MOTOROLA MC33441DTBEL, MC33441DTBR2 Datasheet

 Semiconductor Components Industries, LLC, 2000

April, 2000 – Rev. 1

1 Publication Order Number:

MC33441/D

MC33441

Electroluminescent Lamp Driver IC

3.5V and is capable to supply a typical 140Vpp AC output voltage. The standby current of the device is typically 10nA which is ideal for low power portable products. Externally, one inductor and one resistor are needed to generate the desirable voltage charge and to fine tune the oscillator’s frequency. This device is offered in 8–Pin TSSOP miniature package. The operating temperature is –20°C to 70°C.

Features:

• Battery Operation 1.8V – 3.5V

• Typical Voltage Output 140Vpp

• Typical Standby Current 10nA

• Internal Oscillator with External Tuning Resistor

• Enable Control Pin with a 300K Internal Pull–Down Resistor

• 8–Pin TSSOP Package (Thickness = 1.05mm, Width = 4.5mm,

Length = 3.1mm & Lead Pitch = 0.65mm)

Types of Applications:

• Pagers, Cellular Phones, Portable CD Players/Minidisks

• Databanks, Calculators

Simplified Block Diagram

FREQUENCY

DIVIDER

VDD

ENB

RT1

OSC

VSS

H–BRIDGE

COIL

DRIVER

COIL

EL1

EL2

FILTER

COIL

Device Package Shipping

ORDERING INFORMATION

MC33441DTBR2 TSSOP–8 2500 Units / Reel

TSSOP–8

DTB SUFFIX

CASE 948J

http://onsemi.com

PIN CONNECTIONS AND

MARKING DIAGRAM

VSS COIL

FILTER

(Top View)

ENB

RT1

VDD

EL2

EL1

M33

441

ALY

A = Assembly Location L = Wafer Lot Y = Y ear W = Work Week

MC33441

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Figure 1. Test Circuit

H–BRIDGE

VSS

ENB

RT1

OSC

FREQ.

DIVIDER

VDD

COIL DRIVER

EL LAMP

AND2

EL1

EL2

FILTER

COIL

AND2

INDUCTOR

FILTER

EXT

Battery / V

OPTIONAL

MAIN SWITCH

PIN FUNCTION DESCRIPTION

Pin No.

(TSSOP–8)

Name Description

Pin 1

VDD

ББББББББББББББББББББББ

Input voltage supply

Pin 2

ENB

ББББББББББББББББББББББ

Enable the whole device to operate

Pin 3

RT1

ББББББББББББББББББББББ

Internal oscillator’s fine tuning resistance input

Pin 4

VSS

ББББББББББББББББББББББ

Analog/Power ground

Pin 5

COIL

ББББББББББББББББББББББ

Coil/Inductance input

Pin 6

Filter

ББББББББББББББББББББББ

EL Filter

Pin 7

EL2

ББББББББББББББББББББББ

EL lamp driver output 2

Pin 8

EL1

ББББББББББББББББББББББ

EL lamp driver output 1

MC33441

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MAXIMUM RATINGS (T

= 25°C, unless otherwise noted.)

Rating

Symbol Max Unit

Power Supply Voltage

7.5

ББББББББББББ

Digital Input Voltage Range

ÁÁ

LOGIC = 0 LOGIC = 1

ÁÁÁ

0.5

Operating Junction Temperature

J(max)

150

°C

Operating Ambient Temperature

–20 to +70

°C

Storage Temperature Range

stg

–50 to +150

°C

Power Dissipation

300

Thermal Resistance, Junction–to–Air

θJA

178

°C/W

DC ELECTRICAL CHARACTERISTICS (V

= 2.65V , TA = 25°C, Lamp Capacitance = 2.2nF, Coil = 1mH unless

otherwise noted.)

Characteristic

Symbol Min Typ Max Unit

Supply Voltage

1.8

–

3.5

Output Voltage (1.8V < VDD ≤ 3.5 V)

120

140

160

Peak Coil Current (1.8V < VDD ≤ 3.5 V)

COIL

–

150

Average Coil Current from Battery (1.8V < VDD ≤ 3.5 V)

VDD

–

mA dc avg

Standby Current (VDD = 3.0 V, ENB = 0)

STAND

–

100

Clock Frequency (R

EXT

= 125KW)

osc

112

140

168

kHz

Lamp Drive Frequency (F

osc

Divide by 384)

–

364.6

–

Coil Drive Frequency ( F

osc

Divide by 4)

COIL

–

kHz

Coil Drive Clock Duty Cycle

COIL

–

EL Lamp Capacitance Range

–

2.2

–

EL1

TIME

EL2

TIME

Typical Vpp = 140V

(160V max)

Figure 2. Output Waveform

MC33441

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Figure 3. Output Waveform vs. Time

VDD = 2.65V Lamp Freq. = 365Hz EL Lamp = 2.2nF

X = 1ms/div, Y = 50V/div

OPERA TING DESCRIPTION

General

The MC33441 is a DC–AC inverter integrated circuit for driving EL lamps. It can boost the supply voltage to the level required by EL lamps and also provide high voltage AC lamp excitation. It consists of an oscillator, a frequency divider, a coil driving circuit and a switched H–bridge network. The input supply voltage range is from 1.8V to 3.5V and is capable to supply a typical 140Vpp AC output voltage. The standby current of the device is typically 10nA which is ideal for low power portable products. Externally, one inductor and one resistor are needed to generate the desirable voltage charge and to fine tune the oscillator’s frequency. This device is offered in 8–Pin TSSOP packages. The operating temperature is –20°C to 70°C.

Oscillator and Frequency Divider

Two circuits are put together to form the oscillator. They are Vref and Ibias. The functionality of Vref block is to generate a zero temperature coefficient (TC) voltage reference which is about 1.27V. This 1.27V will then be used in Ibias circuit to provide current biasing to all of the internal circuits with the value equal to Vref divided by an internal resistor. Besides of that, an external resistor is also connected to this circuit block for setting the oscillator’s frequency. The temperature coefficient is dominated by the value of that resistor. Therefore, if a low TC resistor is used, the oscillator frequency’s TC can be kept low.

The current mirrors with the induced current equal to the Vref divided by an external resistor are used to charge and discharge an internal capacitor to provide a 50% duty cycle clock signal. This original clock pulse will then be fed into the frequency divider which will generate two additional clock signals with different frequency and duty cycle to the coil–driver and the H–bridge circuits. The oscillator frequency is governed by the following equation:

OSC

6 R

EXT

INT

HzǓ+

1.667 10

EXT

COIL

= F

OSC

B 4

FEL = F

OSC

B 384

where C

INT

is about 10pF.

Coil Driver

The coil driver is basically a simplified boost converter. It takes a higher frequency clock signal from the frequency divider to turn on/off the main switch alternatively. When the main switch is on, current will flow through the coil to ground. Once the switch is being turned off, the energy stored in the coil will be released to the external capacitor (EL lamp) through an internal diode. According to the frequency of the clock signals between the coil driver and the H–bridge, the external capacitor (EL lamp) will be charging to the desirable level.

Current limit circuit (typical 70mA & max. 150mA) is implemented in this device. Since the current through the coil will increase corresponding to the input voltage, if the input voltage is high and the inductance of the coil is small, the coil can be saturated. The current limit feature is used to avoid this happen. The main switch is parallel to a much smaller switch which has their collector and their base connected together. However, the emitter of the smaller switch is tied to a sensing resistor while the emitter of the main switch is connected to ground. The coil current will split into two according to the sizing ratio between the main and the smaller switch. The current through the smaller switch will also flow through the sensing resistor and generates a voltage. If the voltage across this sensing resistor is above the pre–set value, then both switches

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