Texas Instruments TPS40100 User manual

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.

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.

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)

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

4 SCHEMATIC

Figure 1: TPS40100EVM-001 Power Stage / Control Schematic

Figure 2: TPS40100EVM-001 Margin Control

Component values are for reference only.

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.

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.

LOAD1

3.3V @

10A

Voltmeter

FAN

+3.3Vout

--++

VIN

10.8V -

13.2V -

TP3

TP4

TP14

TP13

TEXA S INSTRUMENTS

TPS40100EVM-001

12Vto3.3V@10A

HPA089A

Voltmeter

Ammeter

GND GND

TrackingEnable

JumperDisable

Pos itio n

J4 Margin Enable

Po w e r GoodandSyncIn

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

TP18TP17

Metal Ground Barrel

Probe Tip

Tip and Barrel Vout ripple and

transient measurement for TP17 and

TP18

TP17

TP18

J8 J7

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

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.

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

TrackingEnable

Jumper

Disabled

12 9 6

11 85

13 10 7 4

Enable S1

4123

Tracking EngageS2

LOAD1

3.3V @

10A

--++

TP14

TP13

Voltmeter

Remote+SenseJumper

Enabled

Remote GNDSenseJumper

Enabled

Max 6" length

Input Supply

Voltmeter

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.

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.

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