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STLD20CP1
Power management for white LED and camera flash
Features

Inductor step-up to 17 V output for 2 to 4 white LEDs in series from 2.8 V to 6 V supply Charge pump 2X, 1X output for 1 power flash/torch WLED Control pins to select shutdown mode Single-wire pulse dimming control for white LED External resistor to set max current up to 300 mA in flash mode External resistor to set max current up to 100 mA in torch mode Logic input to select flash/strobe or movie/torch mode Soft start limits inrush current Internally limited inductor peak current Over-voltage and over-temperature protection. Package: QFN16 (3x3 mm) Temperature range: -40 C to 85 C
QFN16 (3x3 mm)
Description
The STLD20CP1 is a power management device for the supply of white LED TFT backlighting MAIN/SUB display and camera flash. It is a 1.3 MHz PWM step-up switching regulator and 2X and 1X charge pump. The current feedback control of the step-up provides excellent line transient response, making it particularly
suitable for battery-powered applications. It is possible to select the value of the current flowing through the power white LED using two external resistors to choose the current value in torch mode or flash mode. Single-wire pulse dimming control and shutdown of the white LEDs for backlighting is obtained through two digital control pins: DM1 and DM2. The flash is driven by two logic pins: TF, to enable the flash function, and SEL to select torch or flash mode. Other features include over-voltage and over-temperature protection, and inductor current limitation. The high efficiency of the STLD20CP1 makes it suitable for hand-held instruments and particularly ideal in mobile phones. The STLD20CP1 is available in a small, thin lowprofile QFN16 (3x3 mm) package.
Table 1.
Device summary
Order code STLD20CP1PQR Package QFN16 (3x3 mm) Packaging Tape and reel
November 2007
Rev 2
1/19
www.st.com 19
Contents
STLD20CP1
Contents
1 2 3 4 5 6 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Step-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Shutdown and brightness control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Peak inductor current limitation and soft start function . . . . . . . . . . . . . . . 11 Charge pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Current on power LED (flash) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Over-voltage and short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . 11 Start-up procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7 8
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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STLD20CP1
Diagram
1
Figure 1.
Diagram
Block diagram
3/19
Pin description
STLD20CP1
2
Figure 2.
Pin description
Pin configuration (top view)
Table 2.
Symbol SGND DM1 DM2 FB_SU OUT_SU IN SW PGND CN CP FB_CP OUT_CP TF IT IF SEL
Pin description
Pin n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Signal ground Logic input to control current through the white LEDs, and shutdown mode function on backlight Logic input to control current through the white LEDs, and shutdown mode function on backlight Feedback of step-up. Control current pin on backlight Sensing of the step-up output voltage in order to provide protection in case of the output voltage exceeds OVP threshold Supply voltage of the device Switch node. The internal N-channel drain is connected to this pin Power ground Negative input for the external charge pump capacitor Positive input for the external charge pump capacitor Feedback of charge pump. Control current pin on flash Out of the charge pump 2X, 1X Logic input to enable charge pump A resistor connected between this pin and IN sets the maximum value of current in torch mode (SEL=0) A resistor connected between this pin and IN sets the maximum value of current in flash mode (SEL=1) Logic input to control flash mode. (see truth table charge pump) Description
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STLD20CP1
Maximum ratings
3
Table 3.
Symbol IN SW OUT_SU FB_SU OUT_CP FB_CP PGND IT IF CP CN TF SEL DM2 DM1 PD TSTG TOP VESD
Maximum ratings
Absolute maximum ratings
Parameter DC supply Switch node Output step-up Feedback step-up Output charge pump Feedback of charge pump Power ground Torch current selection Flash current selection Pumping capacitor positive pin Pumping capacitor negative pin Charge pump enable Logic input to control flash or torch mode Logic input to control current of white LEDs Logic input to control current of white LEDs Power dissipation Storage temperature range Ambient operating temperature ESD rating Value From -0.3 to 7 From -0.3 to 20 From -0.3 to 20 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 0.3 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 From -0.3 to 7 Internally Limited -65 to 150 -40 to 85 3 Unit V V V V V V V V V V V V V V V mW C C KV
Note:
Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Thermal data
Parameter Thermal resistance junction-ambient Thermal resistance junction-case Value 49.1 4.216 Unit C/W C/W
Table 4.
Symbol RthJA RthJC
5/19
Truth tables
STLD20CP1
4
Table 5.
Truth tables
Truth table selection mode step-up
DM1 0 0 1 1 DM2 0 1 0 1 Mode Shutdown step-up 5% dimming 60% dimming 100% dimming
Table 6.
Truth table selection mode charge pump
SEL X 0 1 TF 0 1 1 Mode Shutdown charge pump Torch mode Flash mode ON
Figure 3.
Typical application circuit
6/19
STLD20CP1
Electrical characteristics
5
Table 7.
Electrical characteristics
Electrical characteristics for STLD20CP1 (TJ = -40 C to 85 C, VI = 3.4 V, CI = 2.2 F, CO1,2 = 2.2 F, VO_SU = 15 V, VO_CP = 4 V, CCP = 1 F, CFB_SU = 100 pF, L = 3.3 H, DM1 = DM2 = 1.6 V, typ. values @ 25 C, unless otherwise specified)
Parameter Test conditions Min. Typ. Max. Unit
Symbol Supply section VI VUVLO_H VUVLO_L II
Operating input voltage Under-voltage lockout HIGH Under-voltage lockout LOW Supply current Standby current ILED = 50mA, TF = 0 DM1= DM2 = TF = SEL = 0
2.8
6 2.7
V V V
2.2 700 1
A A
Dynamic performance Efficiency step-up ILED = 20mA, VI = 2.8V to 6.0V (1) 80 %
Backlight section, step-up V_OVP VFB_SU IFB_SU fSW Over-voltage protection Feedback voltage Feedback leakage current VFB_SU = 1V Frequency switching 16.5 465 490 0.1 1.3 515 0.5 V mV A MHz
Backlight section, step-up RDSON P_SW ILK_SW IPK VRipple ILED MAX Step-up switch resistance P_SW leakage current Peak inductor current Output ripple step-up Max LED current ILED = 50mA VFB_SU/R_LED, R_LED = 10 VI = 3.0V to 4.2V @ TJ = 25C R_LED = 10
(1)
TJ = 25C, ISW = 100mA VSW = 17V, DM1= DM2 = 0V
0.8 0.1 1,2 30 50 -5 10 5 0.5
A A mVpp mA % mV
ILED (LINE) Static line regulation FB step STEP feedback voltage
Digital control section V-DM1H V-DM2H V-TFH V-SELH I-DM1H I-DM2H I-TFH I-SELH
High voltage threshold
VI = 2.8V to 6V
1.4
V
I-DM1H leakage current I-DM2H leakage current I-TFH leakage current I-SELH leakage current
V-DM1H = 6V V-DM2H = 6V V-TFH = 6V V-SELH = 6V
0.1 0.1 0.1 0.1
0.5 0.5 0.5 0.5
A A A A 7/19
Electrical characteristics Table 7.
STLD20CP1
Electrical characteristics for STLD20CP1 (continued) (TJ = -40 C to 85 C, VI = 3.4 V, CI = 2.2 F, CO1,2 = 2.2 F, VO_SU = 15 V, VO_CP = 4 V, CCP = 1 F, CFB_SU = 100 pF, L = 3.3 H, DM1 = DM2 = 1.6 V, typ. values @ 25 C, unless otherwise specified)
Parameter Test conditions Min. Typ. Max. Unit
Symbol
V-DM1L VDM2L VLow voltage threshold TFL V-SELL I-DM1L I-DM2L I-TFL I-SELL I-DM1L leakage current I-DM2L leakage current I-TFL leakage current I-SELL leakage current
VI = 2.8V to 6V
0.6
V
V-DM1L = 0V V-DM2L = 0V V-TFL = 0V V-SELL = 0V
0.1 0.1 0.1 0.1
0.5 0.5 0.5 0.5
A A A A
Single-wire pulse dimming TLO THI TSHDN Initial THI Duration time of the low pulse Duration time of the high pulse Duration time to shut down the current Duration time required for the first pulse 50 0.5 0.5 500 250 s s s s
Flash section charge pump VIF VIT VFB_CP VO_CP Voltage threshold Voltage threshold Feedback charge pump Over voltage charge pump Flash mode @ VI 3V
(1)
Flash mode Torch mode I_Torch = 100mA
VI-0.6 VI-0.6 150 6 300
V V mV V mA 130
IO_CP Max Max current charge pump Flash section charge pump I_Flash I_Flash
(LINE)
Torch mode @ VI 3V (1)
Accuracy current flash Static line regulation current flash Accuracy current torch Static line regulation current torch
VI = 3.4V, RFL = 1950 K*VIF/RFL = I_Flash, VI = 3.0V to 4.2V @ TJ = 25C VIN = 3.4V, RTH = 7800 K*VIT/RTH = I_Torch, VI = 3.0V to 4.2V @ TJ = 25C
-10 -10 -10 -10
10 10 10 10
% % % %
I_Torch I_Torch
(LINE)
Thermal shutdown TSD THS Thermal shutdown Thermal shutdown hysteresis 180 20 C C
1. Guaranteed by design.
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STLD20CP1
Application information
6
6.1
Application information
Step-up
The STLD20CP1 is a PWM controller working at a 1.3 MHz frequency, designed to function in discontinuous mode. The LED current regulation for the backlighting is achieved by connecting the FB_SU terminal at the top end of the external RLED resistance. ILED = VFB_SU/RLED
6.2
Shutdown and brightness control
The shutdown and brightness control functions are achieved by using the digital control pins DM1 and DM2. There are also other modes that can be used to perform dimming control on white LEDs. The first is to use the truth table selection mode step-up that shows the behavior using a preselected digital dimming control. The second is a PWM dimming control mode, which is implemented by keeping a DMx pin at a low or high value and the other DMx forcing a PWM digital signal up to 50 kHz with a minimum duty cycle 5%. A 5% duty cycle corresponds to the minimum current and a 100% duty cycle corresponds to full current. In cases where DM2 is a high value and DM1 is forced with a PWM digital (Figure 4), the dimming control varies from 5% to 100% of current. If DM2 is held low and the PWM signal is applied on DM1 (Figure 5), the dimming control varies from 0 up to 60% of current.
Figure 4.
PWM dimming method from 5% to 100%
9/19
Application information Figure 5. PWM dimming method from 0% to 60%
STLD20CP1
Likewise, by forcing DM1 low and applying a PWM signal on pin DM2, is it possible to achieve dimming from 0 to 5% (Figure 6), while putting DM1 high and the PWM signal on DM2, the device performs dimming from 60% to 100% (Figure 7). Figure 6. PWM dimming method from 0% to 5%
Figure 7.
PWM dimming method from 60% to 100%
The third way is to utilize single-wire pulse dimming by connecting DM1 and DM2 together. This feature allows the selection of additional steps of LED current through a digital signal coming from the microprocessor, reducing the number of control traces on the PCB. When the DM1 and DM2 are simultaneously high, the high current value is selected on the LEDs, and each additional pulse reduces the LED current by 10%. After the tenth pulse, the LED
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STLD20CP1
Application information current reaches 5%. The eleventh pulse sets the LED current back to ILED max. Figure 8 shows a timing diagram for single-wire pulse dimming. Analog dimming can be achieved by connecting a resistor network to the FB pin (Figure 9).
6.3
Peak inductor current limitation and soft start function
An integrated current sensor will sense the peak drain current of the switch P_SW in order to keep the inductor current below its saturation level. Since the peak drain current exceeds the fixed limit IPK by the drain current reference, the comparator turns off the switch P_SW. During start up, this peak drain current limitation behaves inherently as a soft-start function.
6.4
Charge pump
The charge pump includes soft-start circuitry to limit inrush current at turn-on or when the device changes operation from x1 to x2. During the soft-start time, the output current is set to 10% of the maximum set by RTH or RFL (depending on the state of the SEL pin), until VFB_CP reaches regulation. This function is implemented to avoid battery stress. At start-up, the pin OUT_CP goes to VIN, working in an x1 condition. Following this phase, if VFB_CP >150 mV, the LED current is regulated and the device continues to operate in a 1x condition. Otherwise, if VFB_CP <150 mV, the device changes to a 2x operating condition bringing VOUT_CP>VIN. allowing LED current regulation. The device will change back to 1x mode when the input voltage rises above VOUT_CP by approximately 50 mV.
6.5
Current on power LED (flash)
The current that level flowing through the power LED in both modes (torch and flash) can be selected using the following formula: IFLASH = K (0.6/RFL), ITORCH = K (0.6/RTH) where K is a value of approximately 1220. Figure 10 shows the relationship between the TF signal control and flash duration time for one camera shot, while Figure 11 represents multiple shots.
6.6
Over-voltage and short-circuit protection
In case of open-circuit failure of the power LED, the output voltage is limited to about 5.5 V by gating the charge pump on/off. If the power LED experiences a short-circuit or if the output charge pump is grounded, the charge pump is turned off.
6.7
Start-up procedure
Before inserting the driving preferences with the digital pins it is mandatory to turn on the device with correct supply voltage with all the digital pins set to GND.
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Application information
STLD20CP1
6.8
Thermal shutdown
The device includes a thermal limit circuit that shuts down the IC at approximately +180 C, and return to operation after the IC cools by approximately 20 C.
Figure 8.
Single-wire pulse dimming
Figure 9.
Analog continuous dimming
12/19
STLD20CP1
Application information
Figure 10. Single camera shot
Figure 11. Multiple shots (graph is not to scale)
13/19
Package mechanical data
STLD20CP1
7
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) packages. These packages have a lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com
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STLD20CP1
Package mechanical data
QFN16 (3x3 mm) mechanical data
mm. Dim. Min. A A1 A3 b D D2 E E2 e K L r 0.30 0.09 1.55 1.55 0.18 0.80 Typ. 0.90 0.02 0.20 0.25 3.00 1.70 3.00 1.70 0.50 0.20 0.40 0.50 0.012 0.006 1.80 0.061 1.80 0.061 0.30 0.007 Max. 1.00 0.05 Min. 0.032 Typ. 0.035 0.001 0.008 0.010 0.118 0.067 0.118 0.067 0.020 0.008 0.016 0.020 0.071 0.071 0.012 Max. 0.039 0.002 inch.
E
A K A1
E2
e D b K r D2
A3
L
This drawing is not to scale
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Package mechanical data
STLD20CP1
Tape & reel QFNxx/DFNxx (3x3) mechanical data
mm. Dim. Min. A C D N T Ao Bo Ko Po P 3.3 3.3 1.1 4 8 12.8 20.2 60 14.4 0.130 0.130 0.043 0.157 0.315 Typ. Max. 180 13.2 0.504 0.795 2.362 0.567 Min. Typ. Max. 7.087 0.519 inch.
16/19
STLD20CP1
Package mechanical data
Figure 12. QFN16 (3x3 mm) footprint recommended data
17/19
Revision history
STLD20CP1
8
Table 8.
Date
Revision history
Document revision history
Revision 1 2 Initial release. Modified: Table 1. Changes
14-Nov-2007 20-Nov-2007
18/19
STLD20CP1
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