SP4480NEB

SP4480 Dual Electroluminscent Lamp Driver s Backlights Keypad & LCD With A Single El Driver s A Single External IC Drives Dual EL Lamps Simultaneously Or Independently s A Single Coil Drives Both EL Lamp s A Single Resistor Controls the Operating Frequency s DC-to-AC Inverter Produces Up To 200VP-P s Low Current Standby Mode Draws Less Than 1µA s +2.2V to +6.0V Battery Operation DESCRIPTION The SP4480 provides a designer with two electroluminescent lamp drivers for backlighting solutions. The EL lamp outputs operate in opposite phase so he SP4480 device can be easily implemented into applications driving two EL lamps simultaneously or driving double-sided, multi-color EL lamps. The integration of a dual EL lamp driver in a cost-effective single IC reduces component count and board space requirements. The SP4480 is ideal for portable applications such as cellular phones, pagers, PDAs, medical equipment, and other designs with liquid crystal displays, keypads, and backlit readouts. The SP4480 operates from a +2.2V to +6.0V source. The device features a low power standby mode which draws less than 1µA (maximum). The frequency of the internal oscillator is set with a single external resistor. A single 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. ELEN1 1 ELEN2 2 ROSC 3 no connect 4 no connect 5 no connect 6 VSS 7 SP4480 14 VDD 13 EL2 12 EL1 11 EL3 10 EL4 9 8 CAP COIL SP4480DS/06 SP4480 Dual 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 14-pin SOIC (derate 8.33mW/˚C above +70˚C)....................700mW 14-pin TSSOP (derate 9.96mW/˚C above +70˚C)....................800mW 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 of 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 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 = 402kΩ, and TAMB = 25˚C unless otherwise noted. PARAMETER Supply Voltage, VDD Supply Current, IDD Shutdown Current, ISD = ICOIL + IDD ELEN Input Voltage, VELEN LOW HIGH Input Resistance ELEN1 and ELEN2 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 2 MAX. 6.0 4 1 UNITS V mA µA LCOIL = 470µH VELEN = 0V CONDITIONS 2.75 0 3.0 1 0.25 V 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 SP4480DS/06 SP4480 Dual Electroluminescent Lamp Driver 2 PINOUT ELEN1 1 ELEN2 2 ROSC 3 no connect 4 no connect 5 no connect 6 VSS 7 SP4480 14 VDD 13 EL2 12 EL1 11 EL3 10 EL4 9 8 CAP COIL PIN ASSIGNMENTS Pin 1 — ELEN1 — Electroluminescent Lamp Enable 1. When driven HIGH, this input pin enables the EL driver outputs for EL1 and EL2. This pin has an internal pulldown resistor. Pin 2 — ELEN2 — Electroluminescent Lamp Enable 2. When driven HIGH, this input pin enables the EL driver outputs for EL3 and EL4. This pin has an internal pulldown resistor. Pin 3 — ROSC — Oscillator Resistor. Connecting a resistor between VDD and this pin sets the frequency of the internal clock. Pin 4 — No Connect. Pin 5 — No connect. Pin 6 — No connect. Pin 7 — VSS — Power Supply Ground. Connect to the lowest circuit potential, typically ground. Pin 8 — COIL — Coil. The inductor for the boost converter is connected from VBATT to this pin. Pin 9 — 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 10 — EL4 — Electroluminescent Lamp Output 4. This is a high voltage lamp driver output pin paired with EL3 to drive the EL2 lamp. Pin 11 — EL3 — Electroluminescent Lamp Output 3. This is a high voltage lamp driver output pin paired with EL4 to drive the EL2 lamp. Pin 12 — EL1 — Electroluminescent Lamp Output 1. This is a high voltage lamp driver output pin paired with EL2 to drive the EL1 lamp. Pin 13 — EL2 — Electroluminescent Lamp Output 2. This is a high voltage lamp driver output pin paired with EL1 to drive the EL1 lamp. Pin 14 — VDD — Positive Power Supply. This pin should be bypassed with a 0.1µF capacitor. © Copyright 2000 Sipex Corporation SP4480DS/06 SP4480 Dual Electroluminescent Lamp Driver 3 8 COIL 9 CAP VDD 14 SP4480 OSC fCOIL 1.8kΩ SCR1 ROSC 3 SCR2 SCR3 SCR4 fLAMP1 ELEN1 1 fLAMP1 FF7 fLAMP2 ELEN2 2 7 fLAMP2 12 13 11 10 VSS EL1 EL2 EL3 EL4 Figure 1: Internal Block Diagram of SP4480 DESCRIPTION The SP4480 Dual Electroluminescent Lamp Driver is a low-cost, low voltage device ideal for the replacement of LED backlighting designs in keypads, handsets, PDAs and other portable designs. The EL lamp driver outputs operate in opposite phase so the SP4480 device can be easily implemented into applications driving two EL lamps simultaneously or double-sided EL lamps. Having a dual lamp driver solution on a single IC makes available precious printed circuit board real estate for designers additional circuitry. The SP4480 contains a DC-AC inverter that can produce an AC output of 180VP-P (typical) from a +2.2V to +6.0V input voltage. An internal block diagram of SP4480 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 SP4480DS/06 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. Electroluminescent backlighting is ideal when used with LCD's keypads or other backlit displays. EL lamps uniformly light an area without creating any undesirable "hot spots" in the display. Also, an EL lamp consumes less power that LED's or incandescent bulbs in similar © Copyright 2000 Sipex Corporation SP4480 Dual Electroluminescent Lamp Driver 4 VBATT ELEN1 ELEN2 1 2 L1 470µH SP4480 VDD ROSC 402kΩ 14 8 COIL D1 1N4148 ROSC 3 9 7 CAP VSS C1 0.1µF 1nF 12 13 EL1 * optional device EL2 11 10 EL3 EL4 CINT 1800pF EL Lamp EL Lamp Figure 2: Typical Application Circuit of the SP4480 lighting situations. These features make EL ideal for attractive, battery powered products. THEORY OF OPERATION Coil Switch The SP4480 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 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 voltage across the lamp in discrete steps. SP4480DS/06 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 HBridge. An external resistor from VDD to ROSC sets the oscillator frequency. Typically a 402kΩ resistor sets the frequency to 57kHz. 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 © Copyright 2000 Sipex Corporation SP4480 Dual Electroluminescent Lamp Driver 5 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 ELEN1 to HIGH activates the EL1 and EL2 outputs. Setting ELEN2 to HIGH activates EL3 and EL4 outputs. The EL driver illuminates the lamp by applying the high voltage supply of the boost converter to the lamp terminals through the HBridge and then switching the terminals 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. Both EL drivers may be operated simultaneously but with decreased light output from the EL panels. DESIGN CONSIDERATIONS Inductor Selection If limiting peak current draw from the power supply is important, small coil values (