XC9116 Series
Step-Up DC/DC Converter-Backlight LED Driver
ETR0407-002
GENERAL DESCRIPTION
The XC9116 series is a fixed frequency, constant current step-up DC/DC converter ideal for driving LEDs used in backlighting applications such as cellular phones, PDAs and digital cameras. Output voltage of up to 17.5V can be derived, therefore, four white LEDs in series can be driven. Since an LED current can be set by an external resistor when LEDs are in-series connection, all white LEDs can be turned on equably. A network of two parallel legs with three in each LED can be also driven. Luminance of the LEDs is controlled by changing the duty cycle of a PWM signal applied to the CE pin. Efficiency is high with the low feedback reference voltage ensuring the RLED losses are minimal. In addition, an internal MOSFET with an RDSON of 2.0 is used. A low profile and small board area solution can be achieved using a chip coil and an ultra small ceramic output capacitor (CL) of 0.22 F as a result of the high 1.0MHz switching frequency. The 'B' type of XC9116 has an additional fault detection circuit. If the LEDs are disconnected or damaged, excess or run away output voltage is prevented by stopping the drive of the internal MOSFET.
APPLICATIONS
For White LED drivers Mobile phones, PHS PDAs Digital still cameras
FEATURES
: 2.5V ~ 6.0V : Up to 17.5V externally set-up : Reference voltage 0.2V +5% Oscillation Frequency : 1.0MHz, 20% ON Resistance : 2.0 Efficiency : 86% (XC9116B Type) : 84% (XC9116D Type) (VIN=3.6V, ILED=20mA when driving 3 white LEDs in series) Control : PWM control Standby current : ISTB=1.0 A (MAX.) Load Capacitor : 0.22 F, ceramic Lx Limit Current : 325mA Lx Overvoltage Limit : XC9116B series No Lx Overvoltage Limit : XC9116D series Package : SOT-25 (SOT-23-5), USP-6B Input Voltage Range Output Voltage Range
TYPICAL APPLICATION CIRCUIT
SD XB0ASB03A1B VIN 2.5V~6.0V L:22uH VLF3010A VIN Lx
TYPICAL PERFORMANCE CHARACTERISTICS
XC9116B Type
CIN 1uF
CL 0.22uF
CE
100Hz to 10kHz
FB VSS RLED 10ohm 20mA
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XC9116 Series
PIN CONFIGURATION
6 5 4
1 2 3
SOT-25 (TOP VIEW)
*The dissipation pad of the USP-6B package should be left open. If the circuit needs to be connected to other pin, it should be connected to the VSS pin.
USP-6B (BOTTOM VIEW)
PIN ASSIGNMENT
PIN NUMBER SOT-25 USP-6B 1 2 3 4 5 2 3 1 6 4 5 PIN NAME Lx VSS FB CE VIN NC FUNCTION Switch Ground Voltage Feedback Chip Enable Power Input No Connection
CE PIN FUNCTION
CE PIN H L OPERATIONAL STATE Operation Shut-down
PRODUCT CLASSIFICATION
Ordering Information
XC9116123456 DESIGNATOR DESCRIPTION Lx Overvoltage Limit FB Voltage Oscillation Frequency Package Device Orientation SYMBOL B D 02 A M D R L : Available : Not available : 0.2V : 1MHz : SOT-25 : USP-6B : Embossed tape, standard feed : Embossed tape, reverse feed DESCRIPTION
1 23 4 5 6
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XC9116
Series
BLOCK DIAGRAMS
XC9116B02A
Current Sense & Limit Error Amp + Current Feedback + PWM Comparater VSS Buffer Driver MAX Duty Limit Lx Over Voltage Limit Lx
VIN FB
Phase 0.2V Compensation CE CE
Ramp Wave Generator, OSC
XC9116D02A
V IN Error Amp FB + 0.2V CE Current Feedback Phase Compensation CE + PWM Comparater
Current Sense & Limit LX
Buf f er Driver
Ramp Wave Generator, OSC
VSS
ABSOLUTE MAXIMUM RATINGS
PARAMETER VIN Pin Voltage Lx Pin Voltage FB Pin Voltage CE Pin Voltage Lx Pin Current Power Dissipation SOT-25 USP-6B SYMBOL VIN VLx VOUT VCE ILx Pd Topr Tstg RATINGS VSS - 0.3 ~ 7.0 VSS - 0.3 ~ 22.0 VSS - 0.3 ~ 7.0 VSS - 0.3 ~ 7.0 1000 250 100 - 40 ~ + 85 - 55 ~ +125
Ta = 25OC UNITS V V V V mA mW
O O
Operating Temperature Range Storage Temperature Range
C C
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XC9116 Series
ELECTRICAL CHARACTERISTICS
XC9116B02AMR PARAMETER FB Control Voltage Output Voltage Range Input Voltage Range Supply Current 1 Supply Current 2 Standby Current Oscillation Frequency Maximum Duty Cycle (*1) Efficiency (*2) Current Limit Lx Overvoltage Limit Lx ON Resistance Lx Leak Current CE "High" Voltage CE "Low" Voltage CE "High" Current CE "Low" Current FB "High" Current FB "Low" Current Ta = 25 OC SYMBOL VFB VOUTSET VIN IDD1 IDD2 ISTB FOSC MAXDTY EFFI ILIM VLxOVL RSWON ILxL VCEH VCEL ICEH ICEL IFBH IFBL CONDITIONS FB MIN. 0.19 VIN 2.5 0.8 86 225 18.0 0.65 -0.1 -0.1 -0.1 -0.1 TYP. 0.20 450 60 0 1.0 92 86 325 19.0 2.0 0 MAX. 0.21 17.5 6.0 750 140 1.0 1.2 98 425 22.0 1.0 0.2 0.1 0.1 0.1 0.1 UNIT. V V V A A A MHz % % mA V A V V A A A A
CIRCUIT
VIN=Lx, FB=0.4V CE=0V, Lx=5.0V
1 1 1 2 3 3 2 2 1 4 2 2 3 2 2 3 3 3 3
When connected to ext. components, VIN=3.6V, RLED=20 When connected to ext. components, VIN=3.6V Voltage which Lx pin voltage holding "H" level VIN > 2.5V VIN=3.6V, VLx=0.4V Same as ISTB CE applied voltage when Lx starts oscillation CE applied voltage which Lx pin voltage holding "H" level Same as IDD2 Same as ISTB Same as IDD2 Same as ISTB
Unless otherwise stated, VIN=3.0V, CE=3.0V, FB=0V, Vpull=5.0V NOTE: *1: The duty ratio is forcibly reduced when maximum duty cycle periods are repeated. *2 : LED : NSPW310BS x 3, EFFI = {[(output voltage) x (output current)] / [(input voltage) x (input current)]} x 100
XC9116D02AMR PARAMETER FB Control Voltage Output Voltage Range Lx Operating Voltage Range Operating Voltage Range Supply Current 1 Supply Current 2 Standby Current Oscillation Frequency Maximum Duty Cycle Efficiency (*1) Current Limit Lx ON Resistance Lx Leak Current CE "High" Voltage CE "Low" Voltage CE "High" Current CE "Low" Current FB "High" Current FB "Low" Current
SYMBOL VFB VOUTSET VLx VIN IDD1 IDD2 ISTB FOSC MAXDTY EFFI ILIM RSWON ILxL VCEH VCEL ICEH ICEL IFBH IFBL
CONDITIONS FB
MIN. 0.19 VIN 2.5 0.8 86 225 0.65 -0.1 -0.1 -0.1 -0.1
TYP. 0.20 450 50 0 1.0 92 84 325 2.0 0 -
MAX. 0.21 19.5 20.0 6.0 750 120 1.0 1.2 98 425 3.6 1.0 0.2 0.1 0.1 0.1 0.1
Ta = 25 OC UNIT CIRCUIT V 1 V 1 V V A A A MHz % % mA A V V A A A A 1 1 2 3 3 2 2 1 4 2 3 2 2 3 3 3 3
VIN=Lx, VFB=0.4V VCE=0V, VLx=5V
When connected to ext. components, VIN=3.6V, RLED=20 When connected to ext. components, VIN=3.6V VIN=3.6V, VLx=0.4V, Rpull=10 Same as ISTB CE applied voltage when Lx starts oscillation CE applied voltage which Lx pin voltage holding "H" level Same as IDD2 Same as ISTB Same as IDD2 Same as ISTB
Test conditions: Unless otherwise stated, VIN=3.0V, VCE=3.0V, VFB=0V, Vpull=5.0V, Rpull=100 Notes: *1: LED: NSPW310BS x 3, EFFI = {[(output voltage) x (output current)] / [(input voltage) x (input current)]} x 100
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XC9116
Series
TYPICAL APPLICATION CIRCUITS
XC9116B02A XC9116D02A
EXTERNAL COMPONENTS
SYMBOL L SBD (*1) CIN CL (*3) ZD (*4) R1
NOTE :
VALUE 22 H 4.7 F 0.22 F 18V 100
PART NUMBER VLF3010A-220MR XB0ASB03A1BR (*2) MA2Z720 JMK107BJ475MA-B TMK107BJ224KA-B MAZ8180 -
MANUFACTURER TDK TOREX PANASONIC TAIYO YUDEN TAIYO YUDEN PANASONIC -
*1: Please use a Schottky barrier diode (SBD) with a low junction capacitance, Cj.
*2: For using the XB0ASB03A1BR with four white LEDs in series, please be noted with a direct reverse voltage (VR=20V) and a repetitive peak reverse voltage (VRM=30V). *3: Use ceramic capacitors processing a low temperature coefficient. *4: Please refer to the LED Open-circuit Protection at Application Information for setting the Zener diode.
OPERATIONAL EXPLANATION
The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase compensation circuit, Lx overvoltage limit circuit, N-channel MOS driver transistor, current limiter circuit and others. The series ICs compare, using the error amplifier, the voltage of the internal voltage reference source with the feedback voltage from the FB pin. Phase compensation is performed on the resulting error amplifier output, to input a signal to the PWM comparator to determine the turn-on time during switching. The PWM comparator compares, in terms of voltage level, the signal from the error amplifier with the ramp wave from the ramp wave circuit, and delivers the resulting output to the N-channel MOS driver transistor to cause the Lx pin to output a switching duty cycle. This process is continuously performed to ensure stable output voltage. The current feedback circuit detects the N-channel MOS driver transistor's current for each switching operation, and modulates the error amplifier output signal. This enables a stable feedback loop even when a low ESR capacitor, such as a ceramic capacitor, is used, ensuring stable output voltage. The reference voltage source provides the reference voltage to ensure stable output voltage of the IC. The ramp wave circuit determines switching frequency. The 1MHz (TYP.) of frequency is fixed internally. Clock pulses generated in this circuit are used to produce ramp waveforms needed for PWM operation. The error amplifier is designed to monitor output voltage. The amplifier compares the reference voltage with the FB pin voltage. When a voltage lower than the reference voltage is fed back, the output voltage of the error amplifier increases. Gain and frequency characteristics of the error amplifier output are fixed internally as an optimize signal.
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XC9116 Series
OPERATIONAL EXPLANATIONS (Continued)
The current limit circuit of the XC9116 series monitors the current flowing through the N-channel MOS driver transistor connected to the Lx pin, and features a combination of the constant-current type current limit mode and the duty cycle limit of the next pulse. 1When the driver current is greater than a specific level, the constant-current type current limit function operates to turn off the pulses from the Lx pin at any given timing. 2The IC controls the next pulse to be smaller than the first pulse.
Current Limit Current Limit
IL
LX
The current w ill be of f w hen the coil current reaches the value of the constant current limit. Limit some duty pulses af ter the limit.
XC9116B series' Lx overvoltage limit circuit monitors the Lx pin voltage. When the Lx pin voltage exceeds than 19V (TYP.), the IC performs the function of latching the OFF state of the driver transistor, and goes into operation suspension mode. In suspension mode, operations can be resumed by restoring power to the VIN pin. The suspension mode does not mean a complete shutdown, but a state in which pulse output is suspended; therefore, the internal circuitry remains in operation. The XC9116B series' maximum duty cycle limit circuit monitors the duty cycle. When the maximum duty cycle is repeated for a certain time, the IC controls the error amplifier output so that the duty cycle of the next pulse becomes smaller than that of the first pulse. The operation of the XC9116 series will enter into the shut down mode when a low level signal is input to the CE pin. During the shut down mode, the supply current is 0 A (TYP.), with high impedance at the Lx pin. The IC starts its operation with a high level signal to the CE pin. The input to the CE/MODE pin is a CMOS input and the sink current is 0 A (TYP.). 100 s after disable, the IC goes into suspension mode and supply current is minimal. After this, the IC will be in stand-by mode and the supply current will be 0 A (TYP.).
NOTES ON USE
Please connect the anode of a Schottky barrier diode and an inductor to the Lx pin. The reference voltage is 200mV (TYP.). A resistor (RLED) should be connected to the FB pin for setting the cathode of LEDs and a constant current value. The resistance value can be calculated by the following equation. RLED=0.2 / ILED ILED=Setting constant current value Typical example: ILED 5mA 10mA RLED 40 20 ILED 13.3mA 20mA RLED 15 10
An ENABLED state is reached when the CE voltage exceeds 0.65V and a DISABLED state when the CE Voltage falls below 0.2V. Please connect an inductor and an input by-pass capacitor (CIN) to the VIN pin.
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XC9116
Series
APPLICATION INFORMATION
1. Applying PWM signal to the CE pin The XC9116 repeats on/off operations by a PWM signal applied to the CE pin. The magnitude of LED current, ILED, when the diode is on, is determined by RLED. The magnitude is zero when the diode is off. The average of LED current is proportional to the positive duty ratio of the PWM signal. The frequency of the PWM signal can be controlled to the optimum value between 100Hz and 10kHz. With regard to the amplitude of the PWM signal, the high level should be higher than the "H" voltage of CE, VCEH, and the low level, lower than the "L" voltage of CE, VCEL.
20
s / div
20
s / div
4 series
200
s / div
200
s / div
2. Step-Wise Regulation of LED Current In some applications, it may be necessary to incorporate step-wise regulation of LED current, ILED. Step-wise regulation of LED illumination is achieved by connecting a switch element SW1 in parallel with RLED and in series with RLED1 and turning SW1 on and off, as shown below. Choose a resistance of RLED so that the minimum necessary current is gained when switch element SW1 is off. The resistance of RLED1 should be such that a desired increase of current passed through the LED is gained when the switch element is on.
L VIN SD
Ex.) Current ILED = 5mA and 15mA RLED = 200mV / 5mA = 40 RLED1 = 200mV / (15mA - 5mA) = 20
ILED VIN CIN CE ON/OFF VSS RLED signal SW1 FB RLED1 Lx CL
Figure : Circuit using Step-wise Regulation of LED Current
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XC9116 Series
APPLICATION INFORMATION (Continued)
3. Using DC Voltage If in an application it is necessary to control the LED current by a variable DC voltage, illumination control of LED is achieved by connecting R1 and R2 and applying a direct-current voltage to R2, as shown below. When R1>>RLED, ILED which flows into LEDs can be calculated by the following equation;
ILED = (VREF - R1 / R2 (VDC - VREF)) / RLED VREF = 0.2V (TYP.) Ex.1) When R1 = 10k , R2 = 100k , RLED = 10 , In the range of 0.2V to 2.2V DC, ILED (LED current) varies between 20mA to 0mA.
ZD XC9116 FB VDC R2
ILED
(
)
R1 RLED
Figure : Circuit using DC voltage Ex.2) When R1 = 10k , R2 = 100k , R3 = 10k , C1 = 0.1F, RLED = 10, the average LED current will be 10mA by inputting a PWM signal of CE `H' level: 2.2V, CE 'L' level: 0V, duty cycle: 50%, oscillation frequency: 100Hz. As well as the way of dimming control by applying the PWM signal to the CE pin, the average LED current increases proportionally with the positive duty cycle of the PWM signal.
ZD XC9116 FB PWM R3 C1 R2
ILED
(
)
R1 RLED
Figure : Circuit inputting a PWM signal to the FB pin When the input voltage (VIN) is high, minimum illumination may occur even if the CE pin is in the disable state. If this happens, please connect a transistor to between the LED and the FB pin. By driving the CE signal in-phase and cutting the pass to current, the minimum illumination can be prevented.
L:22uH VLF3010A VIN 3.6V (3.2V~6.0V) SD XB0ASB03A1B
VIN CIN 4.7uF CE GND
Lx XP151A21A2 FB RLED 10 20mA
CL 0.22uF (base)
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XC9116
Series
APPLICATION INFORMATION (Continued)
It is possible to illuminate three-series two parallel white LEDs, six in total, using an input voltage VIN 3.2V.
L:22uF CDRH3D16 VIN 3.2V~6.0V SD XB0ASB03A1B
CIN: 4.7uF
VIN
Lx CL: 0.22uF
CE VSS
FB RLED1 10 RLED1 10
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