SP4490UEB

® SP4490 Two Panel Electroluminscent Lamp Driver s Single IC Drives 2 EL Lamps Independently For Backlighting: • Cell Phone Keypad & LCD • Multi-Color EL Lamps • Multi-Segment EL Lamps s Control Over Lamp-A & Lamp-B For Independent Operation s +2.2V to +6.0V Battery Operation s Single Coil Used To Generate High Voltage AC Outputs s Low Power Standby Mode Draws 100nA Typical Current s A Single Resistor Controls the Internal Oscillator s DC-AC Inverter Produces Up To 220VPP s Space-Saving 10µSOIC Package DESCRIPTION The SP4490 electroluminescent lamp driver provides designers of cell phones PDA's and other handheld, portable electronic devices with an integrated solution for driving two EL lamps independently. The SP4490 reduces system cost, component count and board space requirements over a discrete 2-EL driver approach. The EL lamps operate in opposite phase so the SP4490 can be easily implemented in applications driving multi-color or multi-segment EL lamps. The SP4490 operates from a +2.2V to +6.0V battery source. The device features a low power standby mode which draws less than 1µA. The frequency of the internal oscillator is set using a single external resistor. A single external inductor is required to generate the high voltage AC outputs to drive the EL lamps. All input pins are ESD protected with internal diodes to VDD and VSS. APPLICATIONS s Cellular Phones s PDA's s Handheld GPS Units s Security Systems s POS Terminals EL1/EL2 VDD ROSC ON/OFF VSS 1 2 3 4 5 SP4490 10 9 8 7 6 EL1 EL2 ELcommon CAP COIL Rev. 9/12/00 SP4490 Two Panel Electroluminescent Lamp Driver © Copyright 2000 Sipex Corporation 1 ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. Power Supply, VDD.................................................7.0V Input Voltages, Logic.....................-0.3V to (VDD+0.3V) Lamp Outputs...................................................220VP-P Operating Temperature.........................-40˚C to +85˚C Storage Temperature..........................-65˚C to +150˚C Power Dissipation Per Package 10-pin µSOIC (derate 8.84mW/˚C above +70˚C)....................720mW STORAGE CONSIDERATIONS Storage in a low humidity environment is preferred. Large high density plastic packages are moisture sensitive and should be stored in Dry Vapor Barrier Bags. Prior to usage, the parts should remain bagged and stored below 40°C and 60%RH. If the parts are removed from the bag, they should be used within 48 hours or stored in an environment at or below 20%RH. If the above conditions cannot be followed, the parts should be baked for four hours at 125°C in order remove moisture prior to soldering. Sipex ships product in Dry Vapor Barrier Bags with a humidity indicator card and desiccant pack. The humidity indicator should be below 30%RH. The information furnished by Sipex has been carefully reviewed for accuracy and reliability. Its application or use, however, is solely the responsibility of the user. No responsibility for the use of this information become part of the terms and conditions of any subsequent sales agreement with Sipex. Specifications are subject to change without no responsibility for any infringement of patents or other rights of third parties which may result from its use. No license or other proprietary rights are granted by implication or otherwise under any patent or patent rights of Sipex Corporation. SPECIFICATIONS VDD = +3.0V, L = 470µH, CLAMP = 8nF, ROSC = 464kΩ, and TAMB = 25˚C unless otherwise noted. PARAMETER Supply Voltage, VDD Supply Current, IDD Coil Voltage, VCOIL Shutdown Current, ISD = ICOIL + IDD ELEN Input Voltage, VELEN LOW HIGH Input Resistance EL1/EL2 and ON/OFF INDUCTOR DRIVE Coil Frequency, fCOIL Coil Duty Cycle Coil Current, ICOIL Peak Coil Current, IPK-COIL EL LAMP OUTPUT EL Lamp Frequency, fLAMP Peak to Peak Output Voltage, VPK-PK MIN. 2.2 TYP. 3.0 1.4 MAX. 6.0 4.0 UNITS V mA V LCOIL= 470µH CONDITIONS VDD 1 µA VELEN = 0V 2.75 0 3.0 0.25 V 1 MΩ 45 40 57 70 73 kHz % TAMB = +25OC TAMB = -40OC to +85OC 90 39 74 60 100 mA mA Guaranteed by design 350 312 138 130 450 550 570 Hz TAMB = +25OC TAMB = -40OC to +85OC TAMB = +25OC TAMB = -40OC to +85OC © Copyright 2000 Sipex Corporation 170 V Rev. 9/12/00 SP4490 Two Panel Electroluminescent Lamp Driver 2 PINOUT EL1/EL2 VDD ROSC ON/OFF VSS 1 2 3 4 5 SP4490 10 9 8 7 6 EL1 EL2 ELcommon CAP COIL PIN ASSIGNMENTS Pin 1 — EL1/EL2 — Electroluminescent Lamp Output Select. Selects either EL1 Output when input is LOW or EL2 Output when input is HIGH. Pin 2 — VDD — Positive Battery Power Supply. This pin should be bypassed with a 0.1µF capacitor. Pin 3 — ROSC — Oscillator Resistor. Connecting a resistor between this pin and VDD sets the frequency of the internal oscillator. Pin 4 — ON/OFF — Enable. When driven HIGH, this input pin enables the internal oscillator and EL driver outputs. Pin 5 — VSS — Power Supply Ground. Connect to the lowest circuit potential, typically ground. Pin 6 — COIL — Coil. The inductor for the boost converter is connected from VBATT to this pin. Pin 7 — CAP — Integrating Capacitor. An integrating capacitor connected from this pin to ground filters out any coil switching spikes or ripple present in the output waveform to the EL lamps. Connecting a fast recovery diode from COIL to CAP increases the light output of the EL lamp. Pin 8 — EL COMMON — Electroluminescent Lamp Common. This is a high voltage lamp driver output pin common to both EL lamps. Pin 9 — EL2 — Electroluminescent Lamp Output 2. This is a high voltage lamp driver output pin connect to the second EL lamp. Pin 10 — EL1 — Electroluminescent Lamp Output 1. This is a high voltage lamp driver output pin to connect to the first EL lamp. Rev. 9/12/00 SP4490 Two Panel Electroluminescent Lamp Driver © Copyright 2000 Sipex Corporation 3 6 COIL 7 CAP VDD 2 SP4490 SCR1 SCR2 SCR3 OSC fCOIL ROSC 3 fLAMP1 ON/OFF 4 FF7 VDD IN 0 fLAMPCOM fLAMP2 EL1/EL2 1 1 SEL 5 10 8 7 VSS EL1 ELcommon EL2 Figure 1: Internal Block Diagram of SP4490 DESCRIPTION The SP4490 electroluminescent lamp driver provides designers of cell phones, PDA's and other handheld, portable electronic devices with an integrated solution for driving two EL lamps independently. The SP4490 reduces system cost, component count and board space requirements over a discrete 2 EL driver approach. The EL lamp operates in opposite phase so the SP4490 can be easily implemented in applications driving multi-color or multi-segment EL lamps. The SP4490 operates from a +2.2V to +6.0V battery source. The device features a low power standby mode that draws less than 1mA. The frequency of the internal oscillator is set using a single external resistor. A single external inductor is required to generate the high voltage AC outputs to drive the EL lamps. All input pins are ESD protected with internal diodes to VDD and VSS. The SP4490 contains a DC-AC inverter that can produce an AC output of 180VPP (typical) from a 3.0V input voltage. An internal block diagram of the SP4490 can be found in Figure 1. Electroluminescent Technology An EL lamp consists of a thin layer of phosphorous material sandwiched between two strips of plastic which emits light (flouresces) when a high voltage AC signal is applied across it. It behaves primarily as a capacitive load. Long periods of DC voltage applied to the material tend to reduce its lifetime. With these conditions in mind, the ideal signal to drive an EL lamp is a high voltage sine wave. Traditional approaches to achieve this type of waveform include discrete circuits incorporating a transformer, transistors and several resistors and capacitors. This approach is large and bulky and cannot be implemented in most handheld equipment. Sipex offers low power single chip driver circuits specifically designed to drive small to medium sized electroluminescent panels. Sipex EL drivers provide a differential AC voltage without a DC offset to maximize EL lamp lifetime. The only additional components required for the EL driver circuitry are an inductor, resistor and capacitor. Rev. 9/12/00 SP4490 Two Panel Electroluminescent Lamp Driver © Copyright 2000 Sipex Corporation 4 VBATT EL1/EL2 ON/OFF 1 4 L1 470µH SP4490 VDD ROSC 464kΩ 2 6 COIL D1 1N4148 ROSC 3 7 5 CAP VSS C1 0.1µF C2* 10nF CINT 1800pF 10 EL1 8 ELcommon 9 EL2 * optional device EL Lamp EL Lamp Figure 2: Typical Application Circuit of SP4490 Electroluminescent backlighting is ideal when used with LCD displays, keypads or other backlit readouts. EL lamps uniformly light an area without creating any undesirable "hot spots" in the display. Also, an EL lamp typically consumes less power that LED's or incandescent bulbs in similar lighting situations. These features make EL ideal for attractive, battery powered products. THEORY OF OPERATION Coil Switch The SP4490 has an inductor-based boost converter to generate the high voltage used to drive the EL lamp. Energy is stored in the inductor according to the equation EL = 1/2 (LIpk2) where Ipk = (tON) (VBATT - VCEsat) /L. An internal oscillator controls the coil switch. During the time the coil switch is on, the coil is connected between VDD and the saturation voltage of the Rev. 9/12/00 coil switch is on, the coil is connected between VDD and coil switch and a magnetic field develops in the coil. When the coil switch turns off, the switch opens, the magnetic field collapses and the voltage across the coil rises. The internal diode forward biases when the coil voltage rises above the H-Bridge voltage and the energy enters the EL lamp. Each pulse increases the As the voltage approaches its maximum, the steps become smaller. (see figure 4). The brightness of the EL lamp output is directly related to energy recovery in the boost converter. There are many variations among coils such as magnetic core differences, winding differences and parasitic capacitances. For suggested coil suppliers refer to page 10. Oscillator The internal oscillator generates a high frequency clock used by the boost converter and H© Copyright 2000 Sipex Corporation SP4490 Two Panel Electroluminescent Lamp Driver 5 H-Bridge. An external resistor from VDD to ROSC sets the oscillator frequency. Typically a 464kΩ resistor sets the frequency to 44.0kHz. The high frequency clock directly controls the coil switch. This high frequency clock is divided by 128 to generate a low frequency clock which controls the EL H-Bridge and sets the EL lamp frequency. The oscillator has low sensitivity to temperature and supply voltage variations, increasing the performance of the EL driver over the operating parameters. Dual H-Bridge The H-Bridge consists of two SCR structures and two NPN transistors that control how the lamp is charged. Setting ON/OFF to HIGH activates the H-Bridge that is selected by EL1/ EL2. If the EL1/EL2 is low, EL1 is illuminated. If EL1/EL2 is HIGH, EL2 is illuminated. The EL driver illuminates the lamp by applying the high voltage supply of the boost converter to the lamp terminals through the H-Bridge and then switching the terminal polarity between the high voltage supply and ground at a constant frequency. This applies an AC voltage to the lamp that is twice the peak output voltage of the boost driver. An AC voltage greater than the 40V across the terminals of the lamp is typically necessary to adequately illuminate the EL lamp. Setting ON/OFF to LOW disables the outputs and places the circuit in a low power state. DESIGN CONSIDERATIONS Inductor Selection If limiting peak current draw from the power supply is important, small coil values (