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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
I I
PINOUT
(Top view)
I
I
I
I
I I I I I I I I I
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 (51: 9.8mA, 33: 15.2mA, 24: 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: 400A (typ) Standby current: 1.0A (max) RON (Switching MOS-Tr): 2 (typ) Switching frequency: 1.0MHz (typ) Output current detection accuracy: 2% Small package: SOT23-5 (SM8121AH) SON-6 (SM8121AD)
SOT23-5
SW
1
5
VDD
VSS
2
FB
3
4
CE
I
SON-6
APPLICATIONS
I I I I I I I I I
SW VSS VDD
1
6
FB VSS
Cellular phone Pager Digital still camera Handy terminal PDAs Portable games White LED drive LCD bias supply Flash memory supply
3
4
CE
ORDERING INFORMATION
Device SM8121AH SM8121AD Package SOT23-5 SON-6
NIPPON PRECISION CIRCUITS INC.--1
SM8121A
PACKAGE DIMENSIONS
(Unit: mm)
I
SOT23-5
0.20MIN + 0.2 1.6 - 0.1 + 0.2 2.8 - 0.3 1.9 0.2 2.9 0.2 0.4 0.1
+ 0.1 0.15 - 0.05
0.12 M 1.1 0.1 0 ~ 0.10
0.8 0.1
0.95 0.1
I
SON-6
0.2 0.1
2.6 0.1
3.0 0.1
( 0.3 ) ( 0.3 )
0.2 0.1
0.125 0.05
1.6 0.1
0.5
0.05 + 0.1 0.2 - 0.05
+ 0.1 0.75 - 0.05
0.3TYP
2.0
1.1
0.05 M
NIPPON PRECISION CIRCUITS INC.--2
SM8121A
BLOCK DIAGRAM
SW
FB VDD
Buff PWM COMP ERR AMP
VREF RAMP GENERATOR
CE
OSC SOFT START
VSS
PIN DESCRIPTION
Number Name SOT23-5 1 2 3 4 5 SON-6 1 2, 5 6 4 3 SW VSS FB CE VDD O - I Ip1 - Coil switching GND Feed back (Output current detection) Chip enable (High active) Power supply I/O Description
1. Input with built-in pull-down resistor
NIPPON PRECISION CIRCUITS INC.--3
SM8121A
SPECIFICATIONS
Absolute Maximum Ratings
Parameter Supply voltage range Input voltage range SW output voltage range SW input current Power dissipation Operating temperature range Storage temperature range Symbol VDD VIN VSW ISW PD Topr Tstg Rating -0.3 to 6.5 VSS - 0.3 to VDD + 0.3 -0.3 to 27 500 250 (Ta = 25C) -40 to 85 -55 to 125 Unit V V V mA mW C C
Electrical Characteristics
VDD = 3.6V, VSS = 0V, Ta = 25C unless otherwise noted
Rating Parameter Supply voltage Maximum output voltage Standby current Quiescent current SW-Tr ON resister SW-Tr leak current Switching frequency Maximum duty Input voltage Pin VDD SW VDD VDD SW SW SW SW CE CE Input current FB Soft-start time FB voltage Coil inductance SW FB SW Symbol VDD VOUT ISTB IDD RON ILEAK fOSC Duty VIH VIL ICE IFB TSS VFB LSW VCE = 3.6V VFB = 0.5V VCE = 0V VFB = 1.0V VFB = 0V ISW = 100mA, VDD = 3.6V VSW = VDD VFB = 0V VFB = 0V Condition min 2.3 - - - - - - 0.9 65 2.0 - - -1.0 - 0.49 - typ 3.6 - - 150 400 2.0 - 1.0 75 - - 5.0 - 500 0.50 - max 5.5 25 1.0 300 800 3.0 1.0 1.1 85 - 0.6 10 1.0 - 0.51 10 V V A A A A MHz % V V A A s V H Unit
NIPPON PRECISION CIRCUITS INC.--4
SM8121A
Typical Characteristics
VSS = 0V, Ta = 25C unless otherwise noted
100 90 80 70 60 50 40 30 20 10
0 2.5
1200
1000 900 Soft-start time (TSS) [s] 800 700 600 500 400 300 200 100 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Switching frequency (fosc) [kHz]
1000 800 600 400 200
Maximum duty (Duty) [%]
3.0 3.5 4.0 4.5 5.0 5.5 Supply voltage (VDD) [V]
0 Supply voltage (VDD) [V]
Supply voltage (VDD) [V]
VDD vs. fOSC
10 CE pin input current (ICE) [A] CE pin input voltage (VTH) [V] 9 8 7 6 5 4 3 2 1 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Supply voltage (VDD) [V] 2.5 2.0 1.5 1.0 0.5 0.0 2.5
VDD vs. Duty
200 Standby current (ISTB) [pA] 175 150 125 100 75 50 25 0 2.5
VDD vs. TSS
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
Supply voltage (VDD) [V]
Supply voltage (VDD) [V]
VDD vs. ICE (VCE = VDD)
500 800 700 600 500 400 300 200 100 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5
VDD vs. VTH
VDD vs. ISTB (VCE = 0V)
10 9 8 7 6 5 4 3 2 1 0 2.5
400 300 200 100 0 Supply voltage (VDD) [V]
FB pin input current (IFB) [pA]
Quiescent current (IDD) [A]
Quiescent current (IDD) [A]
3.0
3.5
4.0
4.5
5.0
5.5
3.0
3.5
4.0
4.5
5.0
5.5
Supply voltage (VDD) [V]
Supply voltage (VDD) [V]
VDD vs. IDD (VFB = 1.0V)
0.520 0.515
VDD vs. IDD (VFB = 0V)
5
VDD vs. IFB (VFB = 0.5V)
50
SW-Tr leak current (ILEAK) [pA]
2.5 3.0 3.5 4.0 4.5 5.0 5.5
SW-Tr ON resister (RON) []
FB voltage (VFB) [V]
0.510 0.505 0.500 0.495 0.490 0.485 0.480 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Supply voltage (VDD) [V]
4 3 2 1 0 Supply voltage (VDD) [V]
40 30 20 10 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Supply voltage (VDD) [V]
VDD vs. VFB
VDD vs. RON
VDD vs. ILEAK
NIPPON PRECISION CIRCUITS INC.--5
SM8121A VDD = 3.6V, VSS = 0V unless otherwise noted
1200
100
1000 900
Switching frequency (fosc) [kHz]
Maximum duty (Duty) [%]
1000 800 600 400 200 0 -50 -25
Soft-start time (TSS) [s]
90 80 70 60 50 40 30 20 10 0 -50 -25
800 700 600 500 400 300 200 100 0 -50 -25
0
25
50
75
100
0
25
50
75
100
0
25
50
75
100
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Topr vs. fOSC
10 2.5
Topr vs. Duty
3500 Standby current (ISTB) [pA] 3000 2500 2000 1500 1000 500 0
Topr vs. TSS
CE pin input current (ICE) [A]
9 8 7 6 5 4 3 2 1 0 -50 -25 0 25 50 75 100
CE pin input voltage (VTH) [V]
2.0 1.5 1.0 0.5 0.0 -50 -25 0 25 50 75 100 Operating temperature (Topr) [C]
-50 -25
0
25
50
75
100
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Topr vs. ICE (VCE = VDD)
500 800 700 600 500 400 300 200 100 0 0 25 50 75 100
Topr vs. VTH
Topr vs. ISTB (VCE = 0V)
500 450 400 350 300 250 200 150 100 50 0 -50 -50 -25
400 300 200 100 0 -50 -25
-50 -25
0
25
50
75
100
FB pin input current (IFB) [pA]
Quiescent current (IDD) [A]
Quiescent current (IDD) [A]
0
25
50
75
100
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Topr vs. IDD (VFB = 1.0V)
0.520 0.515 FB voltage (VFB) [V] 0.510 0.505 0.500 0.495 0.490 0.485 0.480 -50 -25 0 25 50 75 100 SW-Tr ON resister (RON) []
Topr vs. IDD (VFB = 0V)
5 SW-Tr leak current (ILEAK) [pA] -50 -25 4 3 2 1 0 0 25 50 75 100 Operating temperature (Topr) [C]
Topr vs. IFB (VFB = 0.5V)
2000 1750 1500 1250 1000 750 500 250 0 -50 -25 0 25 50 75 100
Operating temperature (Topr) [C]
Operating temperature (Topr) [C]
Topr vs. VFB
Topr vs. RON
Topr vs. ILEAK
NIPPON PRECISION CIRCUITS INC.--6
SM8121A
OPERATION OVERVIEW
L 10H
VIN 2.3 to 5.5V
SBD
CIN 4.7F
SW FB
ERR AMP
LED
COUT 1.0F
Buff
VDD
PWM COMP
ZD
VREF RAMP GENERATOR
Enable Disable CE VSS
OSC
SOFT START
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 500s 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 / ILED
FB VFB=0.5V
ILED=0.5/R1
R1=0.5/ILED
NIPPON PRECISION CIRCUITS INC.--7
SM8121A
Selecting the Inductor (L)
The recommended inductance for use with the SM8121A is 10H. 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 x TON) / L For example, if the input voltage VIN is 3.6V, the inductance L is 10H, and the SW-Tr ON time T ON is 1MHz x 75% = 0.75s, then the peak inductor current I peak is (3.6 x 0.75 x 10-6) / (10 x 10-6) = 0.27A = 270mA.
Selecting the Capacitors (CIN, COUT)
The recommended capacitances for use with the SM8121A are 4.7F ceramic input capacitor C IN and 1.0F 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 x 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.
I
I I
I
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 CIN
COUT
LED
VDD CE VSS FB
R1
NIPPON PRECISION CIRCUITS INC.--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 x 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
COUT 1.0F
SBD
IIN=(VOUT IZD)/VIN=65mA
L 10H SW VDD SM8121 ZD (15V) CE LED Open
VIN 3.6V
CIN 4.7F
VSS
FB
33
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
COUT 1.0F
SBD
IIN=(VOUT IZD)/VIN=2mA
L 10H SW VDD SM8121 ZD (15V) CE 1k 33
IZD=0.5/1033=0.48mA CIN 4.7F
VIN 3.6V
LED Open
VSS
FB
NIPPON PRECISION CIRCUITS INC.--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 (50k) and capacitor C1 (0.1F) provide a PWM signal frequency range of 1kHz to 1MHz. Brightness adjustment using FB pin (DC voltage input)
20
SBD
COUT 1.0F
L 10H SW VSS SM8121 VDD
LED
15 LED current [mA]
R1 30
10
VIN 3.6V
CIN 4.7F
FB
CE R2 20k
5
DC Voltage 0 to 3V
R3 100k
0 0.0 0.5 1.0 1.5 DC voltage [V] 2.0 2.5 3.0
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.
R2 x (VDC - VFB) R3 R1
VFB - ILED =
... (1)
If the values R1 = 30, R2 = 20k, R3 = 100k, 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 x (0 - 0.5) 100,000 30
=
0.6 = 20mA 30
... (2)
If the values R1 = 30, R2 = 20k, R3 = 100k, 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 x (3 - 0.5) 100,000 30
=
0 = 0mA 30
... (3)
Taking the above diagram as an example, inserting the values R1 = 30, R2 = 20k, R3 = 100k, 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).
NIPPON PRECISION CIRCUITS INC.--10
SM8121A Brightness adjustment using FB pin (PWM signal input)
SBD
20
COUT 1.0F
SW VSS SM8121
VDD
LED
LED current [mA]
R1 30
L 10H
15
VIN 3.6V
CIN 4.7F
10
FB
CE
5
R3 50k R4 50k R2 20k
PWM signal Duty [%]
VPWM [V]
C1 0.1F
0 0.0 0.5 1.0 1.5 VPWM x Duty [V] 2.0 2.5 3.0
Brightness adjustment circuit using FB pin (PWM signal input)
PWM signal vs. LED current
When the brightness is controlled by PWM signal (VPWM x Duty), the LED current (ILED) is given by equation 4.
R2 x (VPWM x Duty - VFB) R3 +R4 R1
VFB - ILED =
... (4)
If the values R1 = 30, R2 = 20k, R3 = 50k, R4 = 50k, 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 x (3 x 0 - 0.5) 50,000 + 50,000 30
=
0.6 = 20mA 30
... (5)
If the values R1 = 30, R2 = 20k, R3 = 50k, R4 = 50k, 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 x (3 x 1 - 0.5) 50,000 + 50,000 30
=
0 = 0mA 30
... (6)
Taking the above diagram as an example, inserting the values R1 = 30, R2 = 20k, R3 = 50k, R4 = 50k, 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).
NIPPON PRECISION CIRCUITS INC.--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 500s 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 1.0F
15.0 Average LED current [mA]
400Hz
L 10H SW VSS SM8121 VDD
LED
10.0 1000Hz 5.0 1400Hz
VIN 3.6V
CIN 4.7F
FB
CE
PWM signal
R1 25
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
COUT
20mA
3.5V 3.5V 3.5V 0.5V
COUT
0mA
2.7V 2.7V 2.7V 0V
Output voltage with LEDs ON
Output voltage with LEDs OFF
CE input signal and output ripple voltage
NIPPON PRECISION CIRCUITS INC.--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 1.0F
L 10H SW VSS SM8121 VDD
LED
Select signal 2 Low Low
Select signal 1 Low High Low High 2mA
ILED
VIN 3.6V
CIN 4.7F
2 + 5 = 7mA 2 + 12.5 = 14.5mA 2 + 5 + 12.5 = 19.5mA
FB
CE
High
R3 40 Select signal 1 Select signal 2 Tr2 R2 100 Tr1 R1 250
High
NIPPON PRECISION CIRCUITS INC.--13
SM8121A
TYPICAL APPLICATION CIRCUITS
2 LEDs
SBD
3 LEDs
SBD
COUT 1.0F
L 10H
SW VDD LED
COUT 1.0F
L 10H
SW
ILED
VDD
LED SM8121
ILED
VIN
CIN 4.7F
VSS
SM8121
VIN
CE
CIN 4.7F
VSS
FB
FB
CE
R
R
CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA)
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 5 10 ILED [mA] 15 20
Efficiency [%]
Efficiency [%]
VIN=4.5V VIN=3.6V VIN=2.3V
100 95 90 85 80 75 70 65 60 55 50 0
VIN=4.5V VIN=3.6V VIN=2.3V
5
10 ILED [mA]
15
20
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 VIN [V]
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]
Efficiency [%]
Efficiency [%]
25 20 ILED [mA] 15 10 5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] R=25 ILED [mA] R=33 R=50 R=100 R=250
25 20 15 10 5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] R= 5 R=33 R=50 R=100 R=250
NIPPON PRECISION CIRCUITS INC.--14
SM8121A
4 LEDs
SBD
5LEDs
SBD
COUT 1.0F
L 10H
SW VDD LED
COUT 1.0F
L 10H
ILED
SW VDD LED
ILED
VIN
CIN 4.7F
VSS
SM8121
VIN
FB CE
CIN 4.7F
VSS
SM8121
FB
CE
R
R
CIN: 2012Y5VIC 475Z (TDK) COUT: 2012Y5VIH 105Z (TDK) L: LQH32CN100K11 (Murata) SBD: RB551V-30 (ROHM) LED: NSCW455 (NICHIA)
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 5 10 ILED [mA] 15 20
Efficiency [%]
Efficiency [%]
VIN=4.5V VIN=3.6V VIN=2.3V
100 95 90 85 80 75 70 65 60 55 50 0 5 10 ILED [mA] 15 20
VIN=4.5V VIN=3.6V VIN=2.3V
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]
100 95 90 85 80 75 70 65 60 55 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V]
Efficiency [%]
Efficiency [%]
ILED=15mA ILED=5mA ILED=2mA
25 20 ILED [mA] 15 10 5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] R=25 ILED [mA] R=33 R=50 R=100 R=250
25 20 15 10 5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] R=25 R=33 R=50 R=100 R=250
NIPPON PRECISION CIRCUITS INC.--15
SM8121A
6 LEDs
SBD
COUT 1.0F
L 6.8H
SW VDD LED
ILED
VIN
CIN 4.7F
VSS
SM8121
FB
CE
R
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 0 5 10 ILED [mA] 15 20
Efficiency [%]
VIN=4.5V VIN=3.6V VIN=2.3V
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]
Efficiency [%]
25 20 ILED [mA] 15 10 5 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN [V] R=25 R=33 R=50 R=100 R=250
NIPPON PRECISION CIRCUITS INC.--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)
NIPPON PRECISION CIRCUITS INC.--17
SM8121A
FOOTPRINT PATTERN
SOT23-5 SON-6
0.7
0.25
0.75
1.0
0.5
0.95
NIPPON PRECISION CIRCUITS INC.--18
2.10
2.4
SM8121A
Please pay your attention to the following points at time of using the products shown in this document. The products shown in this document (hereinafter "Products") are not intended to be used for the apparatus that exerts harmful influence on human lives due to the defects, failure or malfunction of the Products. Customers are requested to obtain prior written agreement for such use from NIPPON PRECISION CIRCUITS INC. (hereinafter "NPC"). Customers shall be solely responsible for, and indemnify and hold NPC free and harmless from, any and all claims, damages, losses, expenses or lawsuits, due to such use without such agreement. NPC reserves the right to change the specifications of the Products in order to improve the characteristic or reliability thereof. NPC makes no claim or warranty that the contents described in this document dose not infringe any intellectual property right or other similar right owned by third parties. Therefore, NPC shall not be responsible for such problems, even if the use is in accordance with the descriptions provided in this document. Any descriptions including applications, circuits, and the parameters of the Products in this document are for reference to use the Products, and shall not be guaranteed free from defect, inapplicability to the design for the mass-production products without further testing or modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any entity not in compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are requested appropriately take steps to obtain required permissions or approvals from appropriate government agencies. NIPPON PRECISION CIRCUITS INC. 4-3, Fukuzumi 2-chome, Koto-ku, Tokyo 135-8430, Japan Telephone: +81-3-3642-6661 Facsimile: +81-3-3642-6698 http://www.npc.co.jp/ Email: sales@npc.co.jp
NC0211DE 2004.01
NIPPON PRECISION CIRCUITS INC.--19

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