Diodes AL8812 User Manual

A

Description

L8812

BOOST/BUCK DC-DC CONVERTER FOR DIMMABLE MR16 LED LAMPS

Pin Assignments

The AL8812 is a monolithic control circuit containing the primary

functions required for DC-to-DC converters with MOSFET in one

package. These devices consist of an internal temperature

compensated reference, comparator, controlled duty cycle oscillator

with an active current limit circuit, driver and high current output

switch. Additionally a 60V, 3.6A MOSFET is integrated for reduced

BOM cost and size. This series is specifically designed for buck and

boost applications with a minimum number of external components.

Features

• Operation from 3.0V to 20V Input

• Integrated 60V, 3.6A MOSFET

• Low Standby Current

• Current Limiting

• Output Voltage Adjustable

• Frequency Operation to 100 kHz

• Precision 2% Reference

• Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

• Halogen and Antimony Free. “Green” Device (Note 3)

Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.

2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.

3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.

NC

GATE

INPUT

1

2

3

4

VCC

SENSE

DRIVE

5

6

U-DFN6040-12

Applications

• Low Voltage LED Lighting such as MR-16

• General Purpose DC-DC Converter

12

11

10

9

8

7

DRAIN

SOURCE

TIMING

GND

SW/E

SW/C

Typical Applications Circuit

(For detailed schematic please contact your Diodes Sales Representative)

AL8812

Document number: DS37099 Rev. 1 - 2

Dimmable MR-16 LED Driver System Diagram

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r

r

r

_

Pin Descriptions

L8812

Pin

Name

NC 1 No Connection

GATE 2 Gate connection of internal MOSFET.

INPUT 3 Feedback pin for inverting input of internal comparator

VCC 4 Supply voltage pin

SENSE 5 No Connection.

DRIVE 6

SW/C 7 Internal switch transistor collector

SW/E 8 Internal switch transistor emitter

GND 9 Ground Connection

TIMING 10 Timing Capacitor to control the switching frequency.

SOURCE 11 Source connecton of internal MOSFET

DRAIN 12 Drain connection of internal MOSFET

Exposed PAD1 Exposed Pad of MOSFET Drain

Exposed PAD2 Exposed Pad of AL8812 and connect to PCB ground

Pin

Number

(U-DFN6040-12)

Current drive collector:
Normally connected to V

Function

directly or via a resistor.

CC

Functional Diagram

D RIVE

6

7

SW/C

SENSE

VCC

INPUT

GATE

5

4

AL8812

Document number: DS37099 Rev. 1 - 2

S

Q

R

Ipk

Oscillato

3

2

C

Comparato

+



T

100

1.25V

Reference

Regulato

Q2

Q1

8

10

9

12

11

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SW/ E

TIMING

GND

DRAIN

SOURCE

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Absolute Maximum Ratings (@T

= +25°C, unless otherwise specified.)

A

Symbol Parameter Value Unit

VCC

VIR

Power Supply Voltage 20 V

Comparator Input Voltage Range -0.3 to +36 V

SW/C Switch Collector Voltage 36 V

SW/E

V

CE (switch)

Switch Emitter Voltage (V

Switch Collector to Emitter Voltage 36 V

1 = 40V)

Pin

36 V

DRIVE Driver Collector Voltage 36 V

I

C (driver)

ISW

VDS

VGS

I

SOURCE

PD

θJA

θJC

TMJ

TOP

T

stg

Driver Collector Current (Note 4) 100 mA

Switch Current 1.6 A

Maximum MOSFET Drain-Source voltage 60 V

Maximum MOSFET Gate-Source voltage +/-20 V

Maximum Continuous Source (Body Diode) Current 3.7 A

Continuous Power Dissipation (TA = +25°C)
(U-DFN6040-12 (derate 10mW/°C above +25°C)

1000 mW

Junction-to-Ambient Thermal Resistance 47.31

Junction-to-Case Thermal Resistance 6.42

Maximum Junction Temperature +150

Operating Junction Temperature Range

0 to +105

Storage Temperature Range -65 to +150

ESD HBM Human Body Model ESD Protection 250 V

ESD MM Machine Model ESD Protection 100 V

Note: 4. Maximum package power dissipation limits must be observed.

Electrical Characteristics (@T

= +25°C, unless otherwise specified.)

A

Symbol Characteristics Min Typ Max Unit

OSCILLATOR

f

Frequency (V

osc

I

Charge Current (VCC = 5.0V to 40V, TA = +25°C)

chg

I

Discharge Current (VCC = 5.0V to 40V, TA = +25°C)

dischg

I

/ I

dischg

V

ipk (sense)

Discharge to Charge Current Ratio (Pin 7 to VCC, TA = +25°C)

chg

Current Limit Sense Voltage (I

5 = 0V, CT = 1.0nF, TA = +25°C)

PIN

= I

chg

, TA = +25°C)

dischg

24 33 42 kHz

24 30 42 μA

140 200 260 μA

5.2 6.5 7.5 —

300 400 450 mV

OUTPUT SWITCH (Note 5)

V

CE (sat)

V

CE (sat)

Saturation Voltage, Darlington Connection
(ISW = 1.0A, Pins 1,8 connected)

Saturation Voltage, Darlington Connection
(ISW = 1.0A, ID = 50mA, Forced ß ≈ 20)

hFE DC Current Gain (ISW = 1.0A, VCE = 5.0V, TA = +25°C)

I

Collector Off-State Current (VCE = 40V)

C (off)

— 1.0 1.3 V

— 0.45 0.7 V

50 75 — —

- 0.01 100 μA

OUTPUT MOSFET

V

GS(th)

VFD

R

DS(ON)

MOSFET Gate Threshold voltage 1 — 2.2 V

MOSFET Diodes forward voltage — .85 .95 V

Drain-source on-resistance (VGS = 10V, ID = 2.5A)
Drain-source on-resistance (VGS = 4.5V, ID = 2A)

— —

120
180

COMPARATOR

Vth

— 1.225 1.25 1.275 —

— 1.21 — 1.29 —

Reg

line

Threshold Voltage
TA = +25°C
TA = 0oC to +70oC

Threshold Voltage Line Regulation (VCC = 3.0V to 40V)

— — — V

— 1.4 6.0 mV

TOTAL DEVICE

ICC

Note: 5. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient temperature as possible.

Supply Current (VCC = 5.0V to 40V, CT =1.0nF, Pin 7 = VCC, V
= Gnd, remaining pins open)

> Vth Pin 2

Pin 5

— — 3.5 mA

AL8812

Document number: DS37099 Rev. 1 - 2

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L8812

°C/W

°C/W

°C

°C

°C

mΩ
mΩ

March 2014

A

Performance Characteristics

Figure 1. Vce(sat) versus le

1.4

L8812

Figure 2. Reference Voltage versus Temp.

1.26

1.2

1

0.8

Vce(sat), Saturation Voltage (V)

0.6
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Ie, Emitter Current (A)

Figure 3. Current Limit Sense Voltage

versus Temperature

440

420

400

380

360

Current Sense Voltage (mV)

340

320

0 1020 3040 50 6070 8090100

Temperature (oC)

1.255

1.25

Reference Voltage (V)

1.245

1.24
0 102030405060708090100

Temperature (oC)

Figure 4. Standby Supply Current

versus Supply Voltage

4.0

3.5

3.0

2.5

2.0

1.5

1.0

Icc, Supply Current (mA)

0.5

0.0
0 5 10 15 20 25 30 35 40

Vcc, Supply Voltage (V)

Figure 5. Emitter Follower Configuration

Output Saturation Voltage vs. Emitter Current

1.8

1.75

1.65

( sat), (V)

CE

V

1.55

1.45

Vcc=2~10V
Pin1,7,8=Vcc
Pin3,5=GND

1.7
T

=25oC

A

≤10W

Pin2=5

1.6

1.5

1.4

100 300 500 700 900 1100 1300 1500

AL8812

Document number: DS37099 Rev. 1 - 2

I

E

(mA)

1000

100

, Output Switch On-Off Time(us)

on-off

t

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Figure 6.Output Switch On-Off Time versus

Oscillator Timing Capacitor

V

= 5.0V

CC

Pin 7 = V

CC

Pin 5 = GND
T

= 25oC

A

10

1

0.1

0.01 0.1 1 10

CT, Oscillator Timing Capacitor (

t

on

t

off

nF)

© Diodes Incorporated

March 2014

A

L8812

T = 25°C

10

1

0.1

Drain Current (A)

D

I

0. 1 1 10

VDS Drain-Source Voltage (V)

10V 5V

4V

3.5V

3V

V

GS

2.5V

Output Characteristics

10

VDS = 10V

T = 150°C

1

T = 25°C

Drain Current (A)

0.1

D

I

23 45

VGS G a te -So urce V o ltage (V)

Typical Transfer Characte ristics

T = 150°C

10

1

0.1

Drain Current (A)

D

I

0.1 1 10

VDS Dr ain-So urc e V oltag e ( V)

10V

5V

Output Characteristics

1.8

GS(th)

1.6

1.4

and V

1.2

DS (on )

1.0

0.8

0.6

0.4

-50 0 50 100 150

Normali sed R

Tj Junction Temperature (°C)

VGS = 10V

ID = 2.5A

VGS = V

DS

ID = 250uA

R

V

Normalised Curves v Temperature

DS(on)

GS( th)

4V

3.5V

3V

2.5V

V

GS

2V

1

3V

0.1

T = 25°C

Drain-Source On-Resistance (W)

On-Resistance v Drain Current

DS( o n)

R

3.5V

110

ID Dr ain Cu rre nt (A )

4V

50 0

40 0

30 0

20 0

C

ISS

C

OSS

C

RSS

10 0

C Capacitance (pF)

0

110

VDS - Drain - Source Voltage (V)

4.5V

V

GS

5V

10V

VGS = 0V

f = 1MHz

10

1

T = 150°C

T = 25°C

0.1

Reve r se Dr ai n Cu rr ent (A )
I

0.4 0.6 0.8 1.0 1.2

SD

VSD Source-Drain Voltage (V)

Source-Drain Diode Forward Voltage

10

ID = 2 .5A

8

6

4

2

Gate-Source Voltage (V)

0

0123456

GS

V

Q - Charge (nC)

VDS = 30V

AL8812

Document number: DS37099 Rev. 1 - 2

Gate-Source Voltage v Gate ChargeCapacitance v Drain-Source Voltage

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L8812

Typical Application Circuits

Circuits shown below represent connections employed for different topologies. To use the integrated MOSFET the typical configuration below
can be used.

DRIVE

SW/C

SW/E

AL8812

AL8812

Document number: DS37099 Rev. 1 - 2



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GATE

DRAIN

SOURCE

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Typical Application Circuits (cont.)

Boost Converter

L8812

Test Conditions Results

Line Regulation

Load Regulation

Output Ripple

Efficiency

AL8812

Document number: DS37099 Rev. 1 - 2

Vin = 9V to 12V, IO = 200mA

Vin = 12V, IO = 50mA to 200mA

Vin = 12V, IO = 200mA 500mVPP

Vin = 12V, IO = 200mA

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20mV = ±0.035%

15mV = ±0.035%

80%

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Typical Application Circuits (cont.)

Buck Converter

L8812

Test Conditions Results

Line Regulation

Load Regulation

Output Ripple

Efficiency

AL8812

Document number: DS37099 Rev. 1 - 2

Vin = 12V to 24V, IO = 500mA

Vin = 24V, IO = 50mA to 500mA

Vin = 24V, IO = 500mA 160mVPP

Vin = 24V, IO = 500mA

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20mV = ±0.2%

5mV = ±0.05%

82%

March 2014

© Diodes Incorporated

A

)

)

t

)

5

5

p

)

)

pk (

)

pk (

)

)

)

pk (

)

pk (

)

pk (

)

(pp)

(pp)

L8812

Design Formula Table

Calculation Boost Buck

V

+ VF -V

tON / t

( tON + t

off

)

off

OUT

V

- V

IN (min

1/f 1/f

tON + t

t

off

tON ( tON +t

CT

I

(switch) 2I

k

tON

t

t

OFF

OFF

4.0×10
(tON / t

OUT (max

Rsc 0.3 / I

L

(min)

CO

V

= Saturation voltage of the output switch.

sat

V

= Forward voltage drop of the output rectifier.

F

( V

9

IN (min

I

– V

sat

I

switch

I

V

The following power supply characteristics must be chosen:

- Nominal input voltage.

V

IN

- Desired output voltage, |V

V

OUT

I

- Desired output current.

OUT

- Minimum desired output switching frequency at the selected values of Vin and Io.

f

min

V

- Desired peak-to-peak output ripple voltage. In practice, the calculated capacitor value will need to be increased due to its

ripple(pp)

| = 1.25 (1+R2/R1)

OUT

equivalent series resistance and board layout. The ripple voltage should be kept to a low value since it will directly affect the line and
load regulation.

V

IN (min

V

sa

tON + t

OFF

+1

) - t

( tON +t

OFF

-

tON 4.0×10

+1) 2I

off

0.3 / I

switch

)

t

on (max)

I

OUT tON

8V

ripple

( V

tON

OFF

IN(min

IN(min

– V

switch

switch

+ vF

OUT

- V

SAT

OFF

) - t

OFF

-

OUT(max

switch

-V

SAT

( t

OFF

ripple

- V

OFF

tON

)

OUT

+ tON )

OUT

+1

ON (max)

AL8812

Document number: DS37099 Rev. 1 - 2

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Ordering Information

Tube 13” Tape and Reel

Part Number Package Code Packaging

AL8812FDF-13 FDF U-DFN6040-12 NA NA 3000/Tape & Reel -13

Quantity

Part Number

Suffix

Quantity

Marking Information

(1) U-DFN6040-12

L8812

Part Number

Suffix

Package Outline Dimensions (All dimensions in mm.)

Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version.

A

E

E1

AL8812

Document number: DS37099 Rev. 1 - 2

D1

D

D2

Z

A1

e

E2

b

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A3

Seating Plane

L

U-DFN6040-12

Dim Min Max Typ

A 0.55 0.65 0.60
A1 0 0.05 0.02
A3 - - 0.15

b 0.35 0.45 0.40

D 5.95 6.05 6.00
D1 1.95 2.15 2.05
D2 2.35 2.55 2.45

e - - 1.00

E 3.95 4.05 4.00
E1 2.10 2.30 2.20
E2 1.80 2.00 1.90

L 0.35 0.45 0.40

Z - - 0.30

All Dimensions in mm

March 2014

© Diodes Incorporated

A

L8812

Suggested Pad Layout

Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.

DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).

Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes
without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the
application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or
trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume
all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated
website, harmless against all damages.

Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or
indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.

Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings
noted herein may also be covered by one or more United States, international or foreign trademarks.

This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.

Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:

A. Life support devices or systems are devices or systems which:

1. are intended to implant into the body, or

labeling can be reasonably expected to result in significant injury to the user.

B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.

Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.

Copyright © 2014, Diodes Incorporated

www.diodes.com

Y1

X1

Pin1

2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the

AL8812

Document number: DS37099 Rev. 1 - 2

X3

C

X2

X

Y

G

Y3

Y2

G1

IMPORTANT NOTICE

LIFE SUPPORT

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Dimensions

C 0.500
G 0.650

G1 0.350

X 0.250
X1 1.075
X2 1.275
X3 2.750

Y 0.400
Y1 1.150
Y2 1.000
Y3 2.300

Value

(in mm)

March 2014

© Diodes Incorporated