Diodes AL8812 User Manual

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.

GATE

INPUT

VCC

SENSE

DRIVE

U-DFN6040-12

Applications

• Low Voltage LED Lighting such as MR-16

• General Purpose DC-DC Converter

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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Pin Descriptions

L8812

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

Number

(U-DFN6040-12)

Current drive collector: Normally connected to V

Function

directly or via a resistor.

Functional Diagram

D RIVE

SW/C

SENSE

VCC

INPUT

GATE

AL8812

Document number: DS37099 Rev. 1 - 2

Ipk

Oscillato

Comparato



100

1.25V

Reference

Regulato

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SW/ E

TIMING

GND

DRAIN

SOURCE

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Absolute Maximum Ratings (@T

= +25°C, unless otherwise specified.)

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

CE (switch)

Switch Emitter Voltage (V

Switch Collector to Emitter Voltage 36 V

1 = 40V)

36 V

DRIVE Driver Collector Voltage 36 V

C (driver)

ISW

VDS

VGS

SOURCE

θJA

θJC

TMJ

TOP

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.)

Symbol Characteristics Min Typ Max Unit

OSCILLATOR

Frequency (V

osc

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

chg

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

dischg

/ I

dischg

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)

= 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)

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)

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

GS(th)

VFD

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

mΩ mΩ

March 2014

Performance Characteristics

Figure 1. Vce(sat) versus le

1.4

L8812

Figure 2. Reference Voltage versus Temp.

1.26

1.2

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)

1.55

1.45

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

1.7 T

=25oC

≤10W

Pin2=5

1.6

1.5

1.4

100 300 500 700 900 1100 1300 1500

AL8812

Document number: DS37099 Rev. 1 - 2

(mA)

1000

100

, Output Switch On-Off Time(us)

on-off

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Figure 6.Output Switch On-Off Time versus

Oscillator Timing Capacitor

= 5.0V

Pin 7 = V

Pin 5 = GND T

= 25oC

0.1

0.01 0.1 1 10

CT, Oscillator Timing Capacitor (

off

nF)

March 2014

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