SM8132A White LED Driver IC OVERVIEW The SM8132A is a charge pump DC/DC converter that switches between ×1 and ×1.5 automatically. The SM8132A switches between ×1 and ×1.5 according to detected LED drive current, so that the battery life can be prolonged to the fullest extent. Since the connected LED are all detected for the switching, the SM8132A can respond to the variation of LED forward voltage. 4-channel of LED drive current control circuit is built-in, the SM8132A can control 1 to 4 lights of white LED, which are connected in parallel. The LED drive current per channel is set up by external resistor. Besides, the input signal controlling of EN pin allows ON/OFF and dimming. FEATURES ■ ■ ■ ■ ■ ■ ■ Battery life extension by automatic charge pump switch between ×1 and ×1.5 according to the detection of the LED drive current Controlling 1 to 4 lights of white LED connected in parallel Set up LED drive current value by external resistor (5kΩ:5mA/ch, 15kΩ:15mA/ch, 20kΩ:20mA/ch) 1-wire input controlling ON/OFF and brightness control by input signal controlling of EN pin Soft start circuit built-in Thermal shut down circuit built-in ■ ■ ■ ■ ■ ■ ■ ■ Supply voltage range • No-load current (IOUT = 0mA): 2.7 to 4.6V • Load current (IOUT = 80mA): 3.3 to 4.6V Maximum output voltage: 4.2V (typ) Maximum output current: 80mA (typ) Quiescent current • Not-switching (×1 mode): 0.3mA (typ) • Switching (×1.5 mode): 1.0mA (typ) Standby current (Power save mode): 0.01µA (typ) Operating frequency (×1.5 mode): 750kHz (typ) LED drive current matching (RSET = 20kΩ): ± 3% Package: 16-pin QFN WL-CSP (under development) APPLICATIONS ■ ■ ■ ■ ■ ■ ■ ■ Cellular phone PDA Portable games Handy terminal Digital still camera Digital video camera LCD back light White LED driving ORDERING INFORMATION Device Package SM8132AB 16-pin QFN SM8132AW WL-CSP NIPPON PRECISION CIRCUITS INC.—1 SM8132A PACKAGE DIMENSIONS (Unit: mm) QFN-16 TOP VIEW 3.0 ± 0.08 BOTTOM VIEW 1.8 1.8 0.3 ± 0.1 0.5 3.0 ± 0.08 A 3 = 1.5 ± 0.05 B C 0.3 φ 0.05 M S A B 0.05 S 0.5 0.7 ± 0.05 0.2 S 0.2 ± 0.05 S 0.1 ± 0.05 0.02 S A B 0.22 ± 0.05 WL-CSP (under development) TBD NIPPON PRECISION CIRCUITS INC.—2 SM8132A PINOUT (Top view) WL-CSP (under development) GND ISET DIN3 NC QFN-16 EN DIN4 NC VIN TBD PGND VOUT C2M C2P DIN2 DIN1 C1P C1M PIN DESCRIPTION Number Name I/O – PGND – Charge pump ground connection 2 – VOUT O LED drive voltage output 3 – C2M – Charge pump capacitor connection 2M 4 – C2P – Charge pump capacitor connection 2P 5 – VIN – Voltage supply 6 – NC – No connection 7 – DIN4 O LED drive current control output 4 (connect to ground when not used) QFN-16 WL-CSP 1 Description 8 – EN Ip*1 9 – NC – No connection 10 – DIN3 O LED drive current control output 3 (connect to ground when not used) 11 – ISET I LED drive current setting resistor connection 12 – GND – Ground 13 – DIN2 O LED drive current control output 2 (connect to ground when not used) 14 – DIN1 O LED drive current control output 1 (connect to ground when not used) 15 – C1P – Charge pump capacitor connection 1P 16 – C1M – Charge pump capacitor connection 1M Enable data input (High active) *1. Ip: Input with built-in pull-down resistor NIPPON PRECISION CIRCUITS INC.—3 SM8132A BLOCK DIAGRAM C1M C1P C2M C2P Charge pump 1 /1.5 VIN VOUT DIN1 Mode control & Output voltage control & Protection DIN2 Current control & Current detect TSD DIN3 DIN4 EN Control logic ISET GND PGND NIPPON PRECISION CIRCUITS INC.—4 SM8132A SPECIFICATIONS Absolute Maximum Ratings GND = 0V Parameter Symbol Rating Unit VIN voltage range VIN −0.3 to 5.5 V Input voltage range VEN VGND – 0.3 to VIN + 0.3 V VDIN1 to 4 VGND – 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 Output voltage range VOUT output current Power dissipation Junction temperature Storage temperature range *1. When mounted on a 4-layer PCB. Note. The device may suffer breakdown if any one of these parameter ratings is exceeded. 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 = 0V Rating Parameter Supply voltage range Pin VIN Symbol Conditions Unit min typ max VIN0 ×1.0 mode, IOUT = 0mA 2.7 3.6 4.6 V VIN ×1.5 mode, IOUT = 80mA 3.3 3.6 4.6 V Each logic-level pin 0 − VIN V −30 − +85 °C Input voltage range EN VES Ambient temperature range − Ta NIPPON PRECISION CIRCUITS INC.—5 SM8132A Electrical Characteristics VIN = 3.6V, GND = 0V, Ta = 25°C unless otherwise noted. Rating Parameter Pin Standby current VIN Quiescent current VIN Symbol Condition Unit min typ max ISTB Power-save 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 3.0 mA Output voltage VOUT VOUT ×1.5 mode, IOUT = 80mA 4.0 4.2 4.4 V Maximum output current VOUT IOUT ×1.5 mode 80 – – mA Operating frequency C1M fOSC ×1.5 mode switching frequency 650 750 850 kHz EN TPOR Time from when power is applied until internal circuits reset – 0.05 1.00 ms Soft start time DIN1 to 4 TSS EN startup → ILED rising edge – 1.3 5.0 ms LED drive pin leakage current DIN1 to 4 Ileak1 to 4 Power-save mode, DIN pin = 4.2V – 0.01 1.00 µA LED drive current DIN1 to 4 ILED1 to 4 ×1.0 mode, RSET = 20kΩ 19.0 20.0 21.0 mA LED drive current matching DIN1 to 4 ∆ILED ×1.0 mode, matching between channels with ILED maximum setting –3.0 – +3.0 % LED drive pin voltage DIN1 to 4 VDIN1 to 4 ×1.0 mode, RSET = 20kΩ – 160 – mV ISET RSET RSET maximum value – – 50 kΩ Input signal frequency*1 EN fENIN EN input pulse duty 50%, maximum signal input frequency – – 150 kHz Input pulse width*1 TENH Minimum EN pulse HIGH-level width 3.0 – – EN µs TENL Minimum EN pulse LOW-level width 3.0 – – µs TCEH Time from when EN = LOW until LED drive circuit shutdown 1.17 1.37 1.63 ms VIH HIGH-level input voltage range 1.8 – – V VIL LOW-level input voltage range – – 0.6 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 LED drive current setting resistance*1 Hold time EN Input voltage EN Input current EN *1. Design guaranteed value NIPPON PRECISION CIRCUITS INC.—6 SM8132A VOUT Efficiency 100 VOUT efficiency [%] 90 80 VF = 3.2V 70 VF = 3.4V VF = 3.6V 60 50 3.2 VF = 3.8V 3.4 3.6 3.8 4.0 VIN [V] 4.2 4.4 4.6 4.4 4.6 Efficiency of PIN vs. POUT (LED × 4pcs, ILED = 20mA, IOUT = 80mA) 100 VOUT efficiency [%] 90 80 VF = 3.2V 70 VF = 3.4V VF = 3.6V 60 50 3.2 VF = 3.8V 3.4 3.6 3.8 4.0 VIN [V] 4.2 Efficiency of PIN vs. POUT (LED × 3pcs, ILED = 15mA, IOUT = 45mA) NIPPON PRECISION CIRCUITS INC.—7 SM8132A FUNCTIONAL DESCRIPTION LED Drive Current Setting The SM8132A LED drive current setting is controlled by the combination of resistance connected to ISET and the EN input signals. (1) Setting LED Drive Current using RSET The maximum drive current per LED (when DATA = 1) is determined by the external resistance connected to ISET. For example, if ILED MAX = 15mA, from the graph below, a resistance “RSET” of 15kΩ should be connected between ISET and GND. Note that while RSET can have a maximum resistance 50kΩ, the total LED output current must not exceed the maximum output current of 80mA. 50 ISET ILED [mA] 40 RSET 30 20 10 0 0 GND 10 20 30 40 50 RSET [kΩ] LED drive current maximum setting using RSET (2) Setting LED Drive Current using EN Input Signals The EN input ENABLE/DISABLE circuit, also simultaneously counts the number of input pulses using an internal counter and adjusts the LED drive current setting in response. The internal 4-bit counter provides 16step (DATA = 1 to 16) adjustment, where each step is 1/15th of the maximum current (ILED MAX) set by RSET. On the 16th pulse (DATA = 16), the LED drive current control circuit shuts down. On the 17th pulse (DATA = 1), the LED drive current is reset to the maximum current value. As the current is set to the maximum value on the first pulse, applications without pulse input can also be employed (by controlling brightness using RSET). RSET=10kΩ RSET=15kΩ RSET=20kΩ EN 25 123 ILED [mA] 20 EN input pulse 15 10 5 0 0 GND 4 8 12 16 DATA set by EN input pulse LED drive current setting variation using EN input pulse modulation Table. LED drive current setting and EN input pulse count DATA EN pulse count ILED 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 15/15 14/15 13/15 12/15 11/15 10/15 9/15 8/15 7/15 6/15 5/15 4/15 3/15 2/15 1/15 0 NIPPON PRECISION CIRCUITS INC.—8 SM8132A EN input signal and LED drive current setting (startup) An internal startup signal goes HIGH on the first rising edge of EN, and LED drive current starts after the softstart time expires. The LED drive current control circuit sets the current by counting the input pulses on EN, hence the EN input voltage must be switched HIGH → LOW → HIGH the required number of data steps to reduce the current setting. When the desired setting is reached, the EN input voltage should be tied HIGH to maintain the setting. Note that the LED drive current does not flow when EN is LOW. The EN data input circuit operates during the soft-start time when no LED drive current flows, hence the current setting can be adjusted during the soft-start time and the LED drive circuit will then start at the desired current setting. However, setting the current using EN signal pulses is possible only when the power-ON reset ends after a rising edge on the VIN supply. Consequently, a delay of 1ms or greater should be allowed after VIN is applied before starting the EN input signals. EN input signal ILED 1 to 4 1 1 2 2 3 4 3 5 4 6 5 7 6 8 7 8 EN input signal and LED drive current setting ■ The LED drive current is set by the number of EN input signal rising-edge. The LED drive current control circuit is disabled, and the LED drive current does not flow during EN input signal LOW interval or at startup until after the soft-start time expires. EN input signal and LED drive current setting (disable interval) The LED drive current setting due to EN input is set by the 4-bit counter (16 steps). On the 17th pulse, the counter DATA = 1 and the current is reset to the maximum current value. When the counter DATA = 16, ILED = 0mA and the LED drive circuit shuts down. EN input 11 12 13 14 15 16 17 18 19 20 21 ILED disable signal ILED off 1 ILED 1 to 4 11 12 13 14 2 3 4 5 15 16 LED drive current setting disable interval When EN is held LOW for an extended interval, the internal enable signal “CE” goes LOW and the device enters power-save mode. In this mode, the EN input internal counter is reset and subsequent rising-edge pulses on EN restart the counter from DATA = 1. NIPPON PRECISION CIRCUITS INC.—9 SM8132A VOUT Output Circuit Mode Switching The SM8132A switches between 3 output states: power-save 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. Power-ON internal reset time The SM8132A switches from standby condition (power-save mode) to normal operating condition (×1.0/×1.5 mode) on the first rising edge of EN. Note that if the VIN supply voltage is applied when EN is HIGH, startup occurs after the internal power-ON reset time (approximately 50µs) expires. At startup, operation commences in ×1.5 mode for a fixed interval during the soft-start time in order to determine whether a LED is connected to each DIN pin. VIN power source (1) VIN Power on reset output POR time typ: 50µs (2) Soft start time Internal enable (CE) (3) Power save mode 1.5 mode Power-ON reset operation (1) VIN voltage rises when power is applied. (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. EN input signal LED current EN (1) Dimming pulses enable Soft start time typ: 1.3ms LED ON (2) Soft start time and LED current (1) If the EN signals are input after POR time is expired, the soft start time begin from the first EN input rising edge. The current setting can be adjusted during the soft-start time. (2) LED current starts flow immediately before the soft start time expires. NIPPON PRECISION CIRCUITS INC.—10 SM8132A Switching to power-save mode The internal circuit operating mode switches from ×1.0/×1.5 mode to power-save mode when EN goes LOW and do not switch HIGH for an interval of 1.63ms (max). This function turns the LEDs OFF and automatically transfers internal circuit control to power-save mode, suppressing current consumption. EN Internal enable (CE) Power save 1.0 or 1.5 CE hold time 1.63ms (max) Power save EN input signal and internal enable signal “CE” ■ If the EN input signal is held for an interval greater than the “CE” hold time 1.63ms (max), the SM8132A switches to power-save mode. The internal circuits are reset on the “CE” falling edge, and the current setting must be re-established before restart. Switching from ×1.0 mode to ×1.5 mode If the LEDs can be driven solely by the current determined by RSET and EN pulse input 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 4.2V. 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 RSET 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 4-channel LED drive circuits, thus it is recommended that LEDs have small “VF” variation to optimize the total efficiency. NIPPON PRECISION CIRCUITS INC.—11 SM8132A VIN input voltage 1.0 Low ILED detector 1.5 threshold (1) Low ILED detected VOUT mode (2) 1.0 mode 1.5 mode 4.2V 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 4.2V 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. NIPPON PRECISION CIRCUITS INC.—12 SM8132A 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 SM8132A 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 4.2V (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. NIPPON PRECISION CIRCUITS INC.—13 SM8132A 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) 4.2V VOUT output voltage Low ILED detector (H: low ILED) VOUT drop due to the mode reset single NIPPON PRECISION CIRCUITS INC.—14 SM8132A PERIPHERAL PARTS About the External Capacitors The best capacitors for use with the SM8132A 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. About the LED Current Setting Resistor "RSET" The LED drive current variation depends on the LED drive current setting resistor “RSET” variation. Therefore, a precise resistor is recommended for RSET. The ISET output current value is about 20µA, so a 1/10 watt class resistor is acceptable as the RSET. NIPPON PRECISION CIRCUITS INC.—15 SM8132A TYPICAL APPLICATION CIRCUITS C1 = 1µF C1M C1P 2.8 to 4.3V VIN C2 = 1µF C2M C2P VOUT Charge pump 1 /1.5 C4 = 4.7µF C3 = 4.7µF 20mA 4 DIN1 Mode control & Output voltage control & Protection DIN2 Current control & Current detect TSD DIN3 DIN4 EN Control logic ISET RSET = 20kΩ GND PGND ILED MAX = 20mA circuit example Note. If the driving LED is less than 4 pcs, unused DIN pins should be connect to GND. NIPPON PRECISION CIRCUITS INC.—16 SM8132A 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 NIPPON PRECISION CIRCUITS INC.—17 SM8132A 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. 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] NC0411AE 2005.05 NIPPON PRECISION CIRCUITS INC.—18