Texas Instruments SLVP089 User manual

SLVP089 Synchronous Buck
Converter Evaluation Module
1998 Mixed-Signal Linear Products
User’s Guide

Printed in U.S.A.
07/98 SLVU001A

SLVP089 Synchronous Buck
Converter Evaluation Module
User’s Guide
Printed on Recycled Paper
Literature Number: SLVU001A
July 1998

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Copyright 1998, Texas Instruments Incorporated

Related Documentation From Texas Instruments
iii
Read This First
Preface
Read This First
About This Manual
This user’s guide is a reference manual for the SLVP089 Synchronous Buck
ConverterEvaluationModuleusedtoevaluatetheperformanceoftheTL5001
PWMController. Thisdocumentprovides information to assistmanagersand
hardware engineers in application development.
How to Use This Manual
This manual provides the information and instructions necessary to design,
construct, operate, and understand the SLVP089. Chapter 1 describes and
lists the hardware requirements; Chapter 2 describes design considerations
andprocedures;andAppendixAcontainsthedatasheetfortheTL5001PWM
Controller
Related Documentation From Texas Instruments
The following books describe the TL5001 and related support tools. To obtain
acopyof anyoftheseTIdocuments,calltheTexasInstrumentsLiteratureRe-
sponseCenterat(800)477–8924.Whenordering,pleaseidentifythe bookby
its title and literature number.
TL5001 Pulse-Width-Modulation Control Circuits Data Sheet (Literature
number SLVS084C). It contains electrical specifications, available tem-
perature options, general overview of the device, and application in-
formation.
Designing with the TL5001C PWM Controller Application Report
(Literature number SLVA034).

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iv
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Running Title—Attribute Reference
v
Chapter Title—Attribute Reference
Contents
1 Hardware 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Introduction 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Schematic 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Input/Output Connections 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Board Layout 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Bill of Materials 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 Test Results 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Design Procedure 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 Introduction 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Operating Specifications 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Design Procedures 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Duty Cycle Estimate 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Output Filter 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.3 Power Switch 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.4 Synchronous Switch and Rectifier 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.5 Snubber Network 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.6 Controller Functions 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.7 Loop Compensation 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Running Title—Attribute Reference
vi
Figures
1–1 Typical Synchronous Buck Converter 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–2 Schematic Diagram 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–3 Input/Output Connections 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–4 Board Layout 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–5 Efficiency Vs Load 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–6 Power Switch Turn-On and Delay from Q2 Off 1-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–7 Power Switch Turn-Off and Delay to Q2 On 1-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–8 Inductor and Output Ripple 1-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1 Power Stage Bode Plot 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–2 Compensation Network 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–3 Bode Plot 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–4 Output Response 2-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tables
1–1 Bill of Materials 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–2 Line/Load Regulation, 3.3-V (Total Variation) 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–3 Load Regulation and Ripple, 3.3-V (9-V Input) 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1 Operating Specifications 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
Chapter Title—Attribute Reference
Hardware
The SLVP089 Synchronous Buck Converter Evaluation Module (SLVP089)
providesa method for evaluating theperformanceoftheTL5001pulse-width-
modulation(PWM)controller.Thedevicecontainsallofthecircuitrynecessary
to control a switch-mode power supply in a voltage-mode configuration. This
manual explains how to construct basic power conversion circuits including
the design of the control chip functions and the basic loop. This chapter in-
cludes the following topics:
Topic Page
1.1 Introduction 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Schematic 1–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Input/Output Connections 1–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Board Layout 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Bill of Materials 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 Test Results 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1

Introduction
1-2
1.1 Introduction
Synchronous buck converters provide the smaller size and higher efficiency
required by electronic equipment, particularly portable battery-operated
equipment. The synchronous buck converter reduces power losses
associated with a standard buck converter by substituting a power MOSFET
for the commutating diode. This reduces the typical 0.5-V to 1-V diode drop
to 0.3 V or less and increases system efficiency by up to 10 percent.
Continuous-current mode is desirable and is used in this EVM for the low
peak-to-average current ratio. Figure 1–1 shows a typical synchronous buck
converter.
Figure 1–1.Typical Synchronous Buck Converter
Controller
FB
R1
R2
Q1
Q2
R3
R4
CR1
+
C2
+
C1
VO
VI
L1
Transistor Q1 is the power switch and Q2 is the synchronous switch. A diode
inparallelwithQ2 allowsinductorcurrentflowduringthe deadtimewhenboth
transistors are turned off. If dead time is not present in this configuration, high
transient shoot-through currents will flow during the transition when one tran-
sistor is turning on and the other is turning off, usually resulting in destruction
of the power stage switches.
TheSLVP089evaluationmodulewillsupplyanominal3.3-Voutputoveraload
rangefrom0to3Ausingadcinputvoltageof5.5 Vto12V.Fullload efficiency
is typically 90 percent.

Schematic
1-3
Hardware
1.2 Schematic
Figure 1–2.Schematic Diagram
DTC
COMP
R9
RT
OUT
SCP
GND
VCC
6
3
4
7
R9
1
5
FB
+C1
µ1F
R2
C3
0.0022 µF
C2
0.033 µF
R8
C9 0.22 µF
C15
µ1.0 F R6
2
8
U1
TL5001 1IN
2OUT
GND
VCC
2
45
7
2IN
3
1OUT
VDD
REG 8
61
R10
R13
IRF7201
NMOS
Q2
U2
TPS2812
C14
0.1 µF
CR3
BAS16ZX
C11
0.47µF
C5
100 µF
C10
100 µF
+
2
3
4
1
J1
I
V
GND
2
3
4
1J2
5.5 V to 12 V
Q1
IRF7406
PMOS
C4
µ0.022 F R3
R4
CR1
30BQ015
R7
C6
1000 pF
L1
27
µH
C12
100µF+C7
100
+C13
10µFµF3.3 V
RTN
+
GND
I
V
3.3 V
RTN
CR2
BAS16ZX
15 Ω
121 kΩR12 10 kΩ
R11 30 kΩ
90.9 kΩ
1.00 kΩ
1.6 kΩ
R5
10 kΩ
10 kΩ
2.32 kΩ
180 Ω
3.3 Ω
1 kΩ
Note: Frequency is set to 100 kHz by R9. See TL5001 data sheet for the curve of oscillator frequency versus timing resistance.

Input/Output Connections
1-4
1.3 Input/Output Connections
Figure 1–3 shows the input/output connections to the SLVP089.
Figure 1–3.Input/Output Connections
C5 Q1
Q2
TL5001
+3.3V, 3 AMP
SYNC. RECT BUCK
U2
R5 R7
R13C6
C11
C10 L1
J1 J2
R12 CR3
CR2
R11
C14 R6
R10 JMP1
C12 C8 C13
TEXAS INSTRUMENTS C15
R4 R3
C4 C3
R1
R9
R8
C9
C1
SLVP089
EVAL BOARD
REV2
R2 C2
U1
–+
LOAD –
+
Power Supply
CR1
11
Notes: 1) Source power should be able to supply a minimum of 2.5 A at 5.5-V input and/or 1.1-A at 12-V input.
2) Loadshouldbeabletosinkupto3Awithadequatepowerrating.Resistiveloadswithadequateratingsmaybeused.

Board Layout
1-5
Hardware
1.4 Board Layout
Figure 1–4 shows the SLVP089 board layout.
Figure 1–4.Board Layout
C5 Q1
Q2
TL5001
+3.3V, 3 AMP
SYNC. RECT BUCK
U2
R5 R7
R13 C6
C11
C10 L1
J1 J2
R12 CR3
CR2R11
C14 R6
R10 JMP1
C12 C8 C13
TEXAS INSTRUMENTS C15
R4 R3
C4 C3
R1
R9
R8
C9
C1
SLVP089
EVAL BOARD
REV2
R2 C2
U1
CR1
11

Bill of Materials
1-6
1.5 Bill of Materials
Table 1–1 lists materials required for the SLVP089.
Table 1–1.Bill of Materials
Qty Reference Part Number Mfr Description
1 C1 ECS-T1CY105R Panasonic Capacitor, Tant, 1 m F, 20%, A Case
1 C11 Standard Capacitor, Cer, 0.47 m F, 10%, X7R, 1210
1 C13 C3225Y5V1C106Z TDK Capacitor, Cer, 10 m F, 10 V, Y5V,3225
1 C14 Standard Capacitor, Cer, 0.1 m F, 10%, X7R, 1206
1 C2 Standard Capacitor, Cer, 0.033 m F, 10%, X7R, 1206
1 C3 Standard Capacitor, Cer, 0.0022 m F, 10%, X7R, 0805
1 C4 Standard Capacitor, Cer, 0.022 m F, 10%, X7R, 0805
4 C5, C7,
C10, C12 TPSD107M010R0100 AVX Capacitor, Tant, 100
m F, 10 V, D Case
1 C6 Standard Capacitor, Cer, 1000 pF, 5%, NPO, 0805
1 C9 Standard Capacitor, Cer, 0.22 m F, 10%, X7R, 1210
1 CR1 30BQ015 IR Rectifier, Schottky, 3 A, 15 V
2 CR2, CR3 BAS16ZXCT Zetex Diode, Signal, SOT-23
2 J1, J2 Standard Connector, 4-pin header, 25 Mil, 0.1′′ Sp. Gold
1 L1 NOVA 1 Nova Mag Inductor, 27 m H , 20%, 3 A
1 Q1 IRF7406 IR Transistor, P-CH FET, 30 V, 0.04 W , 4.7 A, SO-8
1 Q2 IRF7201 IR Transistor, N-CH FET, 30 V, 0.03 W , 7 A, SO-8
1 R1 Standard Resistor, 1.00 k W, 1%, 0805
2 R12, R13 Standard Resistor, 10 k W, 5%, 0805
1 R2 Standard Resistor, 1.6 k W, 5%, 0805
1 R3 Standard Resistor, 180 W, 5%, 0805
1 R4 Standard Resistor, 2.32 k W, 1%, 0805
1 R5 Standard Resistor, 10 k W, 1%, 0805
1 R6 Standard Resistor, 15 W, 5%, 0805
1 R7 Standard Resistor, 3.3 W, 5%, 0805
1 R8 Standard Resistor, 121 k W, 1%, 0805
1 U1 TL5001CD TI IC, PWM, SO-8
1 U2 TPS2812D TI IC, dual MOSFET driver, SO-8
1SLVP089 PWB

Test Results
1-7
Hardware
1.6 Test Results
Tables1–2and1–3,alongwithFigures1–5through1–8,showthetestresults
for the SLVP089.
Table 1–2.Line/Load Regulation, 3.3-V (Total Variation)
Line/Load 0.3 A 0.9 A 1.5 A 3.0 A 5.0 A Load Reg.
5.5 V Vo(V) 3.330 3.329 3.328 3.324 3.320 0.18%
6.0 V Vo(V) 3.330 3.329 3.328 3.324 3.320 0.18%
7.0 V Vo(V) 3.330 3.328 3.328 3.325 3.321 0.15%
8.0 V Vo(V) 3.330 3.329 3.328 3.325 3.321 0.15%
9.0 V Vo(V) 3.331 3.330 3.328 3.325 3.321 0.18%
10 V Vo(V) 3.331 3.330 3.328 3.325 3.321 0.18%
11 V Vo(V) 3.331 3.330 3.328 3.325 3.321 0.18%
12 V Vo(V) 3.331 3.330 3.329 3.325 3.321 0.18%
Line Reg. 0.03% 0.06% 0.03% 0.03% 0.03%
Note: The calculation for load regulation only accounts for the worst case of load variation under the normal voltage condition
(i.e., 3.3 V at 3 A). All voltages were measured at the PCB header pins.
Table 1–3.Load Regulation and Ripple, 3.3-V (9-V Input)
Load No Load 0.50 A 1.0 A 2.0 A 3.0 A 5.0 A Reg.
Vo(V) 3.331 3.330 3.329 3.327 3.325 3.321 0.18%
Vo Ripple (mV P–P) 16 16 18 24 24 32
Vo Spikes (mV P–P) 0 24 24 34 48 60
Figure 1–5.Efficiency Vs Load
85
80
75
70 0123
Efficiency –%
90
95
Load Current –A
EFFICIENCY
vs
LOAD CURRENT
100
45
VI= 9 V
VI= 5.5 V
VI= 12 V

Test Results
1-8
Figure 1–6.Power Switch Turn-On and Delay from Q2 Off
VCC = 12 V
IO= 1.5 A
Q1 DRAIN
5 V/DIV
Q2 GATE
5 V/DIV
20 ns/Div
1
2
Figure 1–7.Power Switch Turn-Off and Delay to Q2 On
VCC = 12 V
IO= 1.5 A
Q1 Drain
5 V/Div
Q2 Gate
5 V/Div
1
2
20 ns/Div

Test Results
1-9
Hardware
Figure 1–8.Inductor and Output Ripple
VCC = 12 V
IO= 1.5 A Inductor
Ripple
1 A/Div
Output
Ripple
20 mV/Div
2 µs/Div
1–DC
2–AC

1-10

2-1
Chapter Title—Attribute Reference
Design Procedure
There are many possible ways to proceed when designing power supplies.
This chapter shows the procedure used in the design of the SLVP089. The
chapter includes the following topics:
Topic Page
2.1 Introduction 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Operating Specifications 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Design Procedures 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2

Introduction
2-2
2.1 Introduction
The SLVP089 is a dc-dc synchronous buck converter module that provides a
3.3-Voutputatupto3Awithaninputvoltagerangeof5.5Vto12V.ThePWM
controller is a TL5001 operating at a nominal frequency of 100 kHz. The
TL5001 is configured for a maximum duty cycle of 100 percent and has short-
circuit protection built in. The synchronous power stage consists of a PMOS
switch and an NMOS synchronous rectifier.