Texas Instruments Incorporated AN-1986 User's Guide

VIN (V)

EFFICIENCY (%)

10 15 20 25 30

100

95

90

85

80

1 Introduction

This evaluation board showcases the LM3429 NFET controller used with a boost current regulator. It is designed to drive 9 to 12 LEDs at a maximum average LED current of 1A from a DC input voltage of 10 to 26V.

The evaluation board showcases most features of the LM3429 including PWM dimming, overvoltage protection and input under-voltage lockout. It also has a right angle connector (J7) which can mate with an external LED load board allowing for the LEDs to be mounted close to the driver. Alternatively, the LED+ and LED- banana jacks can be used to connect the LED load.

The boost circuit can be easily redesigned for different specifications by changing only a few components (see Alternate Designs ). Note that design modifications can change the system efficiency for better or worse. See the LM3429 LM3429Q1 N-Channel Controller for Constant Current LED Drivers (SNVS616) data sheet for a comprehensive explanation of the device and application information.

User's Guide

SNVA404B–July 2009–Revised May 2013

AN-1986 LM3429 Boost Evaluation Board

All trademarks are the property of their respective owners.

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

Figure 1. Efficiency with 9 Series LEDS AT 1A

1

D1

OVP

LM3429

nDIM

PGND

NC

DAP

GATE

COMP

CSH

RCT

IS

HSN

HSP

L1

C9

R6

Q1

R1

C7

R13

R5

1

2

3

4

5

6

7

14

13

12

11

10

9

8

R7

R8

AGND

R10

Q3

R4

PWM

R18

R11

R9

R20

C12

V

IN

V

CC

V

IN

GND

V

IN

C8

R2

R3

C1

C2, C3, C16, C18

C4, C6, C17, C19

R12

TP7

TP10

TP1

TP11

TP12

J1

J2

U1

LED-

1 2 3

5 6 7

14 13 12

10

9 8

J7

4 11

J5

TP3

TP2

LED+

J4

Schematic

2 Schematic

www.ti.com

2

Figure 2. Board Schematic

AN-1986 LM3429 Boost Evaluation Board SNVA404B–July 2009–Revised May 2013

Submit Documentation Feedback

www.ti.com

3 Pin Descriptions

Pin Name Description Application Information

1 V 2 COMP Compensation Connect a capacitor to AGND.

3 CSH Current Sense High dimming, connect a controlled current source or a potentiometer

4 RCT Resistor Capacitor Timing

5 AGND Analog Ground

6 OVP Over-Voltage Protection voltage lockout (OVLO). Turn-off threshold is 1.24V and

7 nDIM Not DIM input

8 NC No Connection Leave open. 9 PGND Power Ground

10 GATE Gate Drive Output Connect to the gate of the external NFET. 11 V

12 IS Main Switch Current Sense R

13 HSP

14 HSN

DAP Star ground, connecting AGND and PGND.

(15)

IN

CC

DAP Thermal pad on bottom of IC

Pin Descriptions

Input Voltage

Internal Regulator Output Bypass with a 2.2 µF–3.3 µF, ceramic capacitor to PGND.

High-Side LED Current Sense Connect through a series resistor to the positive side of the LED

Positive current sense resistor.

High-Side LED Current Sense Connect through a series resistor to the negative side of the

Negative LED current sense resistor.

Bypass with 100 nF capacitor to AGND as close to the device as possible in the circuit board layout.

Connect a resistor to AGND to set the signal current. For analog to AGND as detailed in the Analog Dimming section.

Connect a resistor from the switch node and a capacitor to AGND to set the switching frequency.

Connect to PGND through the DAP copper circuit board pad to provide proper ground return for CSH, COMP, and RCT.

Connect to a resistor divider from VOto program output overhysteresis for turn-on is provided by 20 µA current source.

Connect a PWM signal for dimming as detailed in the PWM Dimming section and/or a resistor divider from VINto program input under-voltage lockout (UVLO). Turn-on threshold is 1.24V and hysteresis for turn-off is provided by 20 µA current source.

Connect to AGND through the DAP copper circuit board pad to provide proper ground return for GATE.

Connect to the drain of the main N-channel MosFET switch for

sensing or to a sense resistor installed in the source of

DS-ON

the same device.

4 Bill of Materials

Qty Part ID Part Value Manufacturer Part Number

2 C1, C4 0.1 µF X7R 10% 100V TDK C2012X7R2A104K 4 C2, C3, C16, C18 4.7 µF X7R 10% 100V MURATA GRM55ER72A475KA01L 3 C6, C17, C19 2.2 µF X7R 10% 100V TDK C4532X7R2A225K 1 C7 1000 pF COG/NPO 5% 50V MURATA GRM2165C1H102JA01D 1 C8 1 µF X7R 10% 16V MURATA GRM21BR71C105KA01L 1 C9 2.2 µF X7R 10% 16V MURATA GRM21BR71C225KA12L 1 C12 0.1 µF X7R 10% 25V MURATA GRM21BR71E104KA01L 1 D1 Schottky 100V 12A VISHAY 12CWQ10FNPBF 4 J1, J2, J4, J5 banana jack KEYSTONE 575-8 1 J7 2 x 7 shrouded header SAMTEC TSSH-107-01-SDRA 1 L1 33 µH 20% 6.3A COILCRAFT MSS1278-333MLB 1 Q1 NMOS 100V 40A VISHAY SUD40N10-25 1 Q3 NMOS 60V 260 mA ON-SEMI 2N7002ET1G 1 R1 12.4 kΩ 1% VISHAY CRCW080512k4FKEA 1 R2 0Ω 1% VISHAY CRCW08050000Z0EA 2 R3, R20 10Ω 1% VISHAY CRCW080510R0FKEA

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

3

Bill of Materials

1 R4 16.9 kΩ 1% VISHAY CRCW080516k9FKEA 1 R5 1.43 kΩ 1% VISHAY CRCW08051k43FKEA 1 R6 0.04Ω 1% 1W VISHAY WSL2512R0400FEA 2 R7, R8 1.0 kΩ 1% VISHAY CRCW08051k00FKEA 1 R9 0.1Ω 1% 1W VISHAY WSL2512R1000FEA 1 R10 35.7 kΩ 1% VISHAY CRCW080535k7FKEA 1 R11 15.8 kΩ 1% VISHAY CRCW080515k8FKEA 2 R12, R13 10.0 kΩ 1% VISHAY CRCW080510k0FKEA 1 R18 750 kΩ 1% VISHAY CRCW0805750kFKEA 7 TP1, TP2, TP3, TP7, turret KEYSTONE 1502-2

1 U1 Buck-boost controller TI LM3429

www.ti.com

TP10, TP11, TP12

4

AN-1986 LM3429 Boost Evaluation Board SNVA404B–July 2009–Revised May 2013

Submit Documentation Feedback

www.ti.com

5 PCB Layout

PCB Layout

Figure 3. Top Layer

Figure 4. Bottom Layer

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

5

C7 = 1 nF R10 = 35.7 k:

2525

=

35.7 k: x 1 nF

fSW =

R10 x C7

= 700 kHz

2525

=

700 kHz x 1 nF

= 35.7 k:

R10 =

fSW x C7

683.0

D

MAX

===

VV

MININO--

V10V5.31 -

V5.31

V

O

175.0

D

MIN

===

VV

MAXINO--

V26V5.31 -

V5.31

V

O

762.0238.01D1'D

=

-

=

-

=

238.0D===

V24V5.31 -

V5.31

V

O

VV

INO

-

:

=

:x

=

x

=

925.2m3259rNr

LEDD

V31.5V5.39VNV

LEDO

=

x

=

x

=

Design Procedure

6 Design Procedure

Refer to LM3429 LM3429Q1 N-Channel Controller for Constant Current LED Drivers (SNVS616) data sheet for design considerations.

6.1 Specifications

N = 9 V

= 3.5V

LED

r

= 325 mΩ

LED

VIN= 24V V

= 10V; V

IN-MIN

fSW= 700 kHz V

= 100 mV

SNS

I

= 1A

LED

Δi

= 250 mA

L-PP

Δi Δv

I

LIM

V V

LED-PP

IN-PP

= 6A

TURN-ON

TURN-OFF

= 17 mA

= 100 mV

IN-MAX

= 10V; V

= 60V; V

HYS

HYSO

www.ti.com

= 27V

= 3V

= 15V

6.2 Operating Point

Solve for VOand rD:

Solve for D, D', D

MAX

, and D

6.3 Switching Frequency

Assume C7 = 1 nF and solve for R10:

The closest standard resistor is actually 35.7 kΩ therefore the fSWis:

The chosen components from step 2 are:

MIN

(1) (2)

:

(3) (4)

(5)

(6)

(7)

(8)

6

AN-1986 LM3429 Boost Evaluation Board SNVA404B–July 2009–Revised May 2013

Submit Documentation Feedback

(9)

DI

LED

x

=

'i

PP-LED

SW

fxrDx

C

O

= =

kHz007925.2 xx:

17.6mA

238.0A1 x

F6.6 P

'i

PP-LED

f

'i

r

SWPP-LEDD

xx

DI

LED

x

CO=

= F84.6 P=

kHz007mA17925.2 xx:

238.0A1 x

C

O

H331L P

=

A31.1

I

12

1

I

RMSL

=

+

x

=

-

I

LED

RMSL

x

=

-

12

1

2

x

+

¸

¸ ¹

·

¨

¨ ©

§

Di

PPL

c

x

'

-

I

LED

D

c

762.0mA247

2

x

¸

¸ ¹

·

¨

¨ ©

§

A1

762.0

A1

PP-==L

DVINx

f1LSWx

kHz007H33 xP

238.0V42 x

mA247

=

'i

==

DVINx

fSWx

238.0V42 x

PH

32.6

=

1L

PP-'iL

kHz007250 mA x

:

k4.21R1

=

:

k1R7R8

==

0.1R9

=

:

LED

= =

k0.11.24V :x

A0.1=

k4.121.0 :x:

R1R9 x

R81.24Vx

1A x 12.4 k: x 0.1:

=

1.24V

= 1.0 k:

I

LED

x R1 x R9

1.24V

:

===

1.0

1A

I

LED

mV100

V

SNS

www.ti.com

6.4 Average LED Current

Solve for R9:

Assume R1 = 12.4 kΩ and solve for R8:

The closest standard resistor for R9 is 0.1Ω and the closest for R8 (and R7) is actually 1 kΩ therefore I is:

The chosen components from step 3 are:

6.5 Inductor Ripple Current

Solve for L1:

The closest standard inductor is 33 µH therefore the actual Δi

L-PP

Design Procedure

(10)

(11)

LED

(12)

(13)

(14)

is:

Determine minimum allowable RMS current rating:

The chosen component from step 4 is:

6.6 Output Capacitance

Solve for CO:

A total value of 6.6 µF (using 3 2.2 µF X7R ceramic capacitors) is chosen therefore the actual Δi

LED-PP

(15)

(16)

(17)

(18)

is:

Determine minimum allowable RMS current rating:

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

(19)

7

1

=

F097.01P==C12

10:

x

sec

rad

M04.1

10:

3P

Zx

1010max(

1P

xZ

=

x

=

,

1Z1P

ZZ

sec

rad

k104

=

sec

rad

M04.110=x

3P

Z

3P

Z

)

F11.0

1

C8 P===

76.1

e5

sec

rad

6

x :

e5

6

2P

xZ

:

= =

sec

rad

76.1=

sec

rad

k52

59005x59005x

1Z

Z

2P

=Z

),min(

1Z1P

ZZ

T50Ux

=T0U= 5900=

04.0A1 :

x

V310762.0

x

RI

LIMLED

x

V310D

x

c

sec

rad

k52===

762.0925.2

2

x:

H33P

Dr

2

D

c

x L1

1Z

Z

sec

rad

k104===

2

F6.6

2.925:

Px

COrDx

2

1P

Z

0.04:R6=

:04.0

===

6.1A

mV245mV245

I

LIM

R6

:=== 041.0

6A

R6

mV245mV245

I

LIM

F2.2C6 = C17 = C19 P=

x

A1

=

I

LED

I

RMSCO-

=

1- 0.683

683.0

1.47A

x

1- D

MAX

D

MAX

=

Design Procedure

The chosen components from step 5 are:

6.7 Peak Current Limit

Solve for R6:

The closest standard resistor is 0.04 Ω therefore I

The chosen component from step 6 is:

6.8 Loop Compensation

ω

is approximated:

P1

LIM

www.ti.com

(20)

(21)

(22)

is:

(23)

(24)

(25)

ω

is approximated:

Z1

(26)

TU0is approximated:

(27)

To ensure stability, calculate ωP2:

(28)

Solve for C8:

(29)

Since PWM dimming can be evaluated with this board, a much larger compensation capacitor C8 = 1.0 µF is chosen.

To attenuate switching noise, calculate ωP3:

(30)

Assume R20 = 10Ω and solve for C12:

(31)

The chosen components from step 7 are:

8

AN-1986 LM3429 Boost Evaluation Board SNVA404B–July 2009–Revised May 2013

Submit Documentation Feedback

D1 o 12A, 100V, DPAK

mW600mV600A1VIP

FDDD

=

x

=

x

=

A1II

LEDMAXD==-

V5.31VV

OMAXRD==-

Q1 o 40A, 100V, DPAK

mW20m50mA640RIP

2

DSON

2

RMSTT

=

:x

=

x

=

-

x

I

RMST=-

I

LED

D

c

=

x

mA640

=

0.238

A1

762.0

D

=

A2.2A1=x

683.01-

683.0

I

MAXT-

V5.31VV

OMAXT==-

C2 = C3 = C16 = C18 = 4.7 PF

mA72

mA250

==

I

RMSIN=-

'i

PP-L

12 12

C

IN

==

kHz700mV100 x

250 mA

F0.45P=

f

'v

SWPPIN-

x

'i

PP-L

x8 x8

F1.0C12 P=

F1.0C8 P=

:10R20=

www.ti.com

6.9 Input Capacitance

Solve for the minimum CIN:

To minimize power supply interaction a much larger capacitance of approximately 20 µF is used, therefore the actual Δv

is much lower. Since high voltage ceramic capacitor selection is limited, four 4.7 µF X7R

IN-PP

capacitors are chosen. Determine minimum allowable RMS current rating:

The chosen components from step 8 are:

6.10 NFET

Determine minimum Q1 voltage rating and current rating:

Design Procedure

(32)

(33)

(34)

(35)

A 100V NFET is chosen with a current rating of 40A due to the low R PT:

The chosen component from step 9 is:

6.11 Diode

Determine minimum D1 voltage rating and current rating:

A 100V diode is chosen with a current rating of 12A and VD= 600 mV. Determine PD:

The chosen component from step 10 is:

= 50 mΩ. Determine I

DS-ON

T-RMS

(36)

(37)

and

(38) (39)

(40)

(41) (42)

(43)

6.12 Input UVLO

Since PWM dimming will be evaluated a three resistor network will be used. Assume R13 = 10 kΩ and solve for R5:

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

(44)

9

R11 = 15.8 k: R18 = 750 k:

=

V

OFFTURN=-

V= 40

R11

k8.15 :

( )

k750k8.151.24V :+:x

(

)

R18

R11

1.24V +x

V

OFFTURN-

:== k15.8

--1.24VV

OFFTURN

x R181.24V

=R11

:x k7501.24V

-1.24V60V

15VA20k750A20

R18

V

HYSO

=

x:

=

x

=

P

===

A

20

15V

R18

P

:k750

V

HYSO

A20

P

k:10R13

=

k:1.43R5

=

k:16.9R4

=

HYS

=

R5

20 PA x 16.9 k: x (1.43 k: + 10 k:)

1.43 k:

HYS

=

+ 20 PA x R

UV2

20 PA x R4 x (R5 + R13)

+ 20 PA x 10 k: = 2.9V

=

16.9 k:

=

20 PA x (1.43 k: + 10 k:)

R4

=

R4

(

)

R5 xx R13

V

HYS

- 20 PA R5

R13+

(

)

20 PA

x

(

:

)

x k10k1.43

2.9V - 20 PA

: x

R5

(

)

R13R51.24V +x

V

ONTURN=-

= V9.91=

( )

k10k1.431.24V :+:x

k1.43 :

V

ONTURN-

:== k1.43

--1.24VV

ONTURN

x R131.24V

=

R5

:x k101.24V

-1.24V10V

Design Procedure

The closest standard resistor is 1.43 kΩ therefore V

Solve for R4:

The closest standard resistor is 16.9 kΩ making V

The chosen components from step 11 are:

TURN-ON

:

HYS

www.ti.com

(45)

is:

(46)

(47)

(48)

6.13 Output OVLO

Solve for R18:

The closest standard resistor is 750 kΩ therefore V

Solve for R11:

The closest standard resistor is 15.8 kΩ making V

The chosen components from step 12 are:

HYSO

TURN-OFF

(49)

(50)

is:

(51)

(52)

:

(53)

(54)

10

AN-1986 LM3429 Boost Evaluation Board SNVA404B–July 2009–Revised May 2013

Submit Documentation Feedback

V

DIM

(V)

V

DIM

4 ms/DIV

I

LED

I

LED

(A)

10

5

0

1.0

0.0

-1.0

I

LED

(A)

V

SW

(V)

40

20

0

1.0

0.5

0.0

I

LED

V

SW

2 Ps/DIV

www.ti.com

7 Typical Waveforms

TA= +25°C, VIN= 24V and VO= 31.5V.

Figure 5. Standard Operation Figure 6. 200Hz 50% PWM Dimming

TP1 Switch Node Voltage (VSW) TP11 Dim Voltage (V

LED Current (I

8 Alternate Designs

Alternate designs with the LM3429 evaluation board are possible with very few changes to the existing hardware. The evaluation board FETs and diodes are already rated higher than necessary for design flexibility. The input UVLO, output OVP, input and output capacitance can remain the same for the designs shown below. These alternate designs can be evaluated by changing only R9, R10, and L1.

Table 1 gives the main specifications for four different designs and the corresponding values for R9, R10,

and L1. PWM dimming can be evaluated with any of these designs.

) LED Current (I

LED

Typical Waveforms

)

DIM

)

LED

Table 1. Alternate Design Specifications

Specification / Design 1 Design 2 Design 3 Design 4 Component

V

IN

V

O

f

SW

I

LED

R9 0.05Ω 0.2Ω 0.04Ω 0.08Ω R10 41.2 kΩ 35.7 kΩ 49.9 kΩ 35.7 kΩ L1 22µH 68µH 15µH 33µH

10V 15V 20V 25V 14V 21V 28V 35V 600kHz 700kHz 500kHz 700kHz 2A 500mA 2.5A 1.25A

SNVA404B–July 2009–Revised May 2013 AN-1986 LM3429 Boost Evaluation Board

Submit Documentation Feedback

11

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed.

TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide adequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions.

Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.

Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications.

In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms.

No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use.

Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use.

TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

Products Applications

Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265

Texas Instruments Incorporated AN-1986 User's Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

1 Introduction

2 Schematic

3 Pin Descriptions

4 Bill of Materials

5 PCB Layout

6 Design Procedure

6.1 Specifications

6.2 Operating Point

6.3 Switching Frequency

6.4 Average LED Current

6.5 Inductor Ripple Current

6.6 Output Capacitance

6.7 Peak Current Limit

6.8 Loop Compensation

6.9 Input Capacitance

6.10 NFET

6.11 Diode

6.12 Input UVLO

6.13 Output OVLO

7 Typical Waveforms

8 Alternate Designs