Texas Instruments TPS40100 User manual

1
User Guide
SLUU224 – JUNE 2005
Using the TPS40100
A 12V Input, 3.3V Output, 10A Synchronous Buck Controller
System Power Management – DC/DC Controllers
1 INTRODUCTION
The TPS40100EVM-001 evaluation module (EVM) is a synchronous buck converter providing a fixed 3.3V output
at up to 10A from a 12V input bus. The EVM is designed to start up from a single input supply, with no additional
bias voltage required. The module uses a TPS40100 midrange input synchronous buck controller.
2 DESCRIPTION
TPS40100EVM-001 is designed to use a regulated 12V +/-10% (10.8V-13.2V) bus to produce a regulated 3.3V
output at up to 10A of load current. The EVM is designed to demonstrate the TPS40100 in a typical regulated
bus to low-voltage application while providing a number of test points to evaluate the performance of the
TPS40100. The EVM includes features to demonstrate voltage tracking, margin up/down, enable/disable and
power good. A synchronization pin is provided to allow the EVM to be synchronized to an external clock.
2.1 APPLICATIONS
•Non-Isolated Medium Current Point of Load and low voltage bus converters.
•Merchant Power Modules
•Networking Equipment
•Telecommunications Equipment
•DC Power Distributed Systems
2.2 FEATURES
•10.8V – 13.2V input range
•3.3V fixed output
•10 Adc Steady State Output Current
•Output margin up and down support
•Tracking voltage input to support simultaneous sequencing
•Power good indicator
•Frequency synchronization input
•Remote sensing scheme
•380kHz switching frequency
•Single Main Switch MOSFET and Single Synchronous Rectifier MOSFET
•Single Component Side, surface mount design on a 3.0” x 3.25” evaluation board
•Four Layer PCB with all components on top side
•Convenient test points for probing critical waveforms
•Test points for full loop analysis as well as control to output
2.2.1 USING REMOTE SENSE (J3)
TPS40100EVM-001 provides the user with remote sense capabilities. Remote sense is used to provide more
accurate load regulation by compensating for losses over terminal connections and load wire resistance.
When remote sense is used properly, the converter will regulate the voltage at the point where sense connections
are placed. These remote sense connections are usually placed at the intended load. As the load is increased
the direct output of the converter will rise to compensate for IR losses.

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Caution: long wiring connections can cause the converter to act irregularly. This can show up as pulse width
jitter or an oscillatory effect on the ripple voltage. If this condition occurs, check the set up and make adjustments.
Please see section 5.3.2 in this users guide.
2.2.2 SIMULTANEOUS TRACKING (J3)
The EVM is equipped to provide the ability to demonstrate the tracking feature of the TPS40100. In addition, the
module can be configured to have multiple TPS40100-EVMs track. The voltage tracking function allows the
TPS40100 to track an external ramp (provided on EVM). This tracking feature allows single or multiple modules to
track an external ramp in order to comply with the demands of many microprocessor and memory applications.
Please see section 5.3.3 of the test setup section of the users guide.
2.2.3 ENABLE (SW2)
The EVM is equipped with an enable/disable switch. Please see section 5.3.4 in test set up section of the users
guide. Closing S1 will disable the device by pulling the UVLO pin of the TPS40100 low. Opening the S1 will
enable the device, provided that the appropriate input voltage is present. J3 pin 4 is an enable monitor pin
providing a connection for user observation.
2.2.4 MARGIN UP/DOWN (J4)
The margin up and down feature of the EVM provides the user with the ability to trim or margin the output of the
converter up/down by 3% or 5%. EVM is equipped with convenient jumper settings to give the user the ability to
trim the output voltage. Please see section 5.3.5 in the test set up section of this users guide for more detailed
test setup information.
2.2.5 POWER GOOD (J1)
The EVM contains a power good pin to provide the user with a “power ok” signal. This pin is pulled up through a
resistor to the 5VBP pin of the TPS40100. If any of the following conditions occur the power good pin will pull low;
•Soft-start is active (Vss < 3.5V)
•Tracking is active (Vtrackout>.7V)
•Vfb < 0.61V
•Vfb > 0.77V
•Vuvlo < 1.33V
•Overcurrent condition exists
•Die temperature is greater than 165°C
This pin can be monitored with an oscilloscope to observe its behavior. Please see section 5.3.6 in the test setup
section of the users guide.
2.2.6 SYNCHRONIZTION (J1)
To TPS40100-EVM can be synchronized to an external clock source of a higher frequency than that of the free
running PWM clock. This is a feature that can aid with input filter design. It is recommended that the
synchronization frequency be no more than 120% of the free running frequency. The EVM is configured to a
switching frequency of 370 kHz, so the external frequency into the synchronization pin should be no more than
470 kHz. Please see section 5.3.6 of the test setup section of this users guide.

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3 ELECTRICAL PERFORMANCE SPECIFICATION
Parameter Notes and Conditions Min Typ Max Units
INPUT CHARACTERISTICS
Input Voltage Range 10.8 13.2 V
Max Input Current VIN = 10.8V, IOUT = 10A 3.5 A
No-Load Input Current VIN = 13.2V, IOUT = 0A 100 mA
OUTPUT CHARACTERISTICS
Output Voltage 3.22 3.30 3.39 V
Output Voltage
Regulation
Line Regulation (10.8V<VIN<13.2V, IOUT = 5A)
Load Regulation (0A<IOUT<10A, VIN = 12V)
1
1
%
%
Output Voltage Ripple VIN = 13.2V, IOUT = 10A 25 mVpp
Output Load Current 0 10 A
Output Over Current 15 A
SYSTEM CHARACTERISTICS
Switching Frequency 350 380 410 kHz
Full Load Efficiency VOUT = 3.3V, IOUT = 10A V12V_IN = 10.8V
V12V_IN = 12V
V12V_IN = 13.2V
93.9
93.5
93.4
%
Table 1: TPS40100EVM-001 Electrical & Performance Specifications

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4 SCHEMATIC
Figure 1: TPS40100EVM-001 Power Stage / Control Schematic

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Figure 2: TPS40100EVM-001 Margin Control
Component values are for reference only.

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5 TEST SET UP
5.1 EQUIPMENT
5.1.1 VOLTAGE SOURCE
VIN
The input voltage source (VIN) should be a 0-15V variable DC source capable of 5Adc. Connect VIN to J2 as
shown in Figure 3.
5.1.2 METERS
Ammeter1: 0-5Adc, ammeter
Voltmeter1: VIN, 0-15V voltmeter
Voltmeter2: VIN, 0-5V voltmeter
5.1.3 LOADS
LOAD1
The Output Load (LOAD1) should be an Electronic Constant Current Mode Load capable of 0-10Adc @ 3.3V
5.1.4 Recommended Wire Gauge
VIN to J2.
The connection between the source voltage, VIN and J2 of EVM can carry as much as 5 Adc. The minimum
recommended wire size is AWG #16. Shorter lengths of input wire will aid in reducing inductance and provide
better overall performance.
J5 to LOAD1 (Power Pins 2, 3)
The power connection between J5 of EVM and LOAD1 can carry as much as 10 Adc. It is recommended that the
user use AWG#16 wire. It is recommended that the load wires be kept as short as possible. This will aid in
performance, most notably in transient response.
J2 to LOAD1 (Remote Sense)
If remote sense is to be used, ensure that J6 and J7 are in the remote sense enable position (shunt pins 1&2).
Load wires and sense wires should be kept less than 6 inches to ensure proper functionality. The remote sense
wires connecting J5 (pins 1 and 4) and LOAD1 carry less than 1Adc. The minimum recommended wire size is
AWG #22, with the total length of less than 6 inches long.
5.1.5 OTHER
FAN
This evaluation module includes components that can get hot to the touch. A small fan capable of 200-400 LFM is
required to reduce component surface temperatures to prevent user injury. The EVM should not be left
unattended while powered or probed while the fan is not running.
OSCILLOSCOPE
A 60MHz or faster oscilloscope can be used to monitor many points on the EVM. For output ripple voltage
measurements the Oscilloscope should be set for 20 MHz bandwidth limiting, 1MΩimpedance, AC coupling,
1µs/division horizontal resolution, 10-20mV/division vertical resolution for taking output ripple measurements.
FUNCTION GENERATOR
A function generator capable of source a 0-5V square wave at frequencies past 400Khz.

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5.2 EQUIPMENT SETUP
5.2.1 Initial EVM Jumper and Switch Settings
Figure 4 is the basic test set up recommended for evaluating the TPS40100EVM-001. EVM is shipped with the
following in the default position:
1. Enable switch (S1) open across pins 2&3. This is the enable position.
2. Tracking enable jumper (J8) has shunt positioned across pins 1&2 disabling the tracking feature.
3. Tracking engage switch (S2) open across pins 2&3. This enables the tracking ramp to charge.
4. Remote sense jumpers (J6 and J7) have shunts positioned across pins 2&3 enabling local
connector sensing.
5. Margin shunts positioned in the margin disable position.
5.2.2 Procedure
1. Working at an ESD workstation, make sure that any wrist straps, bootstraps or mats are
connected referencing the user to earth ground before power is applied to the EVM. Electrostatic
smock and safety glasses should also be worn.
2. Prior to connecting the DC input source, VIN, it is advisable to limit the source current to 5.0A
maximum. Make sure VIN is initially set to 0V and connected as shown in Figure 4.
3. Connect an ammeter between the positive output of the input supply and the positive input of the
EVM. (J2, Pin 1)
4. Connect voltmeter Voltmeter #1 to TP3 and TP4 as shown in Figure 2.1. These are the EVM
input supply monitoring points.
5. Connect LOAD1 to J5 as shown in Figure 2.1. Set LOAD1 to constant current mode to sink 0Adc
before input voltage is applied.
6. Connect voltmeter #2 across TP13 and TP14 as shown in Figure 2.1. This is the EVM output
supply monitoring point. Note: this configuration is local sensing.
7. Remove oscilloscope probe jacket and position probe as shown below in Figure 3. TP17 and
TP18 are implemented to provide the user with the means to achieve good noise immune
measurements of ripple voltage and transient response.
Figure 3: Probe position for ripple measurement
8. Place Fan as shown in Figure 4 and turn on, making sure air is flowing across the EVM.

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LOAD1
3.3V @
10A
-
+
Voltmeter
#1
FAN
+3.3Vout
+
-
--++
VIN
10.8V -
13.2V -
+
TP3
TP4
TP14
TP13
TEXA S INSTRUMENTS
TPS40100EVM-001
12Vto3.3V@10A
HPA089A
J5
J2
Voltmeter
#2
-
+
-
+
Ammeter
#1
GND GND
GND GND
TrackingEnable
JumperDisable
Pos itio n
J4 Margin Enable
J1
Po w e r GoodandSyncIn
J5
Tracking Inand Enable
Monitor
EnableS1
TrackingEngageS2
EnableSW1
Sw itc h Clos ed= OFF
Sw itchOpen=ON
-
1MΩ, DC
1V/div
20mHzBW
Remote +SenseJumper
Disabled
Remote GNDSenseJumper
Disabled
1
2
3
4
TP18TP17
Metal Ground Barrel
Probe Tip
Tip and Barrel Vout ripple and
transient measurement for TP17 and
TP18
TP17
TP18
J8 J7
J6
1
2
3
1
2
3
Figure 4: TPS40100EVM-001 Recommended Test Set-Up
5.2.3 START UP / SHUT DOWN PROCEDURE
1. Increase VIN (V1) from 0V to 12Vdc.
2. Observe that Vout has risen to its nominal voltage.
3. Vary LOAD1 from 0 – 10Adc
4. Vary VIN from 10.8dc to 13.2Vdc
5. Decrease LOAD1 to 0A.
6. Decrease VIN to 0V.
5.2.4 EQUIPMENT SHUTDOWN
1. Shut Down Oscilloscope
2. Shut down LOAD
3. Shut down VIN
4. Shut down FAN

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5.3 OTHER TESTS
5.3.1 ADJUSTING OUTPUT VOLTAGE (R1 & R3)
The regulated output voltage can be adjusted by changing the values of the feedback resistors, R1 and R3. R19
and R17 are located in the feedback to provide the user with positive remote sense and the ability to perform loop
analysis with a frequency/gain analyzer. Resistors R12 and the parallel combination of R1 and R3 are the
dominant resistors associated with setting the output voltage. Listed below are the equations associated for
establishing the output voltage.
Rparallel R1 R3⋅()
R1 R3+()
:= Vout Vref R12 R17+()
Rparallel 1+
⎡
⎢
⎣
⎤
⎥
⎦
⋅:= Rparallel Vref
Vout Vref−
⎛
⎜
⎝
⎞
⎠
R17 R12+()⋅:=
Where VVREF = 0.690V, R17 = 49.9Ω, R12 = 18.2k Ω. R1//R3 can be adjusted to provide user defined output
voltages. Table 2 contains values for R1//R3 to generate popular output voltages.
VOUT R1//R3
(Rparallel)
R1 R3
3.3V 4.82K 12.4 K 7.87 K
2.5V 6.95K 7.15 K 237 K
2.2V 8.33K 8.66 K 205 K
2.0V 9.61K 10.0 K 237 K
1.8V 11.34K 12.1 K 178 K
1.5V 15.55K 16.2 K 365 K
1.2V 24.69K 26.1 K 422 K
Table 2: Adjusting Vout with R1//R3
5.3.2 Remote Sense Test Set-Up
In order for the remote sense feature of the TPS40100EVM-001 to function properly, it is
essential that the test setup be configured correctly. Use the following steps to set up the remote
sense:
1) Ensure that the remote sense jumpers J7&J8 are shunted across pins 1&2
2) Connect load wires of a max length of 6 inches from pin 2 of J5 (+Vout) to the positive
terminal of the load. Connect same length of wire from pin 3 of J5 (RTN) to the negative
terminal of the load. Be sure to properly gauge the load wires for 10A. AWG#16 is
recommended.
3) Connect sense wire from J5 pin 1 to the positive terminal of the load. This is the +sense
line. Be sure to not exceed 6 inches in length. AWG#22 wire is recommended.
4) Connect sense wire from J5 pin 4 to the negative terminal of the load. This is the –sense
line. 6 inches maximum length. AWG#22 wire is recommended.
5) Monitor voltage at TP13 and TP14 using a voltmeter. This will be the regulated voltage at
the load.
6) Monitor voltage at J5 pins 2, 3. This is the voltage at the output connector. This voltage
will increase based on load.
7) Set load to 0A, constant current. Both monitoring points should read very close to the
same value.

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8) Increase load gradually and observe the difference in voltages present at the monitoring
points. The set voltage (3.3V) will be regulated at the load; this will be noted at TP13 and
TP14. The direct output of the converter (J5 pin 2, 3) will read a higher voltage. As IR
losses increase over load wires and terminals the direct output of the converter will
compensate by raising the voltage to keep within regulation at the load.
Caution: long distance runs from the output of the converter and the load will cause erratic behavior. This can
show up as pulse width jitter or an oscillatory effect on the ripple voltage. If this condition occurs, check the set up
and make adjustments. Please see Figure 5 below for test up.
TP1
TP2
J2
-
+
TrackingEnable
Jumper
Disabled
1
12 9 6
11 85
13 10 7 4
3
2
1
Enable S1
J3
15
14
4123
Tracking EngageS2
LOAD1
3.3V @
10A
-
+
--++
TP14
TP13
J5
Voltmeter
#2
-
+
Remote+SenseJumper
Enabled
Remote GNDSenseJumper
Enabled
Max 6" length
Max 6" length
Max 6" length
Input Supply
Voltmeter
#3
+
-
Voltagemonitoredattheoutput
connector.
NOTE: This w ill r ead a higher
valueasloadcurrentincreases.
Voltagew illberegulatedtoset
voltageattheLOAD.
Voltagemonitoredattheload.
Readingcanbetakenatthe
load if desired. NOTE: This is
thepointtowhichtheconverter
w illberegulating to.
4
2
3
1
Figure 5: TPS40100EVM-001 Recommended Remote Test Set-Up
5.3.3 Voltage Tracking Test Set-Up
The following procedure is for a single EVM demonstration of the track function. Please see Figure 6 below.
1. Shunt pins 2&3 of J8 (Tracking Enable Jumper)
2. Tracking Engage Switch (S2) should be in the closed position.
3. Connect oscilloscope probe to the TRACKING IN pin (J3 pin 1) and the Vout (TP 17&18).
4. Connect load to the output of the EVM and set from 1A – 10A. (User selectable)
5. Power on the EVM with an input voltage of 10.8V – 13.2V. ( Allow for SS voltage to reach 3.5V to
ensure proper tracking performance or wait 1-2 seconds)
6. Open the Tracking Engage Switch (S2) (Shorting pins 1&2 open) and observe how Vout tracks
the TRACKING IN pins rising voltage. Waveforms should be simultaneous.
7. Close the Tracking Engage (S2) (Shorting pins 2&3 open) and observe how Vout tracks the
TRACKING IN pin’s falling voltage. Waveforms should be simultaneous.