SM8136A White LED Driver IC OVERVIEW The SM8136A is a charge pump type white LED driver. It can drive 1 to 3 backlight white LED connected in parallel, making it ideal for portable devices with small LCD. The charge pump switches between × 1 bypass mode to × 1.5 boost mode in response to LED drive current requirements. 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). Besides, the detection of switching is repeated in approx. 1sec-cycle by mode reset action, the SM8136A can respond to temporary variation of supply voltage. These ingenuities on switching detection can prolong the battery life to the fullest extent. Each LED drive current is controlled by a 3-channel LED drive current control circuit. ■ ■ ■ ■ ■ ■ ■ EN VOUT C1P PACKAGE DIMENSIONS (Unit: mm) Top view Bottom view 1.00 2.00 ± 0.07 0.40 × 2 = 0.80 ± 0.05 A 2.00 ± 0.07 B APPLICATIONS ■ ■ ■ ■ ■ ■ 12 8−C0.08 C0.30 1 0.60 0.10 S A B 0.10 S 0.70 ± 0.05 ■ 12 1 0.18 ± 0.05 φ0.05 M S A B 0.75 max ■ Cellular phone PDA Portable games Portable audio equipment Handy terminal Digital still camera Digital video camera LCD panel back light White LED driving 0.05 max ■ 1.00 ■ ■ NC GND VIN 0.25 ± 0.07 ■ 0.40 × 2 = 0.80 ± 0.05 ■ (Top view) DIN1 DIN2 DIN3 ■ Battery life extension by automatic charge pump switch between × 1 to × 1.5 according to the detection of the LED drive current Controlling 1 to 3 lights of white LED connected in parallel 1-wire input controlling ON/OFF and brightness control by signal controlling of EN pin Soft start circuit built-in Input voltage range No-load current (IOUT = 0mA): 2.7 to 4.6V Load current (IOUT = 60mA): 3.0 to 4.6V Maximum output voltage: 5.0V (typ) Maximum output current: 60mA (typ) Quiescent current Not-switching (× 1 mode): 0.3mA (typ) Switching (× 1.5 mode): 1.0mA (typ) Standby current: 0.01µA (typ) Operating frequency (boost mode): 1.0MHz (typ) LED drive current accuracy between channel: ± 5.0% Package: 12-pin QFN C1M C2M C2P ■ PINOUT 0.60 FEATURES S 0.05 S 0.40 ORDERING INFORMATION Device Package SM8136AB 12-pin QFN SEIKO NPC CORPORATION —1 SM8136A BLOCK DIAGRAM C1M C1P C2M C2P Charge pump 1/ 1.5 VIN VOUT Mode control & Output voltage control & Protection DIN1 Current control & Current detect DIN2 DIN3 Control logic EN NC GND (open at any time) PIN DESCRIPTION Number Name I/O Description 1 C1M – Charge pump boost capacitor connection 1M 2 C2M – Charge pump boost capacitor connection 2M 3 C2P – Charge pump boost capacitor connection 2P 4 C1P – Charge pump boost capacitor connection 1P 5 VOUT O LED drive voltage output 6 EN I Enable/LED drive current setting (High active) 7 DIN3 O LED drive current control output 3 (connect to ground when not used) 8 DIN2 O LED drive current control output 2 (connect to ground when not used) 9 DIN1 O LED drive current control output 1 (connect to ground when not used) 10 NC – No connection 11 PGND – Ground 12 VIN – Supply voltage input SEIKO NPC CORPORATION —2 SM8136A SPECIFICATIONS Absolute Maximum Ratings GND = 0V Parameter Symbol Rating Unit VIN voltage range VIN −0.3 to 6.0 V Input voltage range VEN –0.3 to VIN + 0.3 V VDIN1 to 3 –0.3 to VIN + 0.3 V VOUT 6.0 V IOUT 500 mA PD 800 (Ta = 25°C)*1 mW TJMAX +125 °C Tstg −55 to +125 °C Output voltage range VOUT output current Power dissipation Junction temperature Storage ambient temperature range *1. When mounted on a 4-layer board. Note. The device may suffer breakdown if any one of these parameter ratings is exceeded. Power dissipation [mW] 1000 800 600 400 200 0 25 35 45 55 65 Operating temperature [°C] 75 85 Package power dissipation when mounted on 4-layer board Recommended Operating Conditions GND = 0V Rating Parameter Supply voltage range Pin VIN Symbol Conditions Unit min typ max VIN0 IOUT = 0mA 2.7 3.6 4.6 V VIN IOUT = 60mA 3.3 3.6 4.6 V Logic-level inputs 0 − VIN V −40 − +85 °C Input voltage range EN VES Ambient temperature range − Ta SEIKO NPC CORPORATION —3 SM8136A Electrical Characteristics VIN = 3.6V, GND = 0V, Ta = 25°C unless otherwise noted. Rating Parameter Standby current Pin VIN Quiescent current 1 VIN Quiescent current 2 Output voltage VOUT Symbol Condition Unit min typ max ISTB Standby mode – 0.01 1.00 µA IDD1 ×1.0 mode, IOUT = 0mA – 0.3 1.0 mA IDD2 ×1.5 mode, IOUT = 0mA – 1.0 2.0 mA ×1.5 mode, VIN = 3.6V, IOUT = 0mA 4.5 5.0 5.5 V ×1.5 mode, VIN = 3.0V, IOUT = 60mA – 3.5 – V VOUT Maximum output current VOUT IOUT ×1.5 mode 60 – – mA Operating frequency C1M fOSC ×1.5 mode switching frequency 800 1000 1200 kHz EN TPOR Rest time from when power is applied – 0.05 1.00 ms Power-ON rise time EN, VIN TPR EN = VIN, time from 0.3V to 2.7V – – 50 µs Soft start time DIN1 to 3 TSS EN startup → ILED rising edge – 2.00 3.00 ms LED drive pin leakage current DIN1 to 3 ILeak1 to 3 Standby mode, DIN pin = 5.0V – 0.01 1.00 µA LED drive current DIN1 to 3 ILED1 to 3 ×1.0 mode (3-channel average value) 18.0 20.0 22.0 mA LED drive current accuracy DIN1 to 3 ∆ILED ×1.0 mode, relative accuracy between channels at ILED maximum settings –5.0 – +5.0 % LED drive pin voltage DIN1 to 3 VDIN1 to 3 ×1.0 mode, ILED = 20mA – 120 – mV ×1.0 ↔ ×1.5 mode switching threshold voltage VIN VTH1.0 to 1.5 VF (LED) = 3.3V, ILED = 20mA – 3.46 – V EN hold time*1*2 EN TCEH Time from when EN = LOW until shutdown 0.50 1.00 1.50 ms EN HIGH-level input time*1 EN TENH EN input pulse HIGH-level minimum pulsewidth 4.0 – – µs EN LOW-level input time*1*2 EN TENL EN input pulse LOW-level pulsewidth range 4.0 – 500 µs 1.4 – – V EN VIH HIGH-level input voltage range Logic input voltage VIL LOW-level input voltage range – – 0.3 V IIH Pull-down pin, EN pin = 3.6V – 5.0 10.0 µA IIL EN pin = 0V –1.0 – – µA Internal power-ON reset time*1 Logic input current EN *1. Design guaranteed value *2. When shutdown EN When dimming > 1.5msec 4µsec to 500µsec EN SEIKO NPC CORPORATION —4 SM8136A FUNCTIONAL DESCRIPTION LED Drive Current Setting The SM8136A LED drive current can be set using the EN pin. The EN input is used to enable/disable circuit operation. It also is used by a built-in counter that counts the number of input pulses in order to set the LED current value. The built-in counter is a 4-bit counter for 16-step adjustment (DATA = 1 to 16). On the 16th pulse (DATA = 16), the LED current drive circuit shuts down and LED current is zero. On the 17th pulse (DATA = 1), the current returns to the maximum value. As the initial pulse (DATA = 1) sets the current to the maximum value, the device can also be used in applications that do not support pulsed input. Table 1. EN input pulse count and LED current setting values DATA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 EN pulse count 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 20.00 18.7 17.3 16.0 14.7 13.3 12.0 10.7 9.3 8.0 6.7 5.3 4.0 2.7 1.3 0 ILED [mA] EN Input Signal and LED Current Setting (Initialization) On the first rising edge of EN, the internal startup signal goes HIGH and LED current will start to flow after the soft start time has elapsed. As the LED current setting is adjusted by counting the number of input pulses on EN, the EN input voltage must be switched HIGH → LOW → HIGH repeatedly to set the current to a lower value. After the desired value is achieved, the EN input voltage is held HIGH to maintain the LED current setting. If the EN input goes LOW, the LED current does not flow. The EN data input circuit operates even though the LED current does not flow during the soft start interval, but as long as the current value is set during the soft start interval the LED drive circuits will start to drive the LEDs with that constant current setting. However, note that the setting is valid only after the power-ON reset when the VIN supply is applied. Accordingly, allow 1ms or more after connecting the VIN supply before setting the current value using the EN input. 1 3 2 5 4 7 6 8 EN input signal 1 2 3 4 5 ILED1-3 6 7 8 EN input signal and LED current setting ■ LED current setting is determined by the number of EN input signal rising edges. Furthermore, no LED current flows until the soft start time has elapsed. SEIKO NPC CORPORATION —5 SM8136A VOUT Output Circuit Mode Switching The SM8136A output mode switches between 3 operating modes in response to the operating conditions. The modes are: standby mode, ×1.0 mode (VIN through mode), and ×1.5 mode (1.5-times charge pump boost). The VOUT output switches automatically between these modes in response to the drive LED characteristics and the overall power consumption. Switching from ×1.0 mode to ×1.5 mode is controlled automatically by an internal circuit. The operating mode cannot be specified by an external control signal. Startup: Internal Reset Time and Soft Start Time The SM8136A normal startup procedure (after VIN has been applied previously) is to switch from standby mode to the ×1.0/×1.5 operating modes when the EN enable input goes HIGH. The soft start time (described on the following page) begins after switching to the operating mode using EN. VIN VIN High (1) Soft start time EN Standby mode ENABLE ON (2) Normal startup (1) VIN is HIGH, EN is LOW (standby mode) (2) Switches to an operating mode when EN goes HIGH (soft start time begins) If the use at EN = VIN when power is applied, the startup commences after the power-ON reset (POR) time (approximately 50µs) has elapsed. < 50µs EN = VIN (1) 2.7V 0.3V Internal power on reset Internal enable (CE) (2) POR time typ: 50µs Soft start time (3) Standby mode 1.5 mode Internal reset operation when power is applied (power-ON reset) (1) When using at EN = VIN, rising time from 0.3V to 2.7V should set < 50µs. (2) Power-ON reset (POR) circuit resets internal circuits approximately 50µs after the power is applied. (3) If EN is HIGH when power is applied, the internal circuits start operating when the internal “CE” signal rising edge occurs after the power-ON reset time. If EN is LOW when power is applied, the “CE” rising edge occurs simultaneously with the first rising edge. SEIKO NPC CORPORATION —6 SM8136A Immediately after startup, the device operates in ×1.5 mode for a fixed interval (soft start time: approximately 2ms) to set the current for LEDs connected to the DIN pins. VIN High VIN EN (1) Dimming pulse enable Soft start time typ: 2ms LED current LED ON (2) Soft start time and LED current (1) If the EN signal is input after power is applied, the soft start time begins on the EN rising edge. The EN input signal for dimming is active during the soft start time. (2) The LED drive starts immediately before the end of the LED turn-on delay time. Switching to Standby Mode The SM8136A operating mode switches from ×1.0/×1.5 mode to standby mode if EN goes LOW and stays LOW for an interval of 1.00ms (typ). This function is used to switch the internal circuits to standby mode automatically when the LEDs turn OFF in order to reduce current consumption. EN CE hold time typ: 1.00ms LED current 1.0 or 1.5 Standby mode Switching to standby mode, and EN hold time ■ When EN is LOW for longer than the CE hold time of 1.00ms (typ), the SM8136A switches to standby mode. In standby mode, the internal circuits are reset, hence the drive current settings must be re-entered to restart the device. SEIKO NPC CORPORATION —7 SM8136A Switching from ×1.0 Mode to ×1.5 Mode When the LEDs are ON and can be driven at the fixed current value set by the EN pulse input without needing to boost the VIN input voltage, the VOUT output operates in ×1.0 mode. In other words, if sufficient current flows to counter the LED forward-bias voltage drop VF, it means the VOUT voltage may drop below 5.0V. The longer that the driver output operates in the more efficient ×1.0 mode, the lower the total power consumption and the longer the battery life can be extended. Also, by using LEDs with low VF and a lower LED drive current setting, the longer the device can operate automatically in ×1.0 mode. 1.0 mode (high efficiency) 1.5 mode (low efficiency) High VF LED 1.0 mode (high efficiency) 1.5 mode (low efficiency) Low VF LED High VIN Low VOUT mode switching interval comparison due to drive LED “VF” variation If the VIN voltage drops and the LED current drops below the fixed current setting in ×1.0 mode, an undercurrent detection circuit connected to each LED drive circuit activates and automatically switches the VOUT output mode to ×1.5 mode that uses a charge pump to boost the voltage by a factor of 1.5. The LED undercurrent detection circuit switches the output mode when it detects an undercurrent condition on any one of the three channels. Accordingly, there should be as low a variation as possible in drive LED VF values in order to improve overall efficiency. VIN voltage 1.0 (1) 1.5 threshold Lack of LED current detect ILED detector (2) 1.5 mode VOUT mode (3) 1.0 mode 5.0V VOUT voltage (4) VIN voltage drop and VOUT output voltage (1) The VIN voltage drops below the ×1.5 mode threshold value. (2) When the voltage drops below the ×1.5 mode threshold, the ILED detection circuit raises an ILED undercurrent signal. (3) The VOUT output switches to ×1.5 mode in response to the ILED undercurrent signal. (4) The VOUT voltage drops below 5.0V but still supplies sufficient current until reaching the ×1.5 switching threshold. Note that if the LEDs connected to the DIN pins are switched after startup, the LED connection detection circuit will operate incorrectly and the correct mode switching functions cannot occur. SEIKO NPC CORPORATION —8 SM8136A Switching from ×1.5 Mode to ×1.0 Mode The LED 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 or more 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 SM8136A outputs a mode reset signal once every 1.0 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. Mode reset VOUT mode (1) 1.0sec/cycle 1.5 mode 1.5 mode (2) 1.0 mode Mode hold L: hold min 80µs max 200µs (3) ILED detector ignore 5.0V VOUT voltage (4) ILED detector Switching from ×1.5 mode to ×1.0 mode due to mode reset signal (1) Mode reset signal is output once every 1.0 seconds. (2) Mode switches from ×1.5 to ×1.0 mode on the rising edge of the mode reset signal. (3) A 200µs (max) mode hold time begins after switching to ×1.0 mode. LED drive current insufficient state is detected but the mode is not switched during this interval. (4) LED drive current insufficient signal is ignored during the mode hold time, but normal mode switching operation resumes when the mode hold time elapses. SEIKO NPC CORPORATION —9 SM8136A A mode hold signal of 200µs (max) duration is output immediately after switching to ×1.0 mode. The VOUT output is held in ×1.0 mode and any LED drive current insufficient detection signal is ignored during the mode hold signal output. For example, if the VIN voltage drops and the VOUT output voltage in ×1.0 mode cannot provide sufficient current to drive the LEDs, a LED drive current insufficient condition occurs momentarily due to the mode reset. The LED low-current detector circuit outputs a LED drive current insufficient signal immediately after switching modes, but during the mode hold time the device stays in ×1.0 mode and does not switch to ×1.5 mode. Consequently, the VOUT voltage drops and the LED brightness decreases during the 85µs (min) to 200µs (max) mode hold time. However, a 200µs decrease in the brightness is not a problem as it is not perceptible to the human eye. 1.0 1.5 threshold VIN voltage 1.0sec Mode reset (1 sec/cycle) Mode hold (L: hold) max 200µS VOUT mode (H: 1.5, L: 1.0) 5.0V VOUT voltage Low ILED detector (H: Low ILED) VOUT drop due to mode reset signal SEIKO NPC CORPORATION —10 SM8136A PERIPHERAL PARTS About the External Capacitors The best capacitors for use with the SM8136A 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. 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 Recommended parts list Dimensions [mm] Manufacture Part number Capacitance [µF] W L T TDK C1608JB1C105K 1.0 1.6 0.8 0.8 MURATA GRM188B11A105KA61 1.0 1.6 0.8 0.8 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. SEIKO NPC CORPORATION —11 SM8136A TYPICAL APPLICATION CIRCUITS LED × 3 1µF C1M VIN 1µF C1P 1µF C2M C2P VOUT Charge pump 1/ 1.5 1µF Mode control & Output voltage control & Protection 20mA 3 DIN1 Current control & Current detect DIN2 DIN3 EN Control logic GND Note. If the driving LED is less than 3 pcs, unused DIN pins should be connect to GND. The HIGH-level and LOW-level pulsewidths for the pulse input on EN must be 4.0µs or longer (see “Electrical Characteristics”). SEIKO NPC CORPORATION —12 SM8136A LED × 2 1µF C1M VIN 1µF C1P 1µF C2M C2P VOUT Charge pump 1/ 1.5 1µF Mode control & Output voltage control & Protection 20mA 2 DIN1 Current control & Current detect DIN2 DIN3 EN Control logic GND Note. If the driving LED is less than 3 pcs, unused DIN pins should be connect to GND. The HIGH-level and LOW-level pulsewidths for the pulse input on EN must be 4.0µs or longer (see “Electrical Characteristics”). SEIKO NPC CORPORATION —13 SM8136A 0.18 ± 0.05 1.0 0.6 ± 0.1 φ 0.30 Thermal Via 2.6 ± 0.1 1.4 ± 0.1 0.4 2=0.80 ± 0.05 1.4 ± 0.1 2.6 ± 0.1 0.4 2=0.80 ± 0.05 FOOTPRINT PATTERN 1.0 SEIKO NPC CORPORATION —14 SM8136A 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] NC0717AE 2008.12 SEIKO NPC CORPORATION —15