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SC623
LED Light Management Unit
POWER MANAGEMENT Features
Input supply voltage range -- 3.0V to 5.5V Charge pump modes -- 1x, 1.5x and 2x Four programmable current sinks with 32 steps from 0.5mA to 25mA Flash LED -- 400mA max in flash mode, 250mA max continuous for spotlight Charge pump frequency -- 250kHz SemWireTM single wire interface -- up to 75kbit/s Backlight current accuracy 1.5% typical Backlight current matching 0.5% typical Programmable fade-in/fade-out for main backlight External flash control pin to sync with camera Optional 1s flash time out Automatic sleep mode (LEDs off ) -- IQ = 100A Low shutdown current -- 0.1A (typical) Ultra-thin package -- 3mm x 3mm x 0.6mm Fully WEEE and RoHS compliant
Charge Pump, 4 LEDs, 400mA Flash LED, and SemWireTM Interface Description
The SC623 is a high efficiency charge pump LED driver using Semtech's proprietary mAhXLifeTM technology. Performance is optimized for use in single-cell Li-ion battery applications. The charge pump provides backlight current in conjunction with four matched current sinks. It also can supply continuous or bursted current to a flash LED using the dedicated flash driver current sink. The load and supply conditions determine whether the charge pump operates in 1x, 1.5x, or 2x mode. An optional fading feature that gradually adjusts the backlight current is provided to simplify control software. A flash-timeout feature disables the flash if active for longer than 1 second. The SC623 uses the proprietary SemWireTM single wire interface. The interface controls all functions of the device, including backlight and flash currents. The single wire implementation minimizes microcontroller and interface pin counts. The flash/spotlight output is triggered via either the SemWire interface or a dedicated pin. In sleep mode, the device reduces quiescent current to 100A while continuing to monitor the serial interface. Total current reduces to 0.1A in shutdown.
Applications
Cellular phone backlighting and flash PDA backlighting and flash
Typical Application Circuit
MAIN BACKLIGHT VBAT CIN 2.2F VIN SemWire Interface Flash Control SWIF FLEN VOUT COUT 4.7F BL1 BL2 BL3 BL4 FL
FLASH
SC623
GREF AGND PGND C1+ C1C1 2.2F
C2+ C2C2 2.2F
US Patents: 6,504,422; 6,794,926 June 27, 2007
(c) 2007 Semtech Corporation
1
SC623
Pin Configuration Ordering Information
Device
C1+ C1C2+ VOUT
Package
MLPQ-UT-20 3x3 Evaluation Board
SC623ULTRT(1)(2) SC623EVB
20
VIN
19
18
17
16
C2PGND FL BL1 BL2
1 TOP VIEW 2 3 4 5 T
15 14 13 12 11
NC NC NC NC SWIF
Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Available in lead-free package only. Device is WEEE and RoHS compliant.
6
7
8
9
10
AGND
MLPQ-UT-20; 3x3, 20 LEAD JA = 35C/W
Marking Information
623 yyww xxxx
yyww = Date Code xxxx = Semtech Lot No.
GREF
FLEN
BL3
BL4
2
SC623
Absolute Maximum Ratings
VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0 VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +6.0 C1+, C2+ (V) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to (VOUT + 0.3) Pin Voltage -- All Other Pins (V) . . . . . . . . . -0.3 to (VIN + 0.3) VOUT Short Circuit Duration . . . . . . . . . . . . . . . . Continuous Short Circuit Duration . . . . . . . . . . . . . . . . . . . . . . Continuous ESD Protection Level(1) (kV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Recommended Operating Conditions
Ambient Temperature Range (C) . . . . . . . . -40 < TA < +85 VIN (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 < VIN < 5.5 VOUT (V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 < VOUT < 5.25 Voltage Difference between any two LEDs (V) . . . . . . < 1.2
Thermal Information
Thermal Resistance, Junction to Ambient(2) (C/W) . . . . 35 Maximum Junction Temperature (C) . . . . . . . . . . . . . . +150 Storage Temperature Range (C) . . . . . . . . . . . . -65 to +150 Peak IR Reflow Temperature (10s to 30s) (C) . . . . . . . +260
Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. NOTES: (1) Tested according to JEDEC standard JESD22-A114-B. (2) Calculated from package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
Electrical Characteristics
Unless otherwise noted, TA = +25C for Typ, -40C to +85C for Min and Max, TJ(MAX) = 125C, VIN = 3.0V to 4.2V, CIN= C1= C2= 2.2F, COUT = 4.7F (ESR = 0.03), VF 1.2V(1)
Parameter
Supply Specifications Shutdown Current
Symbol
Conditions
Min
Typ
Max
Units
IQ(OFF)
Shutdown, VIN = 4.2V Sleep mode, SWIF = VIN Charge pump in 1x mode, 4 backlights on
0.1 100 3.8 4.6 4.6
2 160 4.65 5.85 5.85
A A
Total Quiescent Current
IQ Charge pump in 1.5x mode, 4 backlights on Charge pump in 2x mode, 4 backlights on mA
Fault Protection Output Short Circuit Current Limit Over-Temperature Flash Mode Safety Timer(2) IOUT(SC) TOTP tFL(MAX) Flash sink active 0.75 VOUT pin shorted to GND 300 160 1.00 1.25 mA C s
3
SC623
Electrical Characteristics (continued)
Parameter Fault Protection (continued)
Charge Pump Over-Voltage Protection VOVP VUVLO Undervoltage Lockout VUVLO-HYS 300 mV VOUT pin open circuit, VOUT = VOVP rising threshold Decreasing VIN 5.3 5.7 2.4 6.0 V V
Symbol
Conditions
Min
Typ
Max
Units
Charge Pump Electrical Specifications
Maximum Total Output Current Backlight Current Setting Flash Current Setting Backlight Current Accuracy Backlight Current Matching Flash Current Accuracy 1x Mode to 1.5x Mode Falling Transition Voltage 1.5x Mode to 1x Mode Hysteresis 1.5x Mode to 2x Mode Falling Transition Voltage 2x Mode to 1.5x Mode Hysteresis Current Sink Off-State Leakage Current Pump Frequency IOUT(MAX) IBL IFL IBL_ACC IBL-BL IFL_ACC V TRANS1x VHYST1x V TRANS1.5x VHYST1.5x IBLn fPUMP VIN > 3.4V, sum of all active LED currents, VOUT(MAX) = 4.0V Nominal setting for BL1 thru BL4 Nominal setting for FL VIN = 3.7V, IBL = 12mA, TA = 25C VIN = 3.7V, IBL = 12mA(3) VIN = 3.7V, IFL = 400mA, TA = 25C IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V IOUT = 40mA, IBLn = 10mA, VOUT = 3.2V IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4) IOUT = 40mA, IBLn = 10mA, VOUT = 4.0V(4) VIN = VBLn = 4.2V VIN = 3.2V 500 0.5 50 -8 -3.5 -15 3.27 1.5 0.5 25 400 +8 +3.5 +15 mA mA mA % % % V
250
mV
2.92
V
300
mV
0.1 250
1
A kHz
4
SC623
Electrical Characteristics (continued)
Parameter Symbol Conditions Min Typ Max Units
Digital I/O Electrical Specifications (FLEN, SWIF) Input High Threshold Input Low Threshold Input High Current Input Low Current SemWire Bit Rate SemWire Start-up Time(5) SemWire Disable Time(6) SemWire Data Latch Delay(7) VIH VIL IIH IIL fSWIF tEN tDIS DDL VIN = 5.5V VIN = 3.0V VIN = 5.5V VIN = 5.5V -1 -1 10 1 10 5 1.6 0.4 +1 +1 75 V V A A kbit/s ms ms bit
Notes: (1) VF is the voltage difference between any two LEDs. (2) Once tripped, flash output will remain disabled until FLEN pin is cycled or reset via serial interface. (3) Current matching equals [IBL(MAX) - IBL(MIN] / [IBL(MAX) + IBL(MIN)]. (4) Test voltage is VOUT = 4.0V -- a relatively extreme LED voltage -- to force a transition during test. Typically VOUT = 3.2V for white LEDs. (5) The SemWire start-up time is the minimum period that the SWIF pin must be held high to enable the part before commencing communication. (6) The SemWire disable time is the minimum period that the SWIF pin must be pulled low to shut the part down. (7) The SemWire data latch delay is the maximum duration after communication has ended before the register is updated.
5
SC623
Typical Characteristics
Battery Current (4 LEDs) -- 25mA Each
160 VOUT=3.66V, IOUT=100mA, 25C
Battery Current (4 LEDs) -- 12mA Each
80 VOUT=3.50V, IOUT=48mA, 25C
150
73
Battery Current (mA)
Battery Current (mA)
140
66
130
59
120
110
52
100 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
45 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
Backlight Efficiency (4 LEDs) -- 25mA Each
100 VOUT=3.66V, IOUT=100mA, 25C
Backlight Efficiency (4 LEDs) -- 12mA Each
100 VOUT=3.50V, IOUT=48mA, 25C
90
90
% Efficiency
% Efficiency
80
80
70
70
60
60
50 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
50 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
Battery Current (4 LEDs) -- 5.0mA Each
40 VOUT=3.33V, IOUT=20mA, 25C
100
Backlight Efficiency (4 LEDs) -- 5.0mA Each
VOUT=3.33V, IOUT=20mA, 25C
35
90
Battery Current (mA)
% Efficiency
4.0 3.8 3.6 VIN (V) 3.4 3.2 3.0
30
80
25
70
20
60
15 4.2
50 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
6
SC623
Typical Characteristics (continued)
Flash Current -- 300mA
390 VOUT=3.58V at 25C
490
Flash Current -- 400mA
VOUT=3.39V at 25C
360
460
Flash Current (mA)
Flash Current (mA)
330
430
300
400
270
370
240
340 310 4.2
210 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
Spotlight Current -- 50mA
53 VOUT=3.02V at 25C
340
Spotlight Current -- 250mA
VOUT=3.50V at 25C
52
Spotlight Current (mA)
Spotlight Current (mA)
310
51
280
50
250
49
220
48 47 4.2
190 160 4.2
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
4.0
3.8
3.6 VIN (V)
3.4
3.2
3.0
7
SC623
Typical Characteristics (continued)
Output Short Circuit Current Limit
VOUT=0V, VIN=4.2V, 25C
Flash Mode Safety Timer
VIN=3.7V, 25C
VOUT (1V/div)
VFLEN (5V/div)
VOUT (2V/div)
IOUT (100mA/div) IFL (200mA/div)
Time (1ms/div)
Time (200ms/div)
Output Open Circuit Protection
VIN=3.7V, 25C VBL1 (500mV/div) VFLEN (5V/div)
Flash Current Pulse
IFL=400mA, VIN=3.7V, VOUT=3.7V, 25C
VOUT (2V/div)
VOUT (2V/div)
IBL1 (20mA/div)
IFL (200mA/div)
Time (200s/div)
Time (40ms/div)
8
SC623
Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 T
Pin Name
C2PGND FL BL1 BL2 BL3 BL4 AGND GREF FLEN SWIF NC NC NC NC VOUT C2+ C1+ VIN C1THERMAL PAD
Pin Function
Negative connection to bucket capacitor 2 -- requires a 2.2F capacitor connected to C2+ Ground pin for high current charge pump and Flash LED driver Current sink output for flash LED(s) Current sink output for main backlight LED 1 -- leave this pin open if unused Current sink output for main backlight LED 2 -- leave this pin open if unused Current sink output for main backlight LED 3 -- leave this pin open if unused Current sink output for main backlight LED 4 -- leave this pin open if unused Analog ground pin -- connect to ground and separate from PGND current Ground reference -- connect to ground Control pin for flash LED(s) -- high = ON, low = OFF SemWire single wire interface pin -- used to enable/disable the device and to set up all internal registers (refer to Register Map and SemWire Interface sections) Unused pin -- do not terminate Unused pin -- do not terminate Unused pin -- do not terminate Unused pin -- do not terminate Charge pump output -- all LED anode pins should be connected to this pin -- requires a 4.7F capacitor to PGND Positive connection to bucket capacitor 2 -- requires a 2.2F capacitor connected to C2Positive connection to bucket capacitor 1 -- requires a 2.2F capacitor connected to C1Battery voltage input -- connect with a 2.2F capacitor to PGND Negative connection to bucket capacitor 1 -- requires a 2.2F capacitor connected to C1+ Thermal pad for heatsinking purposes -- connect to ground plane using multiple vias -- not connected internally
9
SC623
Block Diagram
C1+ 18
C120
C2+ 17
C21 VOUT
VIN
19
VIN
mAhXLifeTM Fractional Charge Pump (1x, 1.5x, 2x)
16 2
VOUT PGND
SWIF
11 SemWireTM Digital Interface and Logic Control
Oscillator 4 5 6 Current Setting DAC 7 BL1 BL2 BL3 BL4
FLEN
10 9
GREF
NC
13
3
FL
NC
12 Bandgap Reference 15 14 NC NC
AGND
8
10
SC623
Applications Information
General Description
This design is optimized for handheld applications supplied from a single Li-Ion cell and includes the following key features: connected between the C2+ and C2- pins as shown in the typical application circuit diagram. These capacitors should be equal in value, with a minimum capacitance of 2.2F to support the charge pump current requirements. The device also requires a 2.2F capacitor on the VIN pin and a 4.7F capacitor on the VOUT pin to minimize noise and support the output drive requirements. Capacitors with X7R or X5R ceramic dielectric are strongly recommended for their low ESR and superior temperature and voltage characteristics. Y5V capacitors should not be used as their temperature coefficients make them unsuitable for this application.
* * * *
A high efficiency fractional charge pump that supplies power to all LEDs Four matched current sinks that control LED backlighting current, with 0.5mA to 25mA per LED An LED flash output that provides up to 400mA of momentary current or up to 250mA of continuous spotlight current A SemWire single wire interface that provides control of all device functions
LED Backlight Current Sinks
The backlight current is set via the SemWire interface. The current is regulated to one of 32 values between 0.5mA and 25mA. The step size varies depending upon the current setting. Between 0.5mA and 12mA, the step size is 0.5mA. The step size increases to 1mA for settings between 12mA and 15mA and 2mA for settings greater than 15mA. This feature allows finer adjustment for dimming functions in the low current setting range and coarse adjustment at higher current settings where small current changes are not visibly noticeable in LED brightness. All backlight current sinks have matched currents, even when there is variation in the forward voltages (VF ) of the LEDs. A VF of 1.2V is supported when the input voltage is at 3.0V. Higher VF LED mis-match is supported when VIN is higher than 3.0V. All current sink outputs are compared and the lowest output is used for setting the voltage regulation at the VOUT pin. This is done to ensure that sufficient bias exists for all LEDs, including the flash LED. The backlight LEDs default to the off state upon powerup. For backlight applications using less than four LEDs, any unused output must be left open and the unused LED driver must remain disabled. When writing to the Backlight Enable Control register, a zero (0) must be written to the corresponding bit of any unused output.
High Current Fractional Charge Pump
The backlight and flash outputs are supported by a high efficiency, high current fractional charge pump output at the VOUT pin. The charge pump multiplies the input voltage by 1, 1.5, or 2 times. The charge pump switches at a fixed frequency of 250kHz in 1.5x and 2x modes and is disabled in 1x mode to save power and improve efficiency. The mode selection circuit automatically selects the 1x, 1.5x or 2x mode based on circuit conditions. Circuit conditions such as low input voltage, high output current, or high LED voltage place a higher demand on the charge pump output. A higher numerical mode may be needed momentarily to maintain regulation at the VOUT pin during intervals of high demand, such as the high current of an LED flash or the droop at the VIN pin during a supply voltage transient. The charge pump responds to these momentary high demands, setting the charge pump to the optimum mode (1x, 1.5x or 2x), as needed to deliver the output voltage and load current while optimizing efficiency. Hysteresis is provided to prevent mode toggling. The charge pump requires two bucket capacitors for low ripple operation. One capacitor must be connected between the C1+ and C1- pins and the other must be
11
SC623
Applications Information (continued)
Backlight Quiescent Current
The quiescent current required to operate all four backlights is reduced by 1.5mA when backlight current is set to 4.0mA or less. This feature results in higher efficiency under light-load conditions. Further reduction in quiescent current will result from using fewer than four LEDs.
Shutdown State
The device is disabled when the SWIF pin is low. All registers are reset to default condition when SWIF is low.
Sleep Mode
When all LEDs are off, sleep mode is activated. This is a reduced current mode that helps minimize overall current consumption by turning off the clock and the charge pump while continuing to monitor the serial interface for commands.
Fade-In and Fade-Out
Backlight brightness can be set to automatically fade-in when current is set to increase and fade-out when current is set to decrease. When enabled with a new current setting, the current will step through each incremental setting between the old and new values. The result is a visually smooth change in brightness with a rate of fade that can be set to 8, 16, 24, or 32 ms per step.
SemWire Single Wire Interface Functions
All device functions can be controlled via the SemWire single wire interface. The interface is described in detail in the SemWire Interface section of the datasheet.
LED Flash and Spotlight Current Sink
A single output current sink is provided to drive both flash and spotlight functions. In flash mode, this current sink provides up to 400mA for a flash LED or array of parallel LEDs. Flash current settings are in 50mA increments from 50mA to 400mA. The FLEN pin directly triggers the FLASH function when pulled high, or it can be wired to VIN to enable software control via the serial interface. In spotlight mode, the output can be set for up to 250mA of continuous current. Settings are available in 50mA increments from 50mA to 250mA. Continuous operation above 250mA is not recommended due to high power dissipation.
Protection Features
The SC623 provides several protection features to safeguard the device from catastrophic failures. These features include:
* * * *
Output Open Circuit Protection Over-Temperature Protection Charge Pump Output Current Limit LED Float Detection
Flash and Spotlight Safety Timer
A safety timer disables the flash and spotlight output current sink if the sink remains active for an extended period. The timer protects the SC623 and the LED from high power dissipation that can cause overheating. The timer's default state is on, but the timer may be disabled via the serial interface to allow continuous output current in spotlight mode. The safety timer affects only the FL pin and will turn off the sink after a period of 1 second. The timer may be reset by either forcing the FLEN pin low or by resetting the Flash/Spotlight control bits via the interface.
Output Open Circuit Protection Over-Voltage Protection (OVP) is provided at the VOUT pin to prevent the charge pump from producing an excessively high output voltage. In the event of an open circuit at VOUT, the charge pump runs in open loop and the voltage rises up to the OVP limit. OVP operation is hysteretic, meaning the charge pump will momentarily turn off until VOUT is sufficiently reduced. The maximum OVP threshold is 6.0V, allowing the use of a ceramic output capacitor rated at 6.3V with no fear of over-voltage damage.
12
SC623
Applications Information (continued)
Over-Temperature Protection The Over-Temperature (OT) protection circuit helps prevent the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 160C, the device goes into thermal shutdown with all outputs disabled until the junction temperature is reduced. All register information is retained during thermal shutdown. Charge Pump Output Current Limit The device also limits the charge pump current at the VOUT pin. When VOUT is shorted to ground, the typical output current limit is 300mA. The current limiting is triggered by an output under-voltage lockout below 2V. The output returns to normal when the short is removed and VOUT is above 2.5V. Above 2.5V, a typical current limit of 300mA applies when the FL current sink is off and a typical current limit of 1A applies when the FL current sink is on. LED Float Detection Float detect is a fault detection feature of the LED current sink outputs. If an output is programmed to be enabled and an open circuit fault occurs at any current sink output, that output will be disabled to prevent a sustained output OVP condition from occurring due to the resulting open loop. Float detect ensures device protection but does not ensure optimum performance. Unused LED outputs must be disabled to prevent an open circuit fault from occurring.
13
SC623
Applications Information (continued)
PCB Layout Considerations
The layout diagram in Figure 1 illustrates a proper two-layer PCB layout for the SC623 and supporting components. Following fundamental layout rules is critical for achieving the performance specified in the Electrical Characteristics table. The following guidelines are recommended when developing a PCB layout:
* * *
* *
*
Place all bypass and decoupling capacitors -- C1, C2, CIN, and COUT as close to the device as possible. All charge pump current passes through VIN, VOUT, and the bucket capacitor connection pins. Ensure that all connections to these pins make use of wide traces so that the resistive drop on each connection is minimized. The thermal pad should be connected to the ground plane using multiple vias to ensure proper thermal connection for optimal heat transfer.
Make all ground connections to a solid ground plane as shown in the example layout (Figure 3). If a ground layer is not feasible, the following groupings should be connected: PGND -- CIN, COUT AGND -- Ground Pad If no ground plane is available, PGND and AGND should be routed back to the negative battery terminal as separate signals using thick traces. Joining the two ground returns at the terminal prevents large pulsed return currents from mixing with the low-noise return currents.
GND
CIN
C1
C2
VOUT
COUT
VIN
GND
C2-
C1-
VOUT
Figure 2 -- Layer 1
NC
C1+
PGND
C2+
VIN
NC
FL
SC623
NC
BL1
NC
BL2
SWIF
AGND
GREF
BL3
Figure 1 -- Recommended PCB Layout Figure 3 -- Layer 2
BL4
FLEN
14
SC623
Register Map
Address D7 D6 D5 D4 D3 D2 D1 D0 Reset Value
0x00
Description
Backlight Current Control Backlight Enable Control Flash/Spotlight Control
0x00
FADE_1
FADE_0
FADE_EN
BL_4
BL_3
BL_2
BL_1
BL_0
0x01
0(1)
0(1)
0(1)
0(1)
BLEN_4
BLEN_3
BLEN_2
BLEN_1
0x00
0x02
0(1)
0(1)
0(1)
FLTO
FL_2
FL_1
FL_0
FL/SPLB
0x10
Notes: (1) 0 = always write a 0 to these bits
Register and Bit Definitions
Backlight Current Control Register (0x00)
This register is used to set the currents for the backlight current sinks, as well as to enable and set the fade step rate. These current sinks need to be enabled in the Backlight Enable Control register to be active. FADE[1:0] These bits are used to set the rise/fall rate between two backlight currents as follows:
FADE_1
0 0 1 1
FADE_0
0 1 0 1
Fade Feature Rise/Fall Rate (ms/step)
32 24 16 8
value to a new value set by bits BL[4:0] at a rate of 8ms to 32ms per step. A new backlight level cannot be written during an ongoing fade operation, but an ongoing fade operation may be cancelled by resetting the fade bit. Clearing the fade bit during an ongoing fade operation changes the backlight current immediately to the value of BL[4:0]. The number of counts to complete a fade operation equals the difference between the old and new backlight values to increment or decrement the BL[4:0] bits. If the fade bit is cleared, the current level will change immediately without the fade delay. The rate of fade may be changed dynamically, even while a fade operation is active, by writing new values to the FADE_1 and FADE_0 bits. The total fade time is determined by the number of steps between old and new backlight values, multiplied by the rate of fade in ms/step. The longest elapsed time for a full scale fade-out of the backlight is nominally 1.024 seconds when the default interval of 32ms is used.
The number of steps in changing the backlight current will be equal to the change in binary count of bits BL[4:0]. FADE_EN This bit is used to enable or disable the fade feature. When the fade function is enabled and a new backlight current is set, the backlight current will change from its current
15
SC623
Register and Bit Definitions (continued)
BL[4:0] These bits are used to set the current for the backlight current sinks. All enabled backlight current sinks will sink the same current, as shown in Table 1. Table 1 -- Backlight Current Control Bits
BL_4 BL_3 BL_2 BL_1 BL_0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
BL Enable Control Register (0x01)
This register is used to enable the backlight current sinks. BLEN[4:1] These bits are used to enable current sinks (active high, default low). BLEN_4 -- Enable bit for backlight BL4 BLEN_3 -- Enable bit for backlight BL3 BLEN_2 -- Enable bit for backlight BL2 BLEN_1 -- Enable bit for backlight BL1 When enabled, the current sinks will carry the current set by the backlight current control bits BL[4:0], as shown in Table 1. Flash/Spotlight Control Register (0x02) This register is used to configure the flash time-out feature, the flash or spotlight current, and select flash or spotlight current ranges. FLTO This bit is used to enable the flash safety time-out feature. The default state is enabled with FLTO = 1. If this bit is set, the device will turn off the flash after a nominal period of 1s. Two ways to re-enable the flash function after a safety time-out are: Pull the FLEN pin low to re-enable the flash function Clear and re-write FL[2:0]
Backlight Current (mA)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 13 14 15 17 19 21 23 25
* *
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SC623
Register and Bit Definitions (continued)
FL[2:0] These bits are used to set the current for the flash current sink when configured for flash or spotlight by the FL/SPLB bit. Bits FL[2:0] set the flash or spotlight current, as shown in Table 2. Table 2 -- Flash/Spotlight Control Bits
FL_2
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
FL_1
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
FL_0
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
FL/ SPLB
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
Flash/Spotlight Current (mA)
OFF 50 100 150 200 250 250 250 OFF 300(1) 350(1) 400(1) 400(1) 400(1) 400(1) 400(1)
FL/SPLB This bit is used to select either the flash or spotlight current ranges. If this bit is set, the FL current sink can be used to drive a flash of maximum duration 500ms and the current range will be the high (flash) current range. If this bit is cleared, the FL current sink can be used to drive a continuous spotlight at a lower current and the current range will be the lower (spotlight) current range, as shown in Table 2.
Note: (1) When on continuously, the device may reach the temperature limit with 300mA and higher.
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SC623
SemWire Interface
Semwire Interface Functions
The SWIF pin is a write-only single wire interface. It provides the capability to address up to 32 registers to control device functionality. The protocol for using this interface is described in the following subsections. Driving the SWIF Pin The SWIF pin should be driven by a GPIO from the system microcontroller. The output level can be configured as either a push-pull driver (TTL or CMOS levels) or as an open drain driver with an external pull-up resistor. Enabling the Device The SWIF pin must be pulled from low to high for a period of greater than 1ms (tEN) to enable the device into the sleep state. In the sleep state, the device bandgap is active, UVLO monitoring is active, and the serial interface is monitored for communication. Automatic Sleep State If both the backlight and flash current sinks are disabled, the device automatically enters the sleep state in order to minimize the current draw from the battery. When in sleep mode, the charge pump and oscillator are both disabled. Disabling the Device The SWIF pin must be pulled from high to low for a period greater than 10ms (tDIS) in order to shut down the device. In this state the device remains disabled until the SWIF pin is pulled high for a period greater than 1ms. All registers return to the default state, resetting all bits to zero except for FLT0, which defaults to one.
SemWire Communication Protocol and Timing
The following six step communication sequence controls all device functions when the device is enabled. 1. OSC On -- The SWIF pin is toggled low for one bit duration and high for one bit duration in order to enable the oscillator. The oscillator is turned off in the sleep state to minimize quiescent current. 2. Sample -- The SWIF pin is toggled low for one bit duration and high for one bit duration. During this time, the device samples the bit rate and determines the bit rate at which the register address and data values that follow will arrive. The sample rate is at least 20 times the bit rate ensuring robust communication synchronization. 3. Start -- The SWIF pin is pulled low for one bit duration, which starts communication with the target register. 4. Address -- The next 5 bits are the address of the target register -- MSB first, LSB last. 5. Data -- The next 8 bits are the data written to the target register -- MSB first, LSB last. 6. Standby -- After the last data bit is sent, the SWIF pin is pulled high for 5 bit durations to return the device to standby before another data write can take place. If all LEDs are disabled, the device will go back to sleep mode. NOTE: The bit rate must be set by the host controller to a rate that is between the minimum and maximum frequencies listed in the Electrical Characteristics section.
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SC623
SemWire Interface (continued)
Single Write Operation
Device Disabled Device Enabled Into Sleep OSC On Sample Register Address Data
5 Resume high Sleep if bits all LEDs Min. are off Device Disabled when low for tDIS
Start A4 t > tEN
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
t > DDL t > tDIS
Concatenated Write Operation
OSC On Sample Register Address Data OSC On (Repeated) D2 D1 D0 t > DDL Sample
Start
A4
A3
A2
A1
A0
D7
D6
D5
D4
D3
Start
To concatenate write operations, repeat Osc On, Sample and Start after the DO bit of the previous sequence as shown.
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SC623
Outline Drawing -- MLPQ-UT-20 3x3
B
A
D
DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX
A A1 A2 b D D1 E E1 e L N aaa bbb .020 .000 .024 .002 0.50 0.00 0.60 0.05 (.006) .006 .008 .010 .114 .118 .122 .061 .067 .071 .114 .118 .122 .061 .067 .071 .016 BSC .012 .016 .020 20 .003 .004 (0.1524) 0.15 0.20 0.25 2.90 3.00 3.10 1.55 1.70 1.80 2.90 3.00 3.10 1.55 1.70 1.80 0.40 BSC 0.30 0.40 0.50 20 0.08 0.10
PIN 1 INDICATOR (LASER MARK)
E
A2 A aaa C A1 e LxN E/2 E1
2 1 N
SEATING PLANE C D1
D/2 bxN bbb
NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
CAB
2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS . 3. DAP is 1.90 x 190mm.
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SC623
Land Pattern -- MLPQ-UT-20 3x3
H R DIM C G H K P R X Y Z DIMENSIONS INCHES (.114) .083 .067 .067 .016 .004 .008 .031 .146 MILLIMETERS (2.90) 2.10 1.70 1.70 0.40 0.10 0.20 0.80 3.70
(C)
K
G
Z
Y X P NOTES: 1. 2.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE.
3.
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com
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