SM8135B NPC | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 19
Technical content
SEIKO NPC CORPORATION —1 White LED Driver IC OVERVIEW The SM8135B is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in parallel, making it ideal for portable devices with small LCD. The charge pump switches between 1 bypass mode, 1.5 and 2 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 volt- age drop (VF). Besides, the detection of switching is repeated in approx. 1sec-cycle by mode reset action, the SM8135B 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 4-channel LED drive current control circuit. The LED drive current per channel is setup by external resistor.
FEATURES
I Battery life extension by automatic charge pump switch between 1.5 and 2 according to the detection of the LED drive current I Controlling 1 to 4 lights of white LED connected in parallel I Set up LED drive current value by external resistor (120k Ω : 20mA/ch) I 1-wire input controlling I ON/OFF and brightness control by signal control- ling of EN pin I Soft start circuit built-in I Thermal shut down circuit built-in I Input voltage range No-load current (I OUT = 0mA): 2.7 to 4.6V Load current (I OUT = 80mA): 3.0 to 4.6V I Maximum output voltage: 4.9V (typ) I Maximum output current: 80mA (typ) I Quiescent current Not-switching ( 1 mode): 0.3mA (typ) Switching ( 1.5 mode): 1.5mA (typ) Switching ( 2 mode): 1.5mA (typ) I Standby current: 0.01 µ A (typ) I Operating frequency (boost mode): 1MHz (typ) I LED drive current accuracy between channel (REST = 120k Ω ): ± 5% (max) I Package: 16-pin QFN
APPLICATIONS
I Cellular phone I PDA I Portable games I Handy terminal I Digital still camera I Digital video camera I LCD panel back light I White LED driving PINOUT (Top view) PACKAGE DIMENSIONS (Unit: mm)
ORDERING INFORMATION
3.0 ± 0.08 3.0 ± 0.08 0.22 ± 0.05 0.3 ± 0.1 C 0.3 1.8 1.8 φ 0.05 M 0.5 3 = 1.5 ± 0.05 S
0.02 S AB
0.5 BSA 0.2 S S0.05 0.1 ± 0.05 0.2 ± 0.05 0.7 ± 0.05 A B
SEIKO NPC CORPORATION —2 BLOCK DIAGRAM PIN DESCRIPTION Number Name I/O Description
1 C2M – Charge pump boost capacitor connection 2M
2 PGND – Charge pump ground
3 C1P – Charge pump boost capacitor connection 1P
4 C1M – Charge pump boost capacitor connection 1M
5 VIN – Supply voltage input
6 GND – Ground
7 EN I Enable/LED drive current setting (High active)
8 ISET I LED drive current setting resistor connection
9 DIN4 O LED drive current control output 4
connect to ground when not used)
10 DIN3 O LED drive current control output 3
connect to ground when not used)
11 NC – No connection (leave open circuit for normal operation)
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 VOUT O LED drive voltage output
16 C2P – Charge pump boost capacitor connection 2P
(open at any time) 1/ 1.5/ 2 PGND
SEIKO NPC CORPORATION —3 SPECIFICATIONS Absolute Maximum Ratings GND = 0V Note. The device may suffer breakdown if any one of these parameter ratings is exceeded. Recommended Operating Conditions GND = 0V Parameter Symbol Rating Unit VIN voltage range V IN 0.3 to 5.5 V Input voltage range V EN –0.3 to V IN + 0.3 V Output voltage range V DIN1 to 4 –0.3 to V IN + 0.3 V V OUT 5.5 V VOUT output current I OUT 500 mA Power dissipation P D 800 Ta = 25 *1. When mounted on a 4-layer PCB. mW Junction temperature T JMAX +125 C Storage ambient temperature range T stg 55 to +125 C Package power dissipation when mounted on 4-layer board Parameter Pin Symbol Conditions Rating Unit min typ max Supply voltage range VIN V IN0 I OUT = 0mA 2.7 3.6 4.6 V V IN I OUT = 80mA 3.3 3.6 4.6 V Input voltage range EN V ES Logic-level pin 0 V IN V Ambient temperature range Ta +85 C 200 400 600 800 1000 25 35 45 55 65 75 85 Operating temperature [°C] Power dissipation [mW]
SEIKO NPC CORPORATION —4
Electrical Characteristics
V IN = 3.6V , GND = 0V , Ta = 25 C unless otherwise noted. Parameter Pin Symbol Condition Rating Unit min typ max Standby current VIN I STB Standby mode – 0.01 1.00 µ A Quiescent current 1 VIN I DD1 1.0 mode, I OUT = 0mA – 0.3 1.0 mA Quiescent current 2 *1. Design guaranteed value I DD2 1.5 mode, I OUT = 0mA – 1.5 4.5 mA Quiescent current 3 I DD3 2.0 mode, I OUT = 0mA – 1.5 4.5 mA Output voltage VOUT V OUT 4.4 4.9 5.4 V Maximum output current VOUT I OUT 1.5/ 2.0 mode 80 – – mA Operating frequency C1M f OSC 1.5/ 2.0 mode switching frequency 750 1000 1250 kHz Internal power-ON reset time EN T POR Rest time from when power is applied – 0.05 1.00 ms Soft start time DIN1 to 4 T SS EN startup I LED rising edge 0.70 1.43 3.00 ms LED drive pin leakage current DIN1 to 4 I Leak1 to 4 Standby mode, DIN pin = 4.9V – 0.01 1.00 µ A LED drive current DIN1 to 4 I LED1 to 4 1.0 mode 18.0 20.0 22.0 mA LED drive current matching DIN1 to 4 I LED 1.0 mode, relative accuracy between channels at I LED maximum setting –5.0 – +5.0 % LED drive pin voltage DIN1 to 4 V DIN1 to 4 1.0 mode – 200 – mV LED drive current setting resistance ISET RSET RSET minimum value 60 – – k Ω EN hold time *1*2 *2. EN T CEH Time from when EN = LOW until shutdown 0.50 1.00 1.50 ms EN HIGH-level input time EN T ENH EN input pulse HIGH-level minimum pulsewidth 3.0 – – µ s EN LOW-level input time *1*2 EN T ENL EN input pulse LOW-level pulsewidth range 3.0 – 500 µ s Logic input voltage EN V IH HIGH-level input voltage range 1.4 – – V V IL LOW-level input voltage range – – 0.3 V Logic input current EN I IH Pull-down pin EN pin = 3.6V – 5.0 10.0 µ A I IL EN pin = 0V –1.0 – – µ A EN When shutdown > 1.5msec EN When dimming 3µsec to 500µsec
SEIKO NPC CORPORATION —5 FUNCTIONAL DESCRIPTION LED Drive Current Setting The SM8135B LED drive current can be set using a combination of 2 methods: (1) current setting resistance connected to ISET, and (2) input pulse control on the EN pin. (1) Setting LED drive current using RSET The LED drive maximum current value per LED (I LED MAX) is determined by the resistor (RSET) connected to the ISET pin. The relationship between RSET and ILED MAX is given by the following equation. ILED MAX [mA] = 2400/RSET [kΩ] (For example, ILED MAX = 20mA when RSET = 120kΩ.) The RSET resistance has a minimum rating of 60kΩ. At this value of resistance, the ILED MAX has a maximum rating of 40mA/LED. However, note that the total LED drive current for all LEDs must not exceed 80mA. ISET RSET GND RSET vs. ILED MAX 0 100 RSET [kΩ] 200 300 400 500 ILED MAX [mA]
(refer to section “(1) Setting LED drive current using RSET”). Table 1. EN input pulse count and ILED relationship (ILED MAX = 20mA)
SEIKO NPC CORPORATION —7 VOUT Output Circuit Mode Switching The SM8135B output mode switches between 4 operating modes in response to the operating conditions. The modes are: standby mode, ×1.0 mode (VIN through mode), ×1.5 mode (1.5-times charge pump boost), and allows the VOUT output to be adjusted automatically to match drive LED characteristics. Switching between ×1.0 mode, ×1.5 mode, and ×2.0 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 SM8135B normal startup procedure (after VIN has been applied previously) is to switch from standby mode to the ×1.0/×1.5/×2.0 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. (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 VIN supply voltage is applied when EN is HIGH level, startup commences after the power-ON reset (POR) time (approximately 50µs) has elapsed. (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 ris- ing 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. Normal startup Internal reset operation when power is applied (power-ON reset) Soft start time VIN EN VIN High ENABLE ON (1) (2)Standby mode VIN power source 1.5 mode Internal power on reset Internal enable (CE) POR time typ: 50µs (1) (2) (3) Soft start time Standby mode
SEIKO NPC CORPORATION —8 Immediately after startup, the device operates in ×1.5 mode for a fixed interval (soft start time: approximately 1.43ms) to set the current for LEDs connected to the DIN pins. After the soft start time has elapsed, the LEDs are turned ON. Approximately 2ms is required for the LED drive current to reach the set drive value. (1) If the EN signal is input after power is applied, the soft start time begins on the EN rising edge. The DIM pulse input for dimming is active during the soft start time. (2) After the soft start time (1.43ms) has elapsed, the LEDs are turned ON. Approximately 2ms is required for LED drive current to reach set values. Switching to Standby Mode The SM8135B switches from ×1.0/×1.5/×2.0 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. I If EN is LOW for longer than the enable hold time of 1.00ms (typ), the SM8135B 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. Soft start time and LED current Switching to standby mode, and EN hold time EN input signal LED current (1) (2)typ: 1.43ms Soft start time LED ON typ: 2ms CE hold time typ: 1.00ms EN LED current 1.0 or 1.5 Standby mode
SEIKO NPC CORPORATION —9 Boost Mode Auto-switching The SM8135B switches between ×1.0 mode (VIN through mode), ×1.5 mode (1.5-times charge pump boost), and ×2.0 mode (2.0-times charge pump boost) automatically in response to the operating state to reduce current consumption. The switching transition flow chart is shown in the following figure. This section describes the boost mode switching in response to insufficient LED drive current level detection. The next section describes the mode reset functions. Initially, when the LED drive current begins to flow, oper- ation begins in ×1.0 mode at the set current value if possible, without boosting the input voltage VIN. If the set current value cannot be attained in ×1.0 mode due to a VIN voltage drop or an increase in the set current value, a low-current detector circuit connected to each LED drive circuit is activated that switches the VOUT output to ×1.5 mode automatically, and the charge pump circuit starts boosting the voltage by 1.5 times. If the set cur- rent value still cannot be attained, the LED drive circuits are switched to ×2.0 mode, and the charge pump starts boosting the voltage by 2 times. Boost mode switching flow chart LED ON 1.0 mode ILED judgment 1.5 mode ILED judgment 1.5 mode 1.0sec ILED judgment sufficient insufficient insufficient 1.0sec 2.0 mode sufficient ILED judgment insufficient sufficient insufficient Mode reset 1.5 1.0 Mode reset 2.0 1.5 sufficient
SEIKO NPC CORPORATION —10 In ×1.0 mode, VIN = VOUT. However, the VOUT output does not always reach the electrical characteristics typi- cal rating of 4.9V . However, as long as an insufficient current condition is not detected, ×1.0 mode operation continues. In other words, VOUT may drop below 4.9V if sufficient LED drive current is flowing to counter the LED forward-bias voltage drop VF. The longer the device can operate in the high output efficiency ×1.0 mode, the lower the total current consumption and the longer the battery drive time can be extended. Furthermore, the more that low VF LEDs and lower LED drive current are used, the longer the device can operate automatically in ×1.0 mode. The LED low-current detector circuit switches the output boost mode whenever a single insufficient current condition is detected among the 4 channel LED drive currents, hence drive LEDs with small VF variation should be used to increase overall efficiency. If, after startup, a LED connection to the DIN pins is switched ON/OFF, the LED current detection circuit will operate incorrectly and normal boost mode switching does not occur. Also, if LED drive current control using a DIM pin is not used, the low-current detector circuit does not operate and the boost mode does not switch to either ×1.5 or ×2.0 mode. V IN voltage drop and VOUT output voltage VOUT mode switching time comparison due to drive LED “VF” variation VIN input voltage VOUT mode VOUT output voltage 4.9V 1.0 mode 1.5 mode 1.0 1.5 threshold 1.5 2.0 threshold Lack of LED current detect 2.0 mode High High VF LED Low VF LED VIN input Low 1.0 mode (high efficiency) 1.5 mode1.0 mode (high efficiency) 2.0 mode (low efficiency) 1.5 mode (low efficiency) 2.0 mode
SEIKO NPC CORPORATION —11 Mode Reset Function 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 SM8135B outputs a mode reset sig- nal 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. (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. Switching from ×1.5 mode to ×1.0 mode due to mode reset signal Mode hold L: hold VOUT output voltage ILED detector Mode reset 1.0sec/cycle 1.0 mode min 80µs max 200µs ILED detector ignore 4.9V VOUT mode (1) (2) (3) (4) 1.5 mode 1.5 mode
SEIKO NPC CORPORATION —12 A mode hold signal of 200 µs (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 V IN voltage drops and the V OUT 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 imme- diately 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 V OUT 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. VOUT drop due to mode reset signal (between ×1.5 and ×1.0 mode) Mode reset Mode hold (L: hold) ILED detector (H: lack) VOUT output voltage VIN input voltage 1.0sec 1.0 1.5 threshold 4.9V VOUT mode max 200µS
SEIKO NPC CORPORATION —13 The mode reset operation when in ×2.0 mode performs boost mode switching between ×2.0 mode and ×1.5 mode. Mode switching directly from ×2.0 mode to ×1.0 mode does not occur. (1) Mode switches from ×2.0 to ×1.5 mode on the rising edge of the mode reset signal. (2) A 200µs (max) mode hold time begins after switching to ×1.5 mode. LED drive current insufficient state is detected but the mode is not switched during this interval. (3) LED drive current insufficient signal is ignored during the mode hold time, but normal mode switching operation resumes when the mode hold time elapses. The mode reset function periodically tests the boost mode to try to maximize the duration of operation in the higher efficiency ×1.0 and ×1.5 modes in order to extend battery drive time. Thermal Shutdown Circuit (Overtemperature Protection Circuit) The SM8135B features a thermal shutdown circuit that operates whenever the IC temperature exceeds approx- imately 170°C for whatever reason, stopping the VOUT output. VOUT output recommences when the IC temper- ature falls below approximately 150°C. At output shutdown, the LED drive current DATA settings are stored. Switching from ×2.0 mode to ×1.5 mode due to mode reset signal Mode hold (L: hold) VOUT output voltage ILED detector Mode reset 1.0sec/cycle min 80µs max 200µs ILED detector ignore 4.9V VOUT mode 2.0 mode 1.5 mode 2.0 mode
SEIKO NPC CORPORATION —14 PERIPHERAL PARTS About the External Capacitors The best capacitors for use with the SM8135B 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. About the Input Capacitor "C4" The parts layout of PCB may merely cause the “V OUT” 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 unsta- ble output voltage. Table. The EIA three digit "TC" code Lower temperature limit High temperature limit Maximum allowable capacitance change from +25°C (0V DC) T = +22%/−33% U = +22%/−56% V = +22%/−82% For example : X5R
SEIKO NPC CORPORATION —15 TYPICAL APPLICATION CIRCUITS LED × 4, ILED MAX = 20mA Note. If the driving LED is less than 4 pcs, unused DIN pins should be connect to GND. Dimming and ON/OFF control is performed using pulse input on EN with a maximum LED current determined by resistor RSET (see P .6 “Setting LED current using pulse input on EN”). The HIGH-level and LOW-level pulsewidths for the pulse input on EN must be 3.0µs or longer (see “Electrical Characteristics”). VIN Control logic TSD Current control Current detect Mode control Output voltage control Protection C1PC1M C2PC2M VOUT DIN1 DIN2 DIN3 ISET DIN4 GND PGNDNC (open at any time) C4 = 1µF 2.7 to 4.6V C1 = 1µF C2 = 1 µF C3 = 1µF RSET = 120kΩ MAX 20mA 4 Charge pump 1/ 1.5/ 2 EN GND
SEIKO NPC CORPORATION —16 LED × 3, ILED MAX = 20mA Note. If the driving LED is less than 4 pcs, unused DIN pins should be connect to GND. Dimming and ON/OFF control is performed using pulse input on EN with a maximum LED current determined by resistor RSET (see P .6 “Setting LED current using pulse input on EN”). The HIGH-level and LOW-level pulsewidths for the pulse input on EN must be 3.0µs or longer (see “Electrical Characteristics”). VIN Control logic TSD Current control Current detect Mode control Output voltage control Protection C1PC1M C2PC2M VOUT DIN1 DIN2 DIN3 ISET DIN4 (connect to ground) GND PGNDNC (open at any time) C4 = 1µF 2.7 to 4.6V C1 = 1µF C2 = 1 µF C3 = 1µF RSET = 120kΩ MAX 20mA 3 Charge pump 1/ 1.5/ 2 EN GND
SEIKO NPC CORPORATION —17 LED × 2, ILED MAX = 29.3mA Note. If the driving LED is less than 4 pcs, unused DIN pins should be connect to GND. Dimming and ON/OFF control is performed using pulse input on EN with a maximum LED current determined by resistor RSET (see P .6 “Setting LED current using pulse input on EN”). The HIGH-level and LOW-level pulsewidths for the pulse input on EN must be 3.0µs or longer (see “Electrical Characteristics”). VIN Control logic TSD Current control Current detect Mode control Output voltage control Protection C1PC1M C2PC2M VOUT DIN1 DIN2 DIN3 (connect to ground) ISET DIN4 (connect to ground) GND PGNDNC (open at any time) C4 = 1µF 2.7 to 4.6V C1 = 1µF C2 = 1 µF C3 = 1µF RSET = 82kΩ MAX 29.3mA 2 Charge pump 1/ 1.5/ 2 EN GND
SEIKO NPC CORPORATION —18 FOOTPRINT PATTERN 3.6 ± 0.1 2.2 ± 0.1 2.2 ± 0.1 3.6 ± 0.1 0.25 ± 0.05 0.7 ± 0.1 0.32
SEIKO NPC CORPORATION —19 NC0707AE 2007.11 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 te sting or modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any ent ity not in compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are req uested 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: sales @npc.co.jp