EUP2796 EUTECH | Alldatasheet

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DS2796 Ver1.0 Feb. 2007 Dual-Display White LED Driver with 3/2X Switched Capacitor Boost

DESCRIPTION

The EUP2796 is a charge-pump based white-LED driver that is ideal for mobile phone display backlighting. It can drive up to 6 LEDs in parallel with up to 20mA through each LED. Regulated internal current sources deliver excellent current and brightness matching in all LEDs. The LED-driver current sources are split into two independently controlled groups. The primary group (4 LEDs) can be used to backlight the main phone display. The second group (2 LEDs) can be used to backlight a secondary display or to provide other lighting features (keypad LEDs, for example). Brightness of the two groups can be adjusted independently with pulse-width modulated (PWM ) digital signals. The EUP2796 works off an extended Li-Ion input voltage range (2.7V to 5.5V). Voltage boost is achieved with a high-efficiency 3/2- gain charge pump. The EUP2796 is available in a 16-pin TQFN package. Typical Application Circuit

FEATURES

z Drives up to 6 LEDs with up to 20mA each z LEDs controlled in 2 Distinct Groups, for Backlighting 2 Displays (main LCD and sub-LCD) z Excellent Current and Brightness Matching z High Efficiency 3/2X Charge Pump z Extended Li-Ion Input: 2.7V to 5.5V z PWM Brightness Control: 100Hz - 1kHz z 3mm×3mm TQFN-16 Package z RoHS Compliant and 100% Lead(Pb)-Free

APPLICATIONS

z Mobile Phone Display Lighting z Mobile Phone Keypad Lighting z PDAs z General LED Lighting Figure 1.

DS2796 Ver1.0 Feb. 2007 Pin Configurations Package Type Pin Configurations TQFN-16 Pin Description PIN Pin DESCRIPTION C2P 1 Positive terminal of C2 POUT 2 Charge pump output ISET 3 Current sense input. Connect 1% resistor to ground to set constant current through LED ENS 4 Enable for Group-B LEDs (D5~D6). Logic input High=Group-B LEDs ON. Low=GroupB LEDs OFF. Pulsing this pin with a PWM signal (100Hz-1kHz) can be used to dim LEDs. ENM 5 Enable for Group-A LEDs (D1~D4). Logic input High=Group-A LEDs ON. Low=GroupA LEDs OFF. Pulsing this pin with a PWM signal (100Hz-1kHz) can be used to dim LEDs. LED1-6 11,10,9,8,7,6 Current source outputs. Connect directly to LED GND 12 Power supply ground input C1N 13 Negative terminal of C1 VIN 14 Power supply voltage input C2N 15 Negative terminal of C2 C1P 16 Positive terminal of C1

DS2796 Ver1.0 Feb. 2007

Ordering Information

Order Number Package Type Marking Operating Temperature range EUP2796JIR1 TQFN-16 xxxx 2796A -40 °C to 85°C EUP2796- □ □ □ □ L e a d F r e e C o d e 1: Lead Free 0: Lead Packing R : T a p e & R e e l Operating temperature range I: Industry Standard Package Type J : T Q F N - 1 6 Block Diagram Figure 2.

DS2796 Ver1.0 Feb. 2007 Absolute Maximum Ratings „ ESD Rating Operating Conditions

Electrical Characteristics

Limits in standard typeface and typical values apply for TJ = 25°C. Limits in boldface type apply over the full operating junction temperature range (-40˚C ≤ TJ≤ 85˚C) . Unless otherwise specified: VIN=3.6V; VDX = 3.4V; V(EN) = 2.0V; Group A and Group B LEDs not ON simultaneously (ENM = ENS=VIN ); RSET = 7.5kΩ; CIN, C1,C2, and CPOUT = 1µF. EUP2796 Symbol Parameter Conditions Min Typ Max. Unit 3.0V ≤ VIN ≤ 4.2V , and VIN = 5.5V 2.5V ≤ VDX ≤ 3.4V ;RSET=7.5kΩ 14.3 (-8%) 15.5 16.8 (+8%) mA(%) 3.0V ≤ VIN ≤ 5.5V , 2.5V ≤ VDX ≤ 3.4V ;RSET=11.8kΩ 10 3.0V ≤ VIN ≤ 5.5V , 2.5V ≤ VDX ≤ 3.4V ;RSET=7.5kΩ 15 IDX Output Current Regulation 2.7V ≤ VIN ≤ 3.0V , 2.5V ≤ VDX ≤ 3.4V ;RSET=5.8kΩ 20 mA ID-MATCH Current Matching Between Any Two Group A Outputs or Group B Outputs VIN =3.0V ±0.3 % IQ Quiescent Supply Current 2.7V ≤ VIN ≤ 4.2V , No Load Current, ENM=ENS=OFF 4 7.5 mA ISD Shutdown Supply Current 2.7V ≤ VIN ≤ 5.5V , EN=OFF 0.1 1 µA VSET I SET Pin V oltage 2.7V ≤ VIN ≤ 5.5V 1.18 V IDX / ISET Output Current to Current Set Ratio 100 ROUT Charge Pump Output Resistance V IN =3.0V 3.5 Ω IDX=95% × I DX (nom) RSET=7.5kΩ (IDX (nom) ≈15mA) 300 VHR Current Source Headroom V oltage Requirement IDX=95% × I DX (nom) RSET=11.8kΩ (IDX (nom) ≈10mA) 200 mV fSW Switching Frequency 3.0V ≤ VIN ≤ 4.2V 500 kHz tSTART Start-up Time I DX=90% ISET VIL SD Input Logic Low 2.7V ≤ VIN ≤ 5.5V 0.5 V VIH SD Input Logic High 2.7V ≤ VIN ≤ 5.5V 1.1 V ILEAK Input Leakage Current V ENX= 0V 0.1 µA

DS2796 Ver1.0 Feb. 2007 LED Current vs VIN 14.50 14.75 15.00 15.25 15.50 15.75 16.00 16.25 Power Supply (V) LED Current (mA) TA=25℃ LED Current vs RSET 0.00 5.00 10.00 15.00 20.00 25.00 30.00 0 2 04 06 08 0 1 0 0 R SE T R esistance (kΩ) LED Current (mA) Efficient vs Supply Voltage Driving Six WLEDs (Rset=7.5KΩ, VLED=3.6V) 100 Supply Voltage(V) Efficiency (%) Typical Operating Characteristics Vset vs Power Supply 1.16 1.17 1.18 1.19 1.20 Pow er Supply (V) Vset Voltage Head Room Voltage vs LED Current 0.00 5.00 10.00 15.00 20.00 Head Room Voltage LED Current (mA) Input Current vs. Supply Voltage Driving Six WLEDs (Rset=7.5KΩ, VLED=3.6V） 100 110 120 130 140 150 160 Supply Voltage(V) Input Current (mA)

DS2796 Ver1.0 Feb. 2007 Input Current vs. Supply Voltage (Rset=7.5KΩ, VLED=3.6V） 100 120 140 160 Supply Voltage(V) Input Current (mA)

6 LEDs

4 LEDs

2 LEDs

LED Current Matching vs. Supply Voltage (Rset=7.5KΩ,VLED=3.6V) 14.50 14.75 15.00 15.25 15.50 15.75 16.00 16.25 Supply Voltage(V) LED Current (mA)

DS2796 Ver1.0 Feb. 2007

Application Information

Enable Pins: ENM, ENS The EUP2796 has 2 enable pins-ENM and ENS, which control the main and sub LEDs. All two are active-high logic (HIGH = ON). When both of ENM or ENS voltage is low (<0.5V), the part is in shutdown mode. All internal circuitry is OFF and the part consumes almost no supply current when the EUP2796 is shutdown. When the voltage on either of ENM and ENS pin is high (>1.1V), the part is active. The charge pump is ON, and turn on the output currents to drive the LEDs. ENM activates /deactivates the four group-A outputs (D1-D4). ENS activates/deactivates the two group-B outputs (D5-D6). There is no pull down resistors that are connected internally between each of the enable pins to ground. Setting LED Currents The output currents of the EUP2796 can be set to a desired value simply by connecting an appropriately sized resistor (R SET) between the I SET pin of the EUP2796 and GND. The ou tput currents (LED currents) are proportional to the current that flows out of the I SET pin. The output currents are a factor of 100 greater than the I SET current. The feedback loop of an internal amplifier sets the voltage of the I SET pin to 1.18V(typ.). Placing a resistor between I SET and GND programs the ISET current, and thus the LED currents. The statements above are si mplified in the equations below: () SETSETDXX RV001I ××= () DXXSET IV18.1001R ××= Maximum Output Current, Maximum LED Voltage, Minimum Input Voltage The EUP2796 can drive 6 LEDs at 15mA each from an input voltage as low as 3.0V , so long as the LEDs have a forward voltage of 3.6V or less (room temperature). The statement above is a simple example of the LED drive capabilities of the EUP2796. The statement contains the key application parameters that are required to validate an LED- drive design using the EUP2796: LED current (I LED), number of active LEDs (N), LED forward voltage (V LED), and mini- mum input voltage (VIN-MIN). The equation below can be used to estimate the total output current capability of the EUP2796: () 1.eq,KRN VV5.1I HROUT LEDINMAX_LED +∗ −∗= mA/mV124N VV5.1I LEDINMAX_LED +Ω∗ −∗= ROUT – Output resistance. This parameter models the internal losses of the charge pump that result in voltage droop at the pump output P OUT. Since the magnitude of the voltage droop is proportional to the total output current of the charge pump, the loss parameter is modeled as a resistance. The output resistance of the EUP2796 is typically 4Ω (V IN = 3.0V , TA = 25˚C). In equation form: () 2.eqRINV5.1V OUTLEDINPOUT ××−×= KHR – Headroom constant. This parameter models the minimum voltage required to be present across the current sources for them to regulate properly. This minimum voltage is proportional to the programmed LED current, so the constant has units of mV/mA. The typical K HR of the EUP2796 is 12mV/mA. In equation form: ( )( ) 3.eqIKVV LEDHRLEDPOUT ×>− The "I LED-MAX" equation (eq. 1) is obtained from combining the R OUT equation (eq. 2) with the K HR equation (eq. 3) and solving for I LED. Maximum LED current is highly dependent on minimum input voltage and LED forward voltage. Output current capability can be increased by raising the minimum input voltage of the application, or by selecting an LED with a lower forward voltage. Excessive power dissipation may also limit output current capability of an application.

DS2796 Ver1.0 Feb. 2007 Soft-Start The EUP2796 contains internal soft-start circuitry to limit input inrush currents when the part is enabled. Soft start is implemented internally with a controlled turn-on of the internal voltage reference. During soft start, the current through the LED outputs rise at the rate of the reference voltage ramp. Due to the soft-start circuitry, turn-on time of the EUP2796 is approximately 100µs (typ.). Thermal Protection Internal thermal protection circuitry disables the EUP2796 when the junction temperature exceeds 160˚C (typ.). This feature pr otects the device from being damaged by high die temperatures that might otherwise result from exce ssive power dissipation. The device will recover and operate normally when the junction temperature falls below 140 ˚C (typ.).It is important that the board layout provides good thermal conduction. This will help to keep the junction temperature within specified operating ratings. Adjusting LED Brightness (PWM control) Perceived LED brightness can be adjusted using a PWM control signal to tu rn the EUP2796 current sources ON and OFF at a rate faster than perceptible by the eye. When this is done, the total brightness perceived is proportional to the duty cycle (D) of the PWM signal (D = the percentage of time that the LED is on in every PWM cycle). A simple example: if the LEDs are driven at 15mA each with a PWM signal that has a 50% duty cycle, perceived LED brightness will be about half as bright as compared to when the LEDs are driven continuously with 15mA. A PWM signal thus provides brightness (dimming) control for the solution. The minimum recommended PWM frequency is 100Hz. Frequencies below this may be visibly noticeable as flicker or blinking. The maximum recommended PWM frequency is 1kHz. Frequencies above this may cause interference with internal current driver circuitry. The preferred method for applying a PWM signal to adjust brightness is to keep the master EN voltage ON continuously and to apply the PWM signal(s) to the current source enable pin(s): ENM and/or ENS. The benefit of this type of connection can be best understood with a contrary example. When a PWM signal is connected to the master enable (EN) pin, the charge pump repeatedly turns on and off. Every time the charge pump turns on, there is an inrush of current as capacitances, both internal and external, are recharged. This inrush current results in a current and voltage spike at the input of the part. By only applying the PWM signal to ENM/ENS, the charge pump stays on continuously and much lower input noise results. In cases where a PWM signal must be connected to the EN pin, measures can be taken to reduce the magnitude of the charge-pump turn-on voltage spikes. More input capacitance, series resistors and/or ferrite beads may provide benefits. Capacitor Selection The EUP2796 requires 4 ex ternal capacitors for proper operation. Surface- mount multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low equivalent series resistance (ESR<20m Ω typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are not recommended for use with the EUP2796 due to their high ESR, as compared to ceramic capacitors. For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with the EUP2796. These capacitors have tight capacitance tolerance (as good as ±10%) and hold their value over temperature (X7R: ±15% over -55 ˚C to 125˚C; X5R: ±15% over -55˚C to 85˚C). Capacitors with Y5V or Z5Utemperature characteristic are generally not recommended for use with the EUP2796. Capacitors with these temperature characteristics typically have wide capacitance tolerance (80%,-20%) and vary significantly over temperature (Y5V: 22%, -82% over -30˚C to 85 ˚C range; Z5U: 22%, -56% over 10 ˚C to 85˚C range). Under some conditions, a nominal 1µF Y5V or Z5U capacitor could have a capacitance of only 0.1µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum capacitance requirements of the EUP2796. For LED driver applications, the input voltage ripple is more important than output ripple. Input ripple is controlled by input capacitor CIN, increasing the value of input capacitance can further reduce the ripple. Practically, the input voltage ripple depends on the power supply’s impedance. If a single input capacitor CIN cannot satisfy the requirement of application, it is necessary to add a low-pass filter.

DS2796 Ver1.0 Feb. 2007 Packaging Information T Q F N - 1 6 MILLIMETERS INCHES SYMBOLS MIN. MAX. MIN. MAX. A 0.70 0.80 0.028 0.031 A1 0.00 0.05 0.000 0.002 b 0.18 0.30 0.007 0.012 E 2.90 3.10 0.114 0.122 D 2.90 3.10 0.114 0.122 D1 1.70 0.067 E1 1.70 0.067 e 0.50 0.020 L 0.30 0.50 0.012 0.020