SM8121A White LED Driver IC OVERVIEW The SM8121A is a high efficiency step-up DC-DC converter. Due to high voltage CMOS process realizing 25V output supply as maximum value, 2 to 6 lights of white LED connected in series can be lighted. By connecting in series, current variation among LED is eliminated. Current value sent to white LED can be set by external resistors. In addition, brightness can also be adjusted by control to FB pin or CE pin. FEATURES PINOUT ■ Boost-up control using PWM ■ 2 to 6 lights of white LED (connected in series) lighted ■ Output current value can be set by external resistors (51Ω: 9.8mA, 33Ω: 15.2mA, 24Ω: 20.8mA) ■ Brightness adjustable by control to FB pin or CE pin ■ Current variation among LED decreased by high precision ■ High efficient drive by step-up model ■ Supply voltage range: 2.3 to 5.5V ■ Maximum output voltage: 25V ■ Quiescent current: 400μA (typ) ■ Standby current: 1.0μA (max) ■ RON (Switching MOS-Tr): 2Ω(typ) ■ Switching frequency: 1.0MHz (typ) ■ Output current detection accuracy: ±2% ■ Small package: SOT23-5 (SM8121AH) (Top View) ■ SOT23-5 SW 1 VSS 2 FB 3 5 VDD 4 CE APPLICATIONS ■ Cellular phone ■ Pager ■ Digital still camera ■ Handy terminal ■ PDAs ■ Portable games ■ White LED drive ■ LCD bias supply ■ Flash memory supply ORDERING INFORMATION Device Package SM8121AH SOT23-5 SEIKO NPC CORPORATION - 1 SM8121A PACKAGE DIMENSIONS (Unit: mm) SOT23-5 + 0.2 1.6 − 0.1 + 0.2 2.8 − 0.3 0.20MIN ■ + 0.1 0.15 − 0.05 1.9 ± 0.2 2.9 ± 0.2 0.4 ± 0.1 0 ~ 0.10 0.8 ± 0.1 1.1 ± 0.1 0.12 M 0.95 0.1 0.5 2.0 ( 0.3 ) ( 0.3 ) 3.0 ± 0.1 2.6 ± 0.1 0.3TYP 1.6 ± 0.1 1.1 + 0.1 0.75 − 0.05 0.2 ± 0.1 0.2 ± 0.1 SON-6 0.125 ± 0.05 ■ 0.05 + 0.1 0.2 − 0.05 0.05 M SEIKO NPC CORPORATION —2 SM8121A BLOCK DIAGRAM SW VDD Buff PWM COMP FB ERR AMP VREF RAMP GENERATOR CE OSC SOFT START VSS PIN DESCRIPTION Number Name I/O Description 1 SW O Coil switching 2 VSS - GND 3 FB I Feed back (Output current detection) 4 CE IP*1 Chip enable (High active) 5 VDD - Power supply *1. Input with built-in pull-down resistor SEIKO NPC CORPORATION - 3 SM8121A SPECIFICATIONS Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage range VDD −0.3 to 6.5 V Input voltage range VIN VSS – 0.3 to VDD + 0.3 V SW output voltage range VSW –0.3 to 27 V SW input current ISW 500 mA Power dissipation PD 250 (Ta = 25°C) mW Operating temperature range Topr –40 to 85 °C Storage temperature range Tstg −55 to 125 °C Electrical Characteristics VDD = 3.6V, VSS = 0V, Ta = 25°C unless otherwise noted Rating Parameter Pin Symbol Condition Unit min typ max Supply voltage VDD VDD 2.3 3.6 5.5 V Maximum output voltage SW VOUT – – 25 V Standby current VDD ISTB VCE = 0V – – 1.0 µA 150 300 µA VDD IDD VFB = 1.0V – Quiescent current VFB = 0V – 400 800 µA SW-Tr ON resister SW RON ISW = 100mA, VDD = 3.6V – 2.0 3.0 Ω SW-Tr leak current SW ILEAK VSW = VDD – – 1.0 µA Switching frequency SW fOSC VFB = 0V 0.9 1.0 1.1 MHz Maximum duty SW Duty VFB = 0V 65 75 85 % – – V CE VIH 2.0 Input voltage VIL – – 0.6 V CE ICE VCE = 3.6V – 5.0 10 µA FB IFB VFB = 0.5V –1.0 – 1.0 µA Soft-start time SW TSS – 500 – µs FB voltage FB VFB 0.49 0.50 0.51 V Coil inductance SW LSW – – 10 µH Input current SEIKO NPC CORPORATION —4 SM8121A Typical Characteristics VSS = 0V, Ta = 25°C unless otherwise noted 1000 800 600 400 200 100 1000 90 900 Soft-start time (TSS) [µs] Maximum duty (Duty) [%] Switching frequency (fosc) [kHz] 1200 80 70 60 50 40 30 20 10 0 2.5 3.5 4.0 4.5 5.0 5.5 2.5 Supply voltage (VDD) [V] 7 6 5 4 3 2 1 4.0 4.5 5.0 4.5 5.0 1.0 0.5 3.0 3.5 4.0 4.5 5.0 3.5 4.0 4.5 5.0 600 500 400 300 200 100 2.5 VDD vs. IDD (VFB = 1.0V) 3.0 3.5 4.0 4.5 5.0 5.5 0.505 0.500 0.495 0.490 0.485 0.480 4 3 2 1 5.0 Supply voltage (VDD) [V] VDD vs. VFB 5.5 3.5 4.0 4.5 5.0 5.5 10 9 8 7 6 5 4 3 2 1 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 40 30 20 10 0 0 4.5 3.0 50 SW-Tr leak current (ILEAK) [pA] SW-Tr ON resister (RON) [Ω] 0.510 4.0 25 VDD vs. IFB (VFB = 0.5V) 5 0.515 3.5 50 Supply voltage (VDD) [V] VDD vs. IDD (VFB = 0V) 0.520 3.0 75 Supply voltage (VDD) [V] Supply voltage (VDD) [V] 2.5 100 VDD vs. ISTB (VCE = 0V) 700 5.5 5.5 Supply voltage (VDD) [V] 0 0 5.0 125 2.5 FB pin input current (IFB) [pA] Quiescent current (IDD) [µA] 100 4.5 150 5.5 800 200 4.0 0 2.5 VDD vs. VTH 300 3.5 175 Supply voltage (VDD) [V] 400 3.0 VDD vs. TSS 1.5 5.5 500 3.0 200 Supply voltage (VDD) [V] 2.0 VDD vs. ICE (VCE = VDD) 2.5 300 0 2.5 5.5 0.0 4.0 400 200 Supply voltage (VDD) [V] Quiescent current (IDD) [µA] 3.5 Standby current (ISTB) [pA] CE pin input voltage (VTH) [V] CE pin input current (ICE) [µA] 8 0 FB voltage (VFB) [V] 3.0 2.5 9 3.5 500 VDD vs. Duty 10 3.0 600 Supply voltage (VDD) [V] VDD vs. fOSC 2.5 700 100 0 3.0 800 2.5 3.0 3.5 4.0 4.5 5.0 Supply voltage (VDD) [V] VDD vs. RON 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Supply voltage (VDD) [V] VDD vs. ILEAK SEIKO NPC CORPORATION —5 SM8121A 100 1000 900 1000 90 80 800 600 400 200 70 60 50 40 30 20 0 25 50 75 0 −50 −25 100 Topr vs. fOSC 25 50 75 7 6 5 4 3 2 1 50 75 1.0 0.5 0 25 50 75 100 50 75 600 500 400 300 200 100 −50 −25 Topr vs. IDD (VFB = 1.0V) 0 25 50 75 100 0.520 0.490 0.485 0.480 −50 −25 4 3 2 1 0 0 25 50 75 100 Operating temperature (Topr) [°C] Topr vs. VFB 50 75 100 500 450 400 350 300 250 200 150 100 50 0 −50 −50 −25 0 25 50 75 100 2000 SW-Tr leak current (ILEAK) [pA] SW-Tr ON resister (RON) [Ω] 0.495 25 Topr vs. IFB (VFB = 0.5V) 5 0.500 0 Operating temperature (Topr) [°C] Topr vs. IDD (VFB = 0V) 0.505 500 Operating temperature (Topr) [°C] Operating temperature (Topr) [°C] 0.510 1000 Topr vs. ISTB (VCE = 0V) 700 100 0.515 1500 Operating temperature (Topr) [°C] 0 25 2000 −50 −25 FB pin input current (IFB) [pA] Quiescent current (IDD) [µA] 200 100 2500 Operating temperature (Topr) [°C] 800 300 75 3000 100 Topr vs. VTH 400 50 0 −50 −25 500 25 3500 1.5 100 0 Operating temperature (Topr) [°C] 0.0 0 200 Topr vs. TSS 2.0 Topr vs. ICE (VCE = VDD) 0 −50 −25 400 300 0 −50 −25 100 Standby current (ISTB) [pA] CE pin input voltage (VTH) [V] CE pin input current (ICE) [µA] 8 Operating temperature (Topr) [°C] Quiescent current (IDD) [µA] 0 2.5 9 25 500 Topr vs. Duty 10 0 600 Operating temperature (Topr) [°C] Operating temperature (Topr) [°C] 0 −50 −25 800 700 100 10 0 −50 −25 FB voltage (VFB) [V] Soft-start time (TSS) [µs] 1200 Maximum duty (Duty) [%] Switching frequency (fosc) [kHz] VDD = 3.6V, VSS = 0V unless otherwise noted −50 −25 0 25 50 75 100 Operating temperature (Topr) [°C] Topr vs. RON 1750 1500 1250 1000 750 500 250 0 −50 −25 0 25 50 75 100 Operating temperature (Topr) [°C] Topr vs. ILEAK SEIKO NPC CORPORATION —6 SM8121A OPERATION OVERVIEW L 10µH SBD VIN 2.3 to 5.5V CIN 4.7µF SW FB Buff VDD COUT 1.0µF LED ERR AMP PWM COMP ZD VREF RAMP GENERATOR Enable Disable CE OSC SOFT START VSS R1 The SM8121A basic structure is a step-up DC/DC converter. The booster control employs Pulse Width Modulation (PWM) which controls the pulse duty cycle (75% max.) at constant frequency (1.0MHz typ.). The LED current is set by a current-setting resistor R1 connected between pins FB (with stable voltage of 0.5V typ.) and VSS. When the switching transistor SW-Tr is ON, energy is stored in the inductor L. When SW-Tr is rapidly switched OFF, the energy stored in the inductor generates a voltage across the terminals of the inductor. The induced voltage, after being added to the input voltage, turns ON the Schottky barrier diode SBD and the stored energy is transferred to the output capacitor. This sequence of events continues repeatedly, boosting the output voltage. The SM8121A features a built-in soft-start function. The soft-start time is approximately 500µs from after the chip enable input CE rising edge. During this interval, the maximum duty is restricted to 50%. Selecting the Current-setting Resistor (R1) The SM8121A control stabilizes the voltage on pin FB (0.5V typ.). Hence, the current-setting resistor R1 connected between FB and VSS sets the LED current ILED, where the resistance R1 is given by the following equation. R1 = 0.5 / I LED FB VFB=0.5V ILED=0.5/R1 R1=0.5/ILED SEIKO NPC CORPORATION —7 SM8121A Selecting the Inductor (L) The recommended inductance for use with the SM8121A is 10µH. The inductor DC resistance affects the power efficiency, therefore a low DC resistance inductor is recommended. Note also that the peak inductor current Ipeak should not exceed the inductor maximum current rating. In pulsed current mode control, the peak inductor current Ipeak is given by the following equation. Ipeak = (VIN × TON) / L For example, if the input voltage VIN is 3.6V, the inductance L is 10µH, and the SW-Tr ON time T ON is 1MHz × 75% = 0.75µs, then the peak inductor current I peak is (3.6 × 0.75 × 10-6) / (10 × 10-6) = 0.27A = 270mA. Selecting the Capacitors (CIN, COUT) The recommended capacitances for use with the SM8121A are 4.7µF ceramic input capacitor C IN and 1.0µF ceramic output capacitor COUT. The capacitor ESR ratings affect the ripple voltage, therefore capacitors with low ESR rating are recommended. The input capacitor should be mounted close to the SM8121A IC. Note that the capacitor voltage ratings should be selected to provide sufficient margin for the applied input and output voltages. For example, if a lithium-ion battery (2.5 to 4.5V) is connected to the input and 3 white LEDs connected in series at the output draw 20mA, then the maximum input voltage is 4.5V and the maximum output voltage is (4.0V × 3 LEDs) + 0.5V = 12.5V. Therefore, the input capacitor should have a voltage rating of 6V, and the output capacitor should have a voltage rating of 16V. Selecting the Rectifier Schottky Barrier Diode (SBD) The rectifier schottky barrier diode forward-direction voltage drop affects the power efficiency, therefore a Schottky barrier diode with low forward-direction voltage drop is recommended. Note that the diode should be selected to provide sufficient margin for the rated current and reverse-direction withstand voltage. Board Layout Notes The following precautions should be followed for stable device operation. ■ ■ ■ ■ The inductor L and Schottky barrier diode SBD should be connected close to the pin SW using thick, short circuit wiring. The input capacitor CIN should be mounted close to the IC. The IC supply voltage VDD wiring and inductor supply wiring should be isolated, reducing any common impedances. The ground wiring should be connected at a single point, reducing any common impedances. SBD L SW VIN COUT LED VDD CIN CE FB VSS R1 SEIKO NPC CORPORATION —8 SM8121A LED OPEN-CIRCUIT PROTECTION When there is no load (LED open-circuit), the FB pin is pulled-down and then switching occurs at maximum duty. Consequently, the output voltage continues to be boosted and the SW pin voltage may exceed the maximum rating of 27V. A zener diode can be added so that it acts as the output load when the LED is open-circuit, preventing the SW voltage from rising. The zener diode must be selected so that the zener does not breakdown during normal operation. The zener voltage VZD range is given by the following relationship, where N is the number of LEDs connected in series, VF MAX is the maximum LED forward-bias voltage drop, VOUT MAX is the SW pin maximum output voltage, VFB is the FB pin voltage, and VSBD is the Schottky-barrier diode forward-bias voltage drop. (VF MAX × N) ≤ VZD ≤ (VOUT MAX − VFB − VSBD) When the load is applied using a connector (SM8121A and LEDs on separate boards), the zener diode should be mounted on the same board as the SM8121A device so that the SW boost prevention function can operate when the load is disconnected. Zener Diode (ZD) Only Connection When the load is removed (LEDs open circuit), the output voltage is determined by the zener voltage, and the output current is determined by the output current-setting resistance. Consequently, the output current when the load is removed is not limited, and thus the input current cannot be controlled. VOUT=VZD+0.5=15.5V SBD COUT 1.0µF IIN=(VOUT IZD)/VIN=65mA L 10µH SW VIN 3.6V CIN 4.7µF VSS VDD LED Open ZD (15V) SM8121 CE FB 33Ω IZD=0.5/33=15.15mA Zener Diode (ZD) and Current-Limiting Resistance Connection When the load is removed (LEDs open circuit), the output voltage is determined by the zener voltage, and the output current is determined by the sum of the output current-setting resistance and the current-limiting resistance. Consequently, the output current is limited when the load is removed, and the input current can be controlled. VOUT=VZD+0.5=15.5V SBD COUT 1.0µF IIN=(VOUT IZD)/VIN=2mA L 10µH SW VIN 3.6V CIN 4.7µF VSS FB VDD LED Open ZD (15V) SM8121 CE 1kΩ 33Ω IZD=0.5/1033=0.48mA SEIKO NPC CORPORATION —9 SM8121A BRIGHTNESS ADJUSTMENT Brightness Adjustment using FB Pin The LED brightness can be adjusted using an input DC control voltage connected through resistor R3 to the FB pin. Alternatively, the brightness can be controlled by a PWM signal by adding a low-pass filter comprising resistor R4 and capacitor C1. The PWM signal frequency range is determined by the low-pass filter coefficients. For example, the recommended values for resistor R4 (50kΩ) and capacitor C1 (0.1µF) provide a PWM signal frequency range of 1kHz to 1MHz. Brightness adjustment using FB pin (DC voltage input) 20 SBD COUT 1.0µF LED current [mA] 15 L 10µH SW VIN 3.6V CIN 4.7µF VSS VDD LED SM8121 CE FB 10 5 R2 20kΩ DC Voltage 0 to 3V R1 30Ω R3 100kΩ 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 DC voltage [V] Brightness adjustment circuit using FB pin (DC voltage input) DC voltage vs. LED current When the brightness is controlled by DC voltage (VDC) connected to resistor R3, the LED current (ILED) is given by equation 1. VFB − ILED = R2 × (VDC − VFB) R3 ... (1) R1 If the values R1 = 30Ω, R2 = 20kΩ, R3 = 100kΩ, VFB = 0.5V, and VDC = 0V are inserted in equation 1, the LED current ILED = 20mA, as shown in equation 2. 0.5 − ILED = 20,000 × (0 − 0.5) 100,000 30 = 0.6 = 20mA 30 ... (2) If the values R1 = 30Ω, R2 = 20kΩ, R3 = 100kΩ, VFB = 0.5V, and VDC = 3V are inserted in equation 1, the LED current ILED = 0mA, as shown in equation 3. 0.5 − ILED = 20,000 × (3 − 0.5) 100,000 30 = 0 = 0mA 30 ... (3) Taking the above diagram as an example, inserting the values R1 = 30Ω, R2 = 20kΩ, R3 = 100kΩ, VFB = 0.5V, and VDC = 0 to 3V into equation 1 gives the maximum LED current ILED of 20mA when VDC = 0V (equation 2) and the minimum LED current ILED of 0mA when VDC = 3V (equation 3). SEIKO NPC CORPORATION —10 SM8121A Brightness adjustment using FB pin (PWM signal input) SBD 20 COUT 1.0µF 15 SW VIN 3.6V CIN 4.7µF VSS LED current [mA] L 10µH VDD LED SM8121 CE FB 10 5 R3 50kΩ PWM signal Duty [%] R4 50kΩ R1 30Ω R2 20kΩ 0 C1 0.1µF 0.0 0.5 1.0 1.5 2.0 2.5 3.0 VPWM × Duty [V] VPWM [V] Brightness adjustment circuit using FB pin (PWM signal input) PWM signal vs. LED current When the brightness is controlled by PWM signal (VPWM × Duty), the LED current (ILED) is given by equation 4. VFB − ILED = R2 × (VPWM × Duty − VFB) R3 +R4 R1 ... (4) If the values R1 = 30Ω, R2 = 20kΩ, R3 = 50kΩ, R4 = 50kΩ, VFB = 0.5V, VPWM = 3V, and Duty = 0% are inserted in equation 4, the LED current ILED = 20mA, as shown in equation 5. 0.5 − ILED = 20,000 × (3 × 0 − 0.5) 50,000 + 50,000 30 = 0.6 = 20mA 30 ... (5) If the values R1 = 30Ω, R2 = 20kΩ, R3 = 50kΩ, R4 = 50kΩ, VFB = 0.5V, VPWM = 3V, and Duty = 100% are inserted in equation 4, the LED current ILED = 0mA, as shown in equation 6. 0.5 − ILED = 20,000 × (3 × 1 − 0.5) 50,000 + 50,000 30 = 0 = 0mA 30 ... (6) Taking the above diagram as an example, inserting the values R1 = 30Ω, R2 = 20kΩ, R3 = 50kΩ, R4 = 50kΩ, VFB = 0.5V, VPWM = 3V, and Duty = 0 to 100% into equation 4 gives the maximum LED current ILED of 20mA when Duty = 0% (equation 5) and the minimum LED current ILED of 0mA when Duty = 100% (equation 6). SEIKO NPC CORPORATION —11 SM8121A Brightness Adjustment using CE Pin The LED average current can be adjusted by controlling the duty of a PWM signal input on the CE pin. When CE goes from LOW to HIGH, the soft start function operates (with 500µs constant soft start time) and, therefore, the LED average current ratio for a given PWM signal duty falls with increasing PWM signal frequency. Taking this into consideration, the recommended PWM control signal has a frequency range of 100 to 400Hz with duty cycle range of 10 to 90%. 20.0 SBD 100Hz COUT 1.0µF Average LED current [mA] 15.0 L 10µH SW VIN 3.6V VSS CIN 4.7µF VDD LED SM8121 CE FB 10.0 1000Hz 1400Hz 5.0 R1 25Ω PWM signal 400Hz 0.0 0 10 20 30 40 50 60 70 80 90 100 PWM signal duty [%] Brightness adjustment circuit using CE pin PWM signal duty vs. LED average current When adjusting the brightness using the CE pin, a ripple voltage synchronized to the PWM signal is generated across the output capacitor COUT. The amplitude of the ripple voltage is determined by the number of LEDs and their forward-bias voltage drop characteristics. If a ceramic capacitor is used for the output capacitor COUT, an audible noise may be generated due to the ceramic capacitor’s piezoelectric effect. The audible noise level depends on the ceramic capacitor (capacitance, bias dependency, withstand voltage etc.), LEDs (number, forward-bias voltage drop etc.), and mounting board (thickness, mounting conditions etc.), and thus should be verified under actual conditions. Alternatively, a tantalum capacitor or film capacitor with low piezoelectric effect can be used as the output capacitor COUT to minimize the noise level, or the brightness can be adjusted using the FB pin as described earlier. The audible noise generated when using the CE pin is not an inherent phenomena of the SM8121A device, but of the brightness adjustment method employed. 11.0V 8.1V 3.5V COUT 20mA 3.5V 2.7V COUT 0mA 2.7V 3.5V 2.7V 0.5V 0V Output voltage with LEDs ON Output voltage with LEDs OFF CE input signal and output ripple voltage SEIKO NPC CORPORATION —12 SM8121A Current Switching using External Transistors If only a few brightness steps are required, the LED current can be adjusted by switching the LED current setting resistance using external transistors (Tr). SBD COUT 1.0µF L 10µH SW VIN 3.6V CIN 4.7µF VSS FB VDD LED SM8121 Select signal 1 ILED Low Low 2mA Low High 2 + 5 = 7mA High Low 2 + 12.5 = 14.5mA High High 2 + 5 + 12.5 = 19.5mA CE R3 40Ω Select signal 1 Select signal 2 Select signal 2 R2 100Ω R1 250Ω Tr1 Tr2 SEIKO NPC CORPORATION —13 SM8121A TYPICAL APPLICATION CIRCUITS 2 LEDs 3 LEDs SBD SBD COUT 1.0µF COUT 1.0µF L 10µH SW L 10µH ILED VDD SW ILED VDD LED SM8121 VSS CIN 4.7µF VIN LED VSS CIN 4.7µF VIN CE FB SM8121 CE FB R R 100 95 90 85 80 75 70 65 60 55 50 CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA) VIN=4.5V VIN=3.6V VIN=2.3V 0 5 10 15 Efficiency [%] Efficiency [%] CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA) 20 100 95 90 85 80 75 70 65 60 55 50 0 100 95 ILED=15mA 90 85 ILED=5mA 80 ILED=2mA 75 70 65 60 55 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Efficiency [%] Efficiency [%] 5 10 15 20 ILED [mA] ILED [mA] 100 95 ILED=15mA 90 ILED=5mA 85 80 ILED=2mA 75 70 65 60 55 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] VIN [V] 25 20 R=25Ω 15 R=33Ω 10 R=50Ω 5 R=100Ω ILED [mA] 25 ILED [mA] VIN=4.5V VIN=3.6V VIN=2.3V 20 R= 5Ω 15 R=33Ω 10 R=50Ω 5 R=100Ω R=250Ω R=250Ω 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] SEIKO NPC CORPORATION —14 SM8121A 4 LEDs 5LEDs SBD SBD COUT 1.0µF COUT 1.0µF L 10µH L 10µH SW ILED VDD SW ILED VDD LED LED VSS CIN 4.7µF VIN SM8121 VSS CIN 4.7µF VIN CE FB SM8121 CE FB R R 100 95 90 85 80 75 70 65 60 55 50 CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA) VIN=4.5V VIN=3.6V VIN=2.3V 0 5 10 15 Efficiency [%] Efficiency [%] CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA) 100 95 90 85 80 75 70 65 60 55 50 0 20 10 15 20 100 95 90 ILED=15mA 85 ILED=5mA 80 ILED=2mA 75 70 65 60 55 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 100 95 90 85 80 75 70 65 60 55 50 ILED=15mA ILED=5mA Efficiency [%] Efficiency [%] 5 ILED [mA] ILED [mA] ILED=2mA 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] VIN [V] 25 20 R=25Ω 15 R=33Ω 10 R=50Ω 5 R=100Ω R=250Ω 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] ILED [mA] 25 ILED [mA] VIN=4.5V VIN=3.6V VIN=2.3V 20 R=25Ω 15 R=33Ω 10 R=50Ω 5 R=100Ω R=250Ω 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] SEIKO NPC CORPORATION —15 SM8121A 6 LEDs SBD COUT 1.0µF L 6.8µH SW ILED VDD LED VSS CIN 4.7µF VIN SM8121 CE FB R Efficiency [%] CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH3N6R8K34 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA) 100 95 90 85 80 75 70 65 60 55 50 VIN=4.5V VIN=3.6V VIN=2.3V 0 5 10 15 20 Efficiency [%] ILED [mA] 100 95 90 ILED=15mA 85 ILED=5mA 80 ILED=2mA 75 70 65 60 55 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] ILED [mA] 25 20 R=25Ω 15 R=33Ω 10 R=50Ω 5 R=100Ω R=250Ω 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] SEIKO NPC CORPORATION —16 SM8121A EVALUATION BOARD PATTERN SOT23-5 package Pattern + Hole (Top view) Silk + Resist (Top view) Pattern + Hole (Bottom view) SON-6 package Pattern + Hole (Top view) Silk + Resist (Top view) Pattern + Hole (Bottom view) SEIKO NPC CORPORATION —17 SM8121A FOOTPRINT PATTERN SOT23-5 SON-6 0.7 2.10 2.4 1.0 0.75 0.25 0.5 0.95 SEIKO NPC CORPORATION —18 SM8121A Please pay your attention to the following points at time of using the products shown in this document. 1. The products shown in this document (hereinafter ”Products”) are designed and manufactured to the generally accepted standards of reliability as expected for use in general electronic and electrical equipment, such as personal equipment, machine tools and measurement equipment. The Products are not designed and manufactured to be used in any other special equipment requiring extremely high level of reliability and safety, such as aerospace equipment, nuclear power control equipment, medical equipment, transportation equipment, disaster prevention equipment, security equipment. The Products are not designed and manufactured to be used for the apparatus that exerts harmful influence on the human lives due to the defects, failure or malfunction of the Products. If you wish to use the Products in that apparatus, please contact our sales section in advance. In the event that the Products are used in such apparatus without our prior approval, we assume no responsibility whatsoever for any damages resulting from the use of that apparatus. 2. NPC reserves the right to change the specifications of the Products in order to improve the characteristics or reliability thereof. 3. The information described in this document is presented only as a guide for using the Products. No responsibility is assumed by us for any infringements of patents or other rights of the third parties which may result from its use. No license is granted by implication or otherwise under any patents or other rights of the third parties. Then, we assume no responsibility whatsoever for any damages resulting from that infringements. 4. The constant of each circuit shown in this document is described as an example, and it is not guaranteed about its value of the mass production products. 5. In the case of that the Products in this document falls under the foreign exchange and foreign trade control law or other applicable laws and regulations, approval of the export to be based on those laws and regulations are necessary. Customers are requested appropriately take steps to obtain required permissions or approvals from appropriate government agencies. SEIKO NPC CORPORATION 1-9-9, Hatchobori, Chuo-ku, Tokyo 104-0032, Japan Telephone: +81-3-5541-6501 Facsimile: +81-3-5541-6510 http://www.npc.co.jp/ Email:[email protected] ND14009-E-00 2014.06 SEIKO NPC CORPORATION - 19