SM8134A White LED Driver IC OVERVIEW The SM8134A is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in parallel and 1 flash white LED, making the device ideal for camera-equipped cellular phones. The charge pump switches between ×1 to ×1.5 boost mode in response to LED drive current requirements to extend battery life to the maximum. The boost switching occurs in response to the drive current of all the connected LED and thus supports variations in LED forward-bias voltage drop (VF). Each LED drive current is controlled by a 5-channel LED drive current control circuit. The backlight LED drive current and ON/OFF control, and flash LED drive current and ON/OFF control are all set by 3-wire serial interface data input. Also, an under voltage lockout (UVLO) circuit is built-in to prevent incorrect operation when the battery voltage drops. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ GND DIN2 EN SCK PACKAGE DIMENSION (Unit: mm) TOP VIEW 3.0 ± 0.08 BOTTOM VIEW 1.8 B A 1.8 ■ ■ 3 = 1.5 ± 0.05 ■ 0.3 ± 0.1 ■ SDA DIN1 VOUT VIN 0.5 ■ DIN3 DIN4 DIN5 PGND C1P C1M C2M C2P ■ 3.0 ± 0.08 ■ (Top view) C 0.3 0.2 S A B S 0.22 ± 0.05 ∆ 0.05 M S A B 0.2 S 0.05 S 0.5 0.7 ± 0.05 ■ Noise reduction due to charge pump boost circuit Automatic charge pump switching to conserve power Drives 1 to 4 backlight white LED (30mA/ch at maximum setting) Drives a flash white LED (150mA at maximum setting) Backlight and flash white LED brightness adjustment 3-wire serial input interface for all setting and control Under voltage lockout (UVLO) circuit built-in Soft start circuit built-in Thermal protection circuit built-in Input voltage range • No-load current (IOUT = 0mA): 2.7 to 4.6V • Load current (IOUT = 80mA): 3.0 to 4.6V • Load current (IOUT = 180mA): 3.3 to 4.6V • Load current (IOUT = 200mA): 3.4 to 4.6V Quiescent current • Not-switching (×1.0 mode): 0.3mA (typ) • Switching (×1.5 mode): 1.7mA (typ) Standby current: 0.01µA (typ) Operating frequency: 750kHz (typ) Maximum backlight LED current: 30mA/ch Maximum flash LED current: 150mA All LED total maximum current: 200mA Backlight LED current matching (ILED = 20mA) : ± 3% Flash LED current accuracy (ILED = 150mA) : ± 6.7% Packages: 16-pin QFN 0.2 ± 0.05 ■ PINOUT 0.1 ± 0.05 FEATURES APPLICATIONS ■ ■ ■ ■ Cellular phone Digital still camera PDA Portable games ORDERING INFORMATION Device Package SM8134AB 16-pin QFN SEIKO NPC CORPORATION —1 SM8134A BLOCK DIAGRAM VIN C1M C1P C2M C2P Charge pump 1/ 1.5 VOUT Thermal shut down Output voltage control DIN1 UVLO DIN2 Current control & Current detect SCK DIN3 DIN4 Control logic SDA DIN5 EN GND PGND PIN DESCRIPTION Number Name I/O Description 1 C1P – Charge pump capacitor connection 1P 2 C1M – Charge pump capacitor connection 1M 3 C2M – Charge pump capacitor connection 2M 4 C2P – Charge pump capacitor connection 2P 5 VIN – Voltage supply 6 VOUT O LED drive voltage output 7 DIN1 O LED drive current control output 1 (connect to ground when not used) 8 SDA I Serial data input 9 SCK I Serial data clock input 10 EN I Serial interface enable input 11 DIN2 O LED drive current control output 2 (connect to ground when not used) 12 GND – Ground 13 DIN3 O LED drive current control output 3 (connect to ground when not used) 14 DIN4 O LED drive current control output 4 (connect to ground when not used) 15 DIN5 O LED drive current control output 5 (connect to ground when not used) 16 PGND – Charge pump ground connection SEIKO NPC CORPORATION —2 SM8134A SPECIFICATIONS Absolute Maximum Ratings GND = PGND = 0V Note. The device may suffer breakdown if any one of these parameter ratings is exceeded. Parameter Symbol Rating Unit VIN −0.3 to 5.5 V VEN, VSCK, VSDA –0.3 to VIN + 0.3 V VDIN1 to 5 –0.3 to VIN + 0.3 V VOUT 5.5 V IOUT 500 mA PD 800 (Ta = 25°C)*1 mW TJMAX +125 °C Tstg −55 to +125 °C Supply voltage range Input voltage range Output voltage range VOUT output current Power dissipation Junction temperature Storage temperature range *1. When mounted on a 4-layer PCB. 800 Power dissipation [mW] 800 640 600 480 400 320 200 0 25 35 45 55 65 75 85 Operating temperature [°C] Recommended Operating Conditions GND = PGND = 0V Rating Parameter Supply voltage range Input voltage range Ambient temperature range Pin Symbol Conditions Unit min typ max VIN1 ×1.0 mode, IOUT = 0mA 2.7 3.6 4.6 V VIN2 ×1.5 mode, IOUT = 80mA, VF = 3.5V*1 3.0 3.6 4.6 V VIN3 ×1.5 mode, IOUT = 180mA, VF = 3.5V*1 3.3 3.6 4.6 V VIN4 ×1.5 mode, IOUT = 200mA, VF = 3.5V*1 3.4 3.6 4.6 V EN, SCK, SDA VES Each logic-level pin 0 − VIN V − Ta −30 − +85 °C VIN *1. The maximum value of VF in the drive LED SEIKO NPC CORPORATION —3 SM8134A Electrical Characteristics DC Characteristics GND = 0V, VIN = 3.6V, Ta = 25°C unless otherwise noted. Rating Parameter Pin Standby current VIN Quiescent current VIN Symbol Condition Unit min typ max ISTB Standby mode – 0.01 1.00 µA IDD1 ×1.0 mode, no load – 0.3 1.0 mA IDD2 ×1.5 mode, no load – 1.7 4.0 mA Maximum output voltage VOUT VOUT ×1.5 mode VOUT maximum voltage 4.6 4.9 5.2 V Maximum output current VOUT IOUT ×1.5 mode 200 – – mA Operating frequency C1M fOSC ×1.5 mode switching frequency 650 750 850 kHz Internal circuit power-ON reset time*1 VIN TPOR Time from when power is applied until internal circuit reset – 0.05 1.0 ms Soft start time DIN1 to 5 TSS Time between EN signal falling edge and LED turning ON – 1.0 3.0 ms LED drive pin leakage current DIN1 to 5 ILEAK1 to 5 Standby mode, VDIN1 to 5 = VIN – 0.01 1.00 µA LED drive current matching DIN1 to 4 ∆ ILED ×1.0 mode, matching between channels with ILED1 to 4 = 20mA setting –3.0 – +3.0 % LED drive current 1 DIN1 to 4 ILED1 to 4 ×1.0 mode, ILED1 to 4 = 20mA setting 19.0 20.0 21.0 mA LED drive pin voltage 1*2 DIN1 to 4 VDIN1 to 4 ILED1 to 4 = 20mA setting – 160 – mV LED drive current 2 DIN5 ILED5 ×1.5 mode, ILED5 maximum setting 140 150 160 mA LED drive pin voltage 2*2 DIN5 VDIN5 IDIN5 maximum setting – 400 – mV Under voltage lockout threshold*3 – VUV VIN falling 1.6 1.9 2.2 V Thermal protection circuit operating temperature*1 – TSD – 170 – °C Thermal protection circuit hysteresis*1 – TSDHYS – 20 – °C EN, SCK, SDA VIH HIGH-level input voltage range 1.8 – – V Logic-level input voltage VIL LOW-level input voltage range – – 0.6 V EN, SCK, SDA IIL EN = SCK = SDA = VIN – – 1.0 µA IIH EN = SCK = SDA = GND –1.0 – – µA Logic-level input current *1. Design guaranteed value *2. Pin voltage value which switching ×1.0 mode to ×1.5 mode when LED current shortage detection *3. When UVLO is active, the output is stopped and internal register is reset. SEIKO NPC CORPORATION —4 SM8134A AC Characteristics GND = 0V, VIN = 3.6V, Ta = 25°C unless otherwise noted. Rating Parameter Symbol Condition Unit min typ max SCK clock cycle tSCK 2000 – DC ns SCK HIGH-level pulse width tWH 800 – – ns SCK LOW-level pulse width tWL 800 – – ns EN setup time tCS 1000 – – ns EN hold time tCH 800 – – ns EN recovery time tCR 1000 – – ns Write data setup time tDS 600 – – ns Write data hold time tDH 600 – – ns EN tCS tCR tWL SCK tWH tCH tSCK tDH tDS SDA Data input timing diagram SEIKO NPC CORPORATION —5 SM8134A VOUT EFFICIENCY VOUT power efficiency [%] 100 90 VF = 3.2V 80 VF = 3.4V VF = 3.6V VF=3.8V 70 60 50 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.4 4.6 VIN [V] Efficiency of PIN vs. POUT Backlight LED × 4pcs, ILED1 to 4 = 20mA, Flash LED × 1pc, ILED5 = 0mA, IOUT = 80mA VOUT power efficiency [%] 100 90 VF = 3.2V VF = 3.4V 80 VF = 3.6V VF=3.8V 70 60 50 3.2 3.4 3.6 3.8 4.0 4.2 VIN [V] Efficiency of PIN vs. POUT Backlight LED × 3pcs, ILED1 to 4 = 16mA, Flash LED × 1pc, ILED5 = 0mA, IOUT = 48mA SEIKO NPC CORPORATION —6 SM8134A VOUT power efficiency [%] 100 90 80 VF = 3.2V VF = 3.4V VF = 3.6V 70 VF=3.8V 60 50 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 VIN [V] Efficiency of PIN vs. POUT Backlight LED × 4pcs, ILED1 to 4 = 20mA, Flash LED × 1pc, ILED5 = 120mA, IOUT = 200mA VOUT power efficiency [%] 100 90 80 VF = 3.2V VF = 3.4V VF = 3.6V 70 VF=3.8V 60 50 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 VIN [V] Efficiency of PIN vs. POUT Backlight LED × 3pcs, ILED1 to 4 = 16mA, Flash LED × 1pc, ILED5 = 150mA, IOUT = 198mA SEIKO NPC CORPORATION —7 SM8134A FUNCTIONAL DESCRIPTION Serial Interface The SM8134A uses a 3-wire serial interface to control each setting. Input data on SDA is input MSB first in an 8 clock pulse cycle structure, with the first 4 cycles of data setting the mode and the next 4 the corresponding mode data. Data bits on SDA are read as received data on the rising edges of the SCK clock after EN goes HIGH. Only the leading 8 bits on SDA are read after EN goes HIGH and all subsequent input data bits are ignored, but the received data is reflected in SM8134A operation with timing almost simultaneous with the EN falling edge. Conversely, if less than 8 bits are input on SDA, the data is ignored to prevent incorrect operation. All registers are write-only, and their status cannot be read. After power is applied, an internal power-ON reset circuit initializes all registers to logic level LOW in standby mode. However, the possibility exists that there may be insufficient reset time, depending on the VIN input voltage rise time and fall time, so reset mode (0H or EH) should be expressly invoked after power is applied. There is no restriction in the input sequence when setting parameters. However, since the parameters are set in the same order as the data input sequence and the time taken from LED ON/OFF data input to LED dimming data input can exceed the soft start time, it is highly advisable to enter the LED dimming data first. The charge pump circuit, that supplies the LED drive voltage, starts whenever any parameter in address 5H (LED ON register) is set to 1, with the LED drive voltage output on VOUT. Conversely, when all parameters in address 5H are set to 0, all other parameter data settings input after reset are retained in standby mode. The serial interface pins EN, SDA, and CSK are CMOS inputs, thus the input voltage on VIN must be a logic-level voltage and should not be left open circuit (floating). Control Data Mode selection data Setting data M1 M2 M3 M4 D1 D2 D3 D4 MSB Data 1 Data 2 Data 3 Data 4 Data 5 Data 6 LSB EN SCK SDA M1 M2 M3 M4 D1 D2 D3 D4 Control data input sequence ■ Mode selection Mode data 0H 2H 4H 5H EH Other Mode Reset DIN1 to 4 dimming DIN5 dimming LED ON Reset NPC test M1-M2-M3-M4 L-L-L-L L-L-H-L L-H-L-L L-H-L-H H-H-H-L − SEIKO NPC CORPORATION —8 SM8134A Mode data “0H”: Reset register Mode data “EH”: Reset register Setting data D1 D2 D3 D4 High All system data reset and standby Low Reset mode is selected if EN goes LOW 4 clock cycles after 0H or EH mode select data is input, regardless of when power is applied or the parameter set data bits. When reset mode is selected, all data input previously is reset, thus dimming and control data must be reentered. Mode data “2H”: DIN1 to 4 dimming register Mode data “4H”: DIN5 dimming register Setting data D1 D2 D3 D4 DIN1 to 4 DIN5 Unit 0H Low Low Low Low 0 0 mA 1H Low Low Low High 2 10 mA 2H Low Low High Low 4 20 mA 3H Low Low High High 6 30 mA 4H Low High Low Low 8 40 mA 5H Low High Low High 10 50 mA 6H Low High High Low 12 60 mA 7H Low High High High 14 70 mA 8H High Low Low Low 16 80 mA 9H High Low Low High 18 90 mA AH High Low High Low 20 100 mA BH High Low High High 22 110 mA CH High High Low Low 24 120 mA DH High High Low High 26 130 mA EH High High High Low 28 140 mA FH High High High High 30 150 mA Note. “H”: Hexadecimal Note. Target values only. Current rating accuracy is not guaranteed. D1 to D4 setting data bits control the LED current in 15 steps. Mode data “5H”: LED ON register Setting data D1 D2 D3 D4 High DIN1 to 4 ON − DIN5 ON − Low DIN1 to 4 OFF − DIN5 OFF − This register controls the DIN1 to 4 and DIN5 ON/OFF state. Each state is ON when the corresponding bit is HIGH, and OFF when LOW. Each circuit starts when the corresponding bit in address 5H (D1 or D3) is set HIGH, transferring from standby mode. It is recommended that these data settings be held LOW when possible to control current consumption. SEIKO NPC CORPORATION —9 SM8134A Thermal Shutdown Circuit (Overheating Protection) The thermal shutdown circuit operates whenever the IC temperature exceeds approximately 170°C for whatever reason. VOUT output recommences when the IC temperature falls below approximately 150°C. In that case, the setting register is saved. Under Voltage Lockout Circuit (UVLO) When a VIN voltage falls below the 1.9V (typ), the under voltage lockout circuit operates, initializing all the registers to logic 0. In this mode, all previous data is reset, thus all dimming and LED control data must be input again. VOUT Output Circuit Mode Switching The SM8134A switches between 3 output states: standby mode (standby state), ×1.0 mode (VIN through mode), and ×1.5 mode (×1.5 charge pump boost). This automatically adjusts the VOUT output to match the drive LED characteristics and reduces the total power dissipation. Switching to and from ×1.0 and ×1.5 mode occurs automatically in an internal circuit, and cannot be controlled using an external input. Switching to standby mode The internal circuit operating mode switches from ×1.0/×1.5 mode to standby mode when Reset resistor (mode data “0H”, “EH”) was input, suppressing current consumption. Switching from ×1.0 mode to ×1.5 mode If the LED drive current set by serial interface can be driven without boosting the VIN input voltage, the VOUT output operates in ×1.0 mode. In other words, if sufficient current flows even with the LED forward-direction voltage drop “VF”, then VOUT is less than 4.9V. Operation in the more efficient ×1.0 mode reduces the total power dissipation and extends the battery drive time. And if low “VF” LEDs are used or the LED drive current setting is LOW, the operating time in ×1.0 mode is also extended. 1.0 mode (high efficiency) 1.5 mode (low efficiency) 1.0 mode (high efficiency) 1.5 mode (low efficiency) High VF LED Low VF LED High VIN input Low VOUT mode switching time comparison due to drive LED “VF” variation If the VIN voltage falls or LED drive current set by serial interface increases such that the LED drive current is too low in ×1.0 mode, then the LED drive circuit low-current detector operates, the VOUT output is automatically switched to ×1.5 mode, and the charge pump boosts the output voltage. This occurs even if only one LED low-current condition is detected among the 5-channel LED drive circuits, thus it is recommended that LEDs have small “VF” variation to optimize the total efficiency. SEIKO NPC CORPORATION —10 SM8134A VIN input voltage 1.0 Low ILED detector 1.5 threshold (1) Low ILED detected VOUT mode (2) 1.0 mode 1.5 mode 4.9V VOUT output voltage (3) VIN voltage drop and VOUT output voltage (1) When VIN falls, VOUT cannot overcome the LED “VF” rating, causing insufficient current flows and the ILED low-current signal becomes active. (2) When the ILED low-current condition is detected, the VOUT output circuit switches to ×1.5 mode (charge pump mode). (3) Prior to switching to ×1.5 mode, the VOUT voltage may be lower than 4.9V but sufficient current is supplied to the LED. If after startup, the LED connected to a DIN pin is switched, the LED connection detector circuit flags an error, and correct mode switching may not occur. If the DIN pin does not control the LED drive current, the low-current detector does not operate and the device cannot switch to ×1.5 mode. SEIKO NPC CORPORATION —11 SM8134A Switching from ×1.5 mode to ×1.0 mode VF increases immediately after the LED current starts to flow, and then decreases as the LED temperature increases due to the heating effect of the current flow. It can take about 10 seconds for the LED temperature to stabilize and for VF to reach equilibrium, and VF may fluctuate more than 200mV. The VF fluctuation is affected by the ambient temperature and LED current setting, and has a large affect on the automatic mode switching voltage tolerances. To counter the effects of VF fluctuation, the SM8134A outputs a mode reset signal once every 1.4 seconds which automatically switches the output mode to ×1.0, and then a determination is made whether to make the ×1.0 → ×1.5 mode switch. 1.4sec/cycle (1) Mode reset (2) VOUT mode 1.5 mode Mode hold L: hold 1.0 mode min 80µs max 200µs (3) ILED detector ignore VOUT output voltage 4.9V (4) Low ILED detector (5) Switching from ×1.5 to ×1.0 mode due to the mode reset signal (1) Mode reset signal is output once every 1.4 seconds. (2) Switching from ×1.5 to ×1.0 mode due to the mode reset signal pulse. (3) The mode hold time of 200µs (max) starts when output switches to ×1.0 mode. During this interval, the mode is not switched even if an ILED undercurrent condition is detected. (4) If VIN is low, the VOUT voltage momentarily drops because the boost function stops as a result of switching to ×1.0 mode. (5) The ILED undercurrent signal is ignored during the mode hold time, and the mode only switches in response to the detector output after the mode hold time expires. SEIKO NPC CORPORATION —12 SM8134A For example, if the VIN voltage is low and the VOUT output voltage in ×1.0 mode does not provide sufficient drive current, then the mode reset will cause a LED undercurrent condition. The LED undercurrent detector circuit will output an LED undercurrent signal immediately after the switch to ×1.0 mode, but the output will stay in ×1.0 mode and not return to ×1.5 mode for the duration of the mode hold time. Consequently, the VOUT output is not boosted during the 85µs (min) to 200µs (max) mode hold time and the voltage drops and the LED brightness is reduced. However, the LEDs are OFF for a maximum of 200µs only, and this is not discernible to the naked eye and thus is not a problem. 1.0 1.5 threshold VIN input voltage Mode reset (1.4sec/cycle) Mode hold (H: hold) 1.4sec max 200µS VOUT mode (H: 1.5, L: 1.0) 4.9V VOUT output voltage Low ILED detector (H: low ILED) VOUT drop due to the mode reset single SEIKO NPC CORPORATION —13 SM8134A STARTUP SEQUENCE After power is applied to the SM8134A or when a reset input occurs (reset register mode setting), the internal power-ON reset circuit initializes all registers to their default value of 0. Consequently, all required data for LED drive operation must be input using the serial interface. The registers can be addressed in arbitrary sequence. Note that the registers are set in the same sequence as they are addressed. Example 1. Set LED1 to LED4 to 20mA drive without group setting Set EN HIGH, input “2AH” using the serial interface, set EN LOW (LED1 to 4 current setting 20mA), set EN HIGH, input “58H”, set EN LOW, LED1 to LED4 turn ON after the soft start ends. Set LED1 to 4 current 20mA LED1 to 4 ON EN 2 SDA 0 0 A 1 0 1 0 5 1 0 0 1 8 0 1 1 0 0 0 SCK Soft start time LED1 to 4 20mA EN = High Send serial data "2AH" 2: DIN1 to 4 dimming command A: Dimming data (20mA) EN = Low EN = High Send serial data "58H" 5: LED ON command 8: LED1 to 4 ON EN = Low Example 1 input waveform SEIKO NPC CORPORATION —14 SM8134A Example 2. Set LED1 to LED4 to 20mA and LED5 to 120mA drive Input “2AH” (LED1 to 4 current setting 20mA), “4CH” (LED5 current setting 120mA), “58H” (LED1 to 4 ON) on successive EN cycles using the serial interface. LED1 to LED4 turn ON after the soft start ends. Then input “5AH” (LED1 to 5 ON) and in addition to LED1 to LED4, LED5 turns ON. Set LED1 to 4 current 20mA Set LED5 current 120mA LED1 to 4 ON LED1 to 5 ON EN 2 SDA 0 0 A 1 0 1 0 5 1 0 0 1 8 0 1 1 0 4 0 0 0 1 C 0 0 1 1 5 0 0 0 1 A 0 1 1 0 1 0 SCK 20mA LED1 to 4 Soft start time 120mA LED5 Soft start time EN = High Send serial data "2AH" 2: DIN1 to 4 dimming command A: Dimming data (20mA) EN = Low EN = High Send serial data "58H" 5: LED ON command 8: LED1 to 4 ON EN = Low EN = High Send serial data "4CH" 4: DIN5 dimming command C: Dimming data (120mA) EN = Low EN = High Send serial data "5AH" 5: LED ON command A: LED1 to 4 ON, LED5 ON EN = Low Example 2 input waveform SEIKO NPC CORPORATION —15 SM8134A Example 3. Set LED1 to LED4 to 30mA drive, and then change LED 1 to LED4 to12mA drive and set LED5 to 150mA drive Input “2FH” (LED1 to 4 current setting 30mA) and “58H” (LED1 to 4 ON) using the serial interface. LED1 to LED4 turn ON after the soft start ends. Then input “26H” (LED1 to 4 current setting 12mA), the current of LED1 to LED4 change to 12mA. Moreover input “4FH” (LED5 current setting 150mA) and “5AH” (LED1 to 5 ON), LED5 turns ON in addition to LED1 to LED4. The total current of LED1 to LED5 should be set not exceeding 200mA. Set LED1 to 4 current 30mA Set LED1 to 4 current 12mA LED1 to 4 ON Set LED5 current 150mA LED1 to 5 ON EN 2 SDA 0 0 F 1 0 1 1 5 1 1 0 1 8 0 1 1 0 2 0 0 0 0 6 1 0 0 1 4 1 0 0 1 F 0 0 1 1 5 1 1 0 1 A 0 1 1 0 1 0 SCK 30mA LED1 to 4 12mA Soft start time 150mA LED5 Soft start time EN = High Send serial data "2FH" 2: DIN1 to 4 dimming command F: Dimming data (30mA) EN = Low EN = High Send serial data "58H" 5: LED ON command 8: LED1 to 4 ON EN = Low EN = High Send serial data "26H" 2: DIN1 to 4 dimming command 6: Dimming data (12mA) EN = Low EN = High Send serial data "4FH" 4: DIN5 dimming command F: Dimming data (150mA) EN = Low EN = High Send serial data "5AH" 5: LED ON command A: LED1 to 4 ON, LED5 ON EN = Low Example 3 input waveform SEIKO NPC CORPORATION —16 SM8134A TYPICAL APPLICATION CIRCUIT In circuits where the SM8134A logic-level inputs would become open circuit (floating) when the microcontroller supply stops, pull-down resistors should be connected to each logic-level signal input. C1 1.0µF C2 1.0µF C1M C1P C2M C2P 2.7 to 4.6V C4 4.7µF VIN VOUT Charge pump 1/ 1.5 C3 4.7µF Back Light Max 30mA Thermal shut down 4ch DIN1 Output voltage control DIN2 UVLO Current control & Current detect SCK SDA Microcontroller EN Control logic DIN3 DIN4 DIN5 Flash Max 150mA Pull down GND PGND Note. If the driving LEDs are less than 5 pcs, the unused DIN pins should be connected to GND. SEIKO NPC CORPORATION —17 SM8134A PERIPHERAL PARTS About the External Capacitors The best capacitors for use with the SM8134A are multi-layer ceramic capacitors. When selecting a multi-layer ceramic capacitor, only X5R and X7R dielectric types are strongly recommended, since the loss of capacitance in various conditions is less than other types such as Z5U and Y5V. The much loss of capacitance in various conditions may cause the output voltage unstable. Table. The EIA three digit "TC" code Lower temperature limit High temperature limit Maximum allowable capacitance change from + 25°C (0V DC) X = −55°C 5 = +85°C F = ± 7.5% Y = −30°C 6 = +105°C P = ± 10% Z = +10°C 7 = +125°C R = ± 15% 8 = +150°C S = ± 22% T = +22%/−33% U = +22%/−56% V = +22%/−82% For example : X5R About the Input Capacitor "C4" The parts layout of PCB may merely cause the “VOUT” output voltage unstable. In this case, increasing the “C4” input capacitance value or adding another capacitor on the VIN input line is effective to solve the unstable output voltage. FOOTPRINT PATTERN 3.6 ± 0.1 2.2 ± 0.1 0. 32 0.25 ± 0.05 0.7 ± 0.1 2.2 ± 0.1 0.5 × 3 = 1.5 ± 0.05 3.6 ± 0.1 0.5 × 3 = 1.5 ± 0.05 SEIKO NPC CORPORATION —18 SM8134A 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 SEIKO NPC CORPORATION (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. SEIKO NPC CORPORATION 15-6, Nihombashi-kabutocho, Chuo-ku, Tokyo 103-0026, Japan Telephone: +81-3-6667-6601 Facsimile: +81-3-6667-6611 http://www.npc.co.jp/ Email: [email protected] NC0417BE 2006.04 SEIKO NPC CORPORATION —19