Diodes AL8811 User Manual

A

L8811

Boost/Buck/Inverting DC-DC CONVERTER

Description

The AL8811 is a monolithic control circuit containing the primary

functions required for DC-to-DC converters. 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. This series is specifically designed for

incorporating in Boost, Buck and voltage-inverting applications with a

minimum number of external components.

Pin Assignments



Features

 Operation from 3.0V to 20V Input

 Low Standby Current

 Current Limiting

 Output Switch Current to 1.6A

 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.

Applications

 Low Voltage LED Lighting such as MR-16

 General Purpose DC-DC Converter

MSOP-8

Typical Application Diagram

Electronic Transformer compatible MR16 lamp Simplified Schematic

AL8811

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Pin Descriptions

Pin Name Pin Number Descriptions

Current

Switch+

Current
Switch-

CT 3 Timing Capacitor to control the switching frequency

GND 4

Feedback 5 Feedback pin for inverting input of internal comparator

VCC 6 Supply voltage pin

Current

Sense

Current

Drive

1

2

7

8

Internal switch transistor collector:
Connect to Inductor for boost converter.
Connect to VCC for Buck or Inverting converter
Internal switch transistor emitter:
Connect to GND for boost converter
Connect to Inductor for buck or inverting converter

Peak Current Sense Input by monitoring the voltage drop across an external current sense
resistor to limit the peak current through the switch
Current drive collector:
Normally connected to VCC directly or via a resistor.

L8811

Functional Diagram

AL8811

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L8811

Absolute Maximum Ratings (@T

= +25°C, unless otherwise specified.)

A

Symbol Parameter Rating Unit

VCC

VIR

V

C (SWITCH)

V

E (SWITCH)

V

CE (SWITCH)

V

C (DRIVER)

I

C (DRIVER)

ISW

PD

JA

TMJ

T

STG

Power Supply Voltage 20 V

Comparator Input Voltage Range -0.3 to +36 V

“Current Switch +” Collector Voltage 36 V

„Current Switch –„ Emitter Voltage (V

“Current Switch” Collector to Emitter Voltage 36 V

“Current Drive” Collector Voltage 36 V

1 = 36V)

PIN

36 V

“Current Drive” Collector Current 100 mA

“Current Switch” Current 1.6 A

Power Dissipation (Note 4) 600 mW

Thermal Resistance 130

Maximum Junction Temperature +150

Storage Temperature Range -65 to +150

C/W

C

C

ESD HBM Human Body Model ESD Protection 1 kV

ESD MM Machine Model ESD Protection 150 V

Caution: Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only;

Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling

functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. Device reliability may be
affected by exposure to absolute maximum rating conditions for extended periods of time.

and transporting these devices.

Recommended Operating Conditions

Symbol Parameter Min

Max

Unit

VCC Supply Voltage 3 20 V
TOP

Operating Junction Temperature Range

-40

Electrical Characteristics (@ V

= 5V, TA = +25°C, unless otherwise specified.)

CC

Symbol Parameter Min Typ Max Unit

OSCILLATOR

f

OSC

I

CHG

I

DISCHG

I

DISCHG

V

IPK (SENSE)

Frequency (V

5 = 0V, CT = 1.0nF, TA = +25°C)

PIN

Charge Current (VCC = 5.0V to 20V, TA = +25°C)

Discharge Current (VCC = 5.0V to 20V, TA = +25°C)

/ I

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

CHG

Current Limit Sense Voltage (I

CHG

= I

DISCHG

, TA = +25°C)

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 4)

V

CE(sat)

V

CE(sat)

Saturation Voltage, Darlington Connection
(I

= 1.0A, Pins 1, 8 connected)

SW

Saturation Voltage, Darlington Connection
(I

= 1.0A, ID = 50mA, Forced ß  20)

SW

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

I

Collector Off-State Current (VCE = 20V)

C(off)

— 1.0 1.3 V

— 0.45 0.7 V

50 75 — —

— 0.01 100 µA

COMPARATOR

Vth Threshold Voltage TA = +25°C

Reg

Threshold Voltage Line Regulation (VCC = 3.0V to 20V)

(LINE)

1.225 1.25 1.275 V

— 1.4 6.0 mV

TOTAL DEVICE

ICC

Supply Current (V

> Vth Pin 2 = Gnd, remaining pins open)

V

PIN 5

= 5.0V to 20V, CT =1.0nF, Pin 7 = VCC,

CC

— 3.5 mA

—

AL8811

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C

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Typical Performance Characteristics

Figure 1. Vce(sat) versus le

1.4

L8811

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 102030 40 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

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

1.7
T

=25oC

A

10W

Pin2=5

1.65

( sat), (V)

1.6

CE

V

1.55

1.5

1.45

1.4

100 300 500 700 900 1100 1300 1500

AL8811

Document number: DS36090 Rev. 2 - 2

I

E

(mA)

1000

100

10

, Output Switch On-Off Time(us)

on-off

t

0.1

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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

1

0.01 0.1 1 10

CT, Oscillator Timing Capacitor (

t

on

t

off

nF)

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June 2013