripple to a
specified value if all the current is supplied by the onboard capacitor. For a typical ripple voltage
of 150 mV the maximum ESR is calculated in (5) as:
ESR +DV
DI+150 mV
3.18 A +47 mW
Two 68-µF, 20-V Oscon capacitors (20SVP68M) from Sanyo are placed on the input side of the
board. The ESR is 40 mΩfor each capacitor.
4.4 Output Ripple Cancellation and Capacitor Selection
Due to the interleaving of channels, the total output ripple current is smaller than the ripple
current from a single phase. The ripple cancellation factor is expressed in equation (6).
DIOUT ǒNPH,DǓ+ǒNPH
P
i+1Ťi*NPH DŤǓ
ƪNPH*1
P
i+1ǒŤi*NPH DŤ)1Ǔƫ
kǒNPH,DǓ+if ǒNPH v1, DIOUT(D), DIOUT ǒNPH,D
ǓǓ
(4)
(5)
(6)

SLUU195 − June 2004
10 TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A
where
•D is the duty cycle for a single phase
•NPH is the number of active phases
•K (NPH) is the intermediate function for calculation
In this case, NPH=4 and Dmin=0.107 which yields k=0.573.
The actual output ripple is calculated in equation (7)
IRIPPLE +VOUT
L f KǒNPH,D
Ǔ+1.5 V
0.6mH 420 kHz 0.573 +3.41 A
0
0.2
0.6
0.4
0.8
1.0
0 10 20304050 60708090100
Duty Cycle − %
IRMS_Cout(nom) − Normalized RMS Input − A
NPH = 1
NPH = 2
NPH = 3
NPH = 6
NPH = 4
Figure 5. Output Ripple Current Cancellation
Selection of the output capacitor is based on many application variables, including function, cost,
size, and availability. There are three ways to calculate the output capacitance.
1. The minimum allowable output capacitance is determined by the amount of inductor ripple
current and the allowable output ripple, as given in equation (8).
COUT(min) +IRIPPLE
8 f VRIPPLE +3.41 A
8 420 kHz 10 mV +101 mF
In this design, COUT(min) is 101-µF with VRIPPLE=10 mV. However, this affects only the
capacitive component of the ripple voltage, and the final value of capacitance is generally
influenced by ESR and transient considerations.
2. ESR limitation. (To limit the ripple voltage to 10 mV, the capacitor ESR should be less than
the value calculated in equation (9)).
RCt+ VRIPPLE
IRIPPLE +10 mV
3.41 A +2.93 mW
(7)
(8)
(9)