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PRELIMINARY CM9142 Two Group, 4 and 2, WLED Driver, Different Current Settings
Features
* * * * * * * * * * * * * * * * * * 2.9V to 6V input voltage range Powers two display backlight and/or flash WLEDs Low external parts count, requires no inductor and ballast resistors Low EMI and reflected ripple Adaptive charge pump ratio (1x or 1.5x) maximizes efficiency at both high and low input voltage Precision current regulation for each output with 2% current matching at 20mA Programmable LED current via ISET1 and ISET2 Independent Analog and PWM brightness control Independent current setting for each group Typical 500-kHz fixed switching frequency Supports up to 300mA, drives six LEDs regulated to 50mA each Less than 10A shutdown current Over-current and over-temperature protection Short circuit protection with auto shutdown Undervoltage lockout Soft-start limits start-up inrush current 16 lead TQFN package Optional RoHS compliant lead free package
Product Description
The CM9142 is an adaptive fractional switched capacitor (charge pump) regulator optimized for driving two groups, 4 and 2, of white LEDs Each group features individual ON/OFF controls and individually set current. Each LED's driver current is matched to within 2% for uniform intensity. It supports an input voltage range of 2.9V to 6V, with undervoltage lockout. A failure detection circuit prevents the loss of power when one or more LEDs fail (short or open). Internal over-temperature and over-current management provide short circuit protection. The CM9142 regulates up to 300mA of output current to drive WLEDs, allowing up to 50mA per LED channel. The maximum LED current for each group is programmed with external resistors. Master plus two independent enable inputs allows for Analog and PWM brightness control for each display. Either display can also be used for a camera flash. In full shutdown mode, the CM9142 draws only 10A. The CM9142 automatically selects the most efficient charge pump ratio based on the operating voltage requirement of the white LEDs. The proprietary design architecture maintains high efficiency (> 80%), and at low VIN provides longer battery life. With a high VIN, or when the adapter is powered, it provides cool reliable operation. The CM9142 is available in a compact 16 lead TQFN package. It can operate over the industrial temperature range of -40C to 85C.
Applications
* * * * Drive white LEDs for STN/TFT Color LCD backlighting Cell phones, PDAs, with multiple displays Digital Still Cameras Flash for DSC
Typical Application
1.0uF C1P C1N VIN 1uF
1.0uF C2P C2N VOUT LED1
Display 1
2.9V to 6.0V
1uF
off
on
Enable
EN ISET1
PhotonICTMLED2 CM9142
LED3 LED4 LED5 LED6
Display 2
RSET1
RSET2
ISET2 GND
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PRELIMINARY CM9142
Package Pinout
PACKAGE / PINOUT DIAGRAM
Bottom View
6 LED5 7 LED6 5 SET2 8 C2N
ISET1 VIN C1P LED1
4 3 2 1 16 15 14 13
9 EN
TQFN16 4X4
10 GND 11 C1N 12 LED4
LED3
LED2
16-Lead TQFN Package (4mm x 4mm)
Note: This drawing is not to scale.
Ordering Information
PART NUMBERING INFORMATION
Lead-free Finish Leads 16 Package TQFN Ordering Part Number1 CM9142-01QE Part Marking
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
Specifications
ABSOLUTE MAXIMUM RATINGS
PARAMETER ESD Protection (HBM) Pin Voltages VIN to GND VOUT to GND ISET1, ISET2, EN to GND All other pins to GND Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10s) RATING 2 [GND - 0.3] to +6.0 [GND - 0.3] to +7.0 [GND - 0.3] to +5.0 [GND - 0.3] to +5.0 -65 to +150 -40 to +85 300 UNITS kV V V V C C C
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VOUT
C2P
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PRELIMINARY CM9142
Specifications (cont'd)
ELECTRICAL OPERATING CHARACTERISTICS
VIN = 3.6V; All outputs are on. Typical values are at TA = 25C. SYMBOL VIN VUVLO IQ ISD PARAMETER Supply Voltage Range Undervoltage Lockout Quiescent Current Shutdown Supply Current All outputs are no load. 1x mode VEN < 0.4V IOUT = 0mA to 120mA, VIN = 3.0 to 5.5V 4.2 CONDITIONS MIN 2.9 1.7 1.8 500 2 10 5.5 300 1 2 5 50 1.8 0.4 400 135 15 mA C C TYP MAX 6.0 1.9 UNIT S V V A A V mA % % mA
VOUT Charge Pump Output Voltage VOUT ILED TOT ILED Accuracy of ISET Matching current between LED1 to LED6 ILED per driver EN, ISET VIH VIL Protection Over-current Limit Over-temperature Limit Over-temperature Hysteresis High Level Input Voltage Low Level Input Voltage Total ILED Current
ILED1 thru ILED4+photoflash
VIN = 3.0V to 5.5V VIN = 4.0V, ILED 1 to ILED6= 20mA Device total ILED < 300mA
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PRELIMINARY CM9142
Typical Performance Curves
Charge Pump Efficiency
Vled=3.2V 100 200
Source Current
Vled=3.2V
Efficiency (%)
90
Input Current (mA)
175 150 125 100 75 50 25 3.0
Iout=60mA Iout=30mA Iout=120mA
80
Iout=120mA Iout=30mA Iout=60mA
70
60 3.0
3.5
4.0
4.5
5.0
5.5
6.0
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
Input Voltage (V)
Typical Waveforms
Cin=C2=C3=Cout=1uF, Iout=120mA 100 mV/ div 20mA/ div 100 mV/ div
Typical Waveforms
Cin=C2=C3=Cout=1uF, Iout=120mA
Vout
Vout
Iin
20mA/ div
Iin
50mV/ div 1.0x mode 1us/div
Vin
50mV/ div 1.5x mode 1us/div
Vin
Startup
Cin=C2=C3=Cout=1uF, Iout=120mA
25
LED Current vs. Vin
LED Current (mA)
1V/ div
EN
20
200mA/ div 2V/ div .5ms/div
15
Iin
10
Vout
5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Input Voltage (V)
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PRELIMINARY CM9142
Functional Block Diagram
C1P C1N C2P C2N
VIN
OSC 500 kHz
Charge Pump x1, x1.5
VOUT
UVLO
Bandgap
LED1
Mode Select
LED2 Current Sinks LED3 LED4 LED5 LED6
EN
Failed LED Condition
CM9142
GND ISET1 ISET2
Pin Descriptions
PIN DESCRIPTIONS
LEAD(s) NAME DESCRIPTION
1 2 3
LED1 C1P VIN
Cathode of LED1 pin. This pin is the plus side of charge pump bucket capacitor C1. Connect a 1.0F ceramic capacitor with a voltage rating of 10V or greater between C1N and C1P. Positive supply voltage input pin. This voltage should be between 2.9V and 6V. This pin requires a 1.0F or larger ceramic capacitor to ground. Current set and shutdown pin for drivers, active low.Pull high to shutdown the group. To set the LED current, a resistor, RSET, is connected between this pin and ground. The regulated LED current is 1000x the current flowing in RSET, and is
4
ISET1
approximately:
0.66V - ( LogicLow ) I LED = ---------------------------------------------------- x 1000 R SET
If this resistor is tied to directly ground (and enable function not used) Logic Low = 0, otherwise subtract the voltage drop of the device that drives this pin low.
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PRELIMINARY CM9142
Pin Descriptions (cont'd)
PIN DESCRIPTIONS
Current set and shutdown pin for drivers, active low.Pull high to shutdown the group. To set the LED current, a resistor, RSET, is connected between this pin and ground. The regulated LED current is 1000x the current flowing in RSET, and is 5 ISET2 approximately:
0.66V - ( LogicLow ) I LED = ---------------------------------------------------- x 1000 R SET
If this resistor is tied to directly ground (and enable function not used) Logic Low = 0, otherwise subtract the voltage drop of the device that drives this pin low. 6 7 8 9 10 11 12 13 14 15 16 NC NC C2N EN GND C1N LED4 C2P LED3 VOUT LED2 Cathode of LED5 pin. Cathode of LED6 pin. This pin is the minus side of charge pump bucket capacitor C2. Connect a 1.0F ceramic capacitor between C2N and C2P. PWM/Analog input pin. Can be used as second Enable pin, active high. Should tied high when not used. Ground terminal pin. This pin is the minus side of charge pump bucket capacitor C1. Connect a 1.0F ceramic capacitor between C1N and C1P. Cathode of LED4 pin. This pin is the plus side of charge pump bucket capacitor C2. Connect a 1.0F ceramic capacitor between C2N and C2P. Cathode of LED3 pin. Charge pump output voltage pin, which connects to the anodes of all LEDs. A 1F capacitor to ground is recommended. Cathode of LED2 pin.
Application Information
The CM9142 is a switched capacitor, charge pump voltage converter ideally suited for driving white LEDs to backlight LCD color displays in portable devices. The CM9142 charge pump is the perfect driver for portable applications such as cellular phones, digital still cameras, PDAs and any application where small space, compact overall size, low system cost and minimal EMI are critical. The CM9142 requires only two external switched (bucket) capacitors, plus an input and an output capac(c) 2006 California Micro Devices Corp. All rights reserved.
itor, providing for a compact, low profile design. In many applications, these can all be conveniently the same value of 1.0F, available in a compact 0805 surface mount package. The adaptive conversion ratio selects the most efficient operating mode. When VIN is higher than the needed VOUT (VLED+VCURRENT_SINK), the 1x mode is set. When the input voltage is below the LED forward voltage and a voltage boost is needed, the 1.5x mode is automatically selected. The 1.5x mode uses a frac-
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PRELIMINARY CM9142
Application Information (cont'd)
tional charge pump to convert the nominal Li-ion battery voltage (3.6V) by 1.5 times and regulates the LED current to the low dropout current sources. The current regulated sources maintain constant LED drive in the presence of supply voltage fluctuations. All LEDs are driven with the same current, even when they have slightly different forward voltages. The individual current sources sense the current through each LED and match this current to less than 2% for uniform brightness across the color LCD display. The CM9142 drives up to four WLEDS in group one and two WLEDs in the second group. The maximum current programmed by RSET determines the maximum intensity of each group's display; the displays can be further dimmed by PWM control applied to its ISET1 or ISET 2 pin.
C1 1/2 VIN
VOUT
COUT
VIN
C2 1/2 VIN
Charge C1 and C2 to 1/2 VIN each VOUT
C1 COUT
CM9142 Operation
When a voltage that exceeds the undervoltage lockout threshold (UVLO) is applied to the VIN pin, the CM9142 initiates a softstart cycle, typically lasting 100S. Softstart limits the inrush current while the output capacitors are charged. Following softstart, the CM9142 next determines the best conversion ratio (1x or 1.5x). The 1.5x mode employs a fractional charge pump. The charge pump uses two phases from the internal oscillator to drive switches that are connected to the bucket capacitors, C1 and C2, as shown in Figure 1. In the first switch position, the bucket capacitors are connected in series and each are charged from Vin to a voltage of VIN/2. The next phase changes the switch positions so that C1 and C2 are in parallel, and places them on top of VIN. The resulting voltage across COUT is then; VIN+1/2VIN = 1.5 x VIN.
VIN
1/2 VIN
C2 1/2 VIN
Transfer 1/2 VIN charge to top of VIN
Figure 1. Switch Operation
The CM9142 has over-temperature and over-current protection circuitry to limit device stress and failure during short circuit conditions. An overcurrent condition will limit the output current (approximately 400~600mA) and will cause the output voltage to drop, until automatically resetting after removal of the excessive current. Over-temperature protection disables the IC when the junction is about 135C, and automatically turns on the IC when the junction temperature drops by approximately 15C.
Efficiency
A conventional charge pump with a fixed gain of 2x will usually develop more voltage than is needed to drive paralleled white LEDs from Li-Ion sources. This excessive gain develops a higher internal voltage, reducing
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PRELIMINARY CM9142
Application Information (cont'd)
the system efficiency and increasing battery drain in portable devices. A fractional charge pump with a gain of 1.5x is better suited for driving white LEDs in these applications.
Efficiency (%) VLED=3.5V
90 1X 75 60 45
The CM9142 charge pump automatically switches between the two conversion gains, 1x and 1.5x, allowing high efficiency levels over a wide operating input voltage range. The 1x mode allows the voltage to pass directly through to the output when sufficient input voltage is available. As the battery discharges to the point where any one current source no longer has sufficient voltage headroom to maintain a constant current regulation, the 1.5x charge pump is enabled. At nominal loads, the switching losses and quiescent current are negligible. If these losses are ignored for simplicity, the efficiency, , for an ideal 1.5x charge pump can be expressed as the output power divided by the input power:
P LED = -----------P IN
1X-1.5X dual mode
2X
30 3.0 3.5 4.0 4.5
1.5X
5.0
5.5
6.0
Input Voltage (V)
Figure 2. Ideal charge pump efficiency
For an ideal 1.5x charge pump, IIN 1.5 x IOUT, and the efficiency may be expressed as;
VOUT = ( VLED + VCURRENT _ SINK ) PLED ( VOUT ) x IOUT V x 1.5 x I PIN OUT IN VOUT = 1.5 x V IN 3.9 V 1.5 x VIN
As can be seen, the CM9142, with 1x and 1.5x modes, has better efficiency in this application than a fixed 2x charge pump. At low battery voltages, the higher efficiency of the CM9142 charge pump's 1,5x gain reduces the battery drain. At higher input voltages, typically seen when the system is running off an AC adapter, the CM9142, operating the 1x mode, has better efficiency than single mode 1.5x or 2x charge pumps, lowering the power dissipation for cooler circuit operation and long life. While the charge pump efficiency is easily determined, the system efficiency is more difficult due to the current source outputs, which complicate measuring the output power. The forward voltage of the white LEDs will vary, and the constant current sources will adjust to maintain the current. When comparing systems, it is best to compare the input current for a specified LED drive current. The 1x mode has better efficiency than the 1.5x mode. Selecting LEDs with low forward voltage (VLED) increases the time spent in the 1x mode as the battery discharges, extending the operating time.
For ( VLED + VCURRENT _ SINK ) = 3.9 V,
Many charge pumps are fixed 2x designs. The ideal 2x charge pump efficiency can be similarly expressed;
P OUT 3.9V ------------- ---------------------P IN 2.0 x V IN
In 1x mode, when the input voltage is above the output voltage, the ideal efficiency is simply VOUT/VIN. The typical conversion efficiency plots for these modes, with some losses, are shown in Figure 2.
Failed LED Detection
If a LED is shorted, the CM9142 will continue to operate and drive the remaining LEDs at the programmed current. If a LED opens, the other LEDs will still be regulated at the programmed current.
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PRELIMINARY CM9142
Application Information (cont'd)
LED Current Set (ISET)
An external resistor programs a reference current, setting the maximum driver current. This resistor must be tied to a good analog ground. If it is pulled to ground through a switch, for example, from the host controller output, the voltage drop across that switch should not exceed 10mV. The voltage at the ISET1 and ISET2 pins is provided by a .66V bandgap reference. The LED current is approximately 1000x the current set by the RSET resistor, according to the following formula:
0.66V - ( LogicLow ) R SET = ---------------------------------------------------- x 1000 I LED Relative Luminous Intensity
1.5
Normalized to 20mA
1.0
0.5
0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0
Forward Current (mA)
Logic Low is the voltage on device driving this pin to ground. If the resistor is tied to ground directly, Logic low = 0. For 20mA LED current, RSET33 k. When this pin is driven high or open, the device will enter a sleep mode with VOUT = 4.5V and, with no load, IQUIESCENT 500A.
Figure 3. Typical Luminous Intensity vs. LED Current
Analog Control of Display Intensity
Typically, portable devices control the backlight display intensity in response to ambient light conditions, or lower the intensity after a short standby interval to converse battery charge. The luminous intensity of white LEDs is proportional to the amount of forward current through them, but the color wavelength emitted is also dependent upon the forward current. In applications where color shift is not critical, brightness can be controlled by adjusting the diode's current. A typical white LED Intensity vs. forward current curve is shown in Figure 3.
The ISET pins of the CM9142 can be used to connect an analog DC signal for analog dimming of the white LEDs, as shown in Figure 4 This requires an additional resistor, R, and a DC source voltage, Vc.
VC CM9142 R ISET(1,2) RSET
Figure 4. Analog LED current adjust
A control voltage, VC, applied to the resistor divider will decrease the current for all LEDs. The maximum LED current occurs with 0V on VC, which is set by RP is the parallel combination of R and RSET.
0.66V R P = ---------------------- x 1000 I LED max
Choose the maximum control voltage, VC, which sets zero LED current, and than determine the resistor ratio.
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PRELIMINARY CM9142
Application Information (cont'd)
0.66V Ratio = ------------------------Vc - 0.66 V
CM9142 ISET(1,2) RSET R 55k 82.5k Open Drain Controller Output
The resistors can be determined from the equations below.
R = ( R x Ratio ) + Rp -----------------------------------------Ratio Rset = Ratio x R
Figure 6. Logic Signal Dimming
For example, a VC max of 2.5V and a maximum current setting of 20mA, R=125k, RSET=44.8k. Figure 5 shows the control curve.
LED Current vs. Vc
25
For example, to reduce the luminosity intensity by half, using the LED curve from Figure 3, the current setting needs to be changed from 20mA to about 8mA. The values in Figure 6 will accomplish this, are where obtained using the following equations;
LED Current (mA)
20 15 10 5 0 0.0 0.5 1.0 1.5 2.0 2.5
Rp =
.66 V * 1000 ILED (max) 1 1 1 - Rp Rset
Rset =
.66 V * 1000 ILED (min)
R=
Additional parallel resistors can be added in the same way.
Control Voltage, Vc
PWM Control of Display Intensity
Typically, portable devices control the backlight display intensity in response to ambient light conditions, or lower the intensity after a short standby interval to converse battery charge. The CM9142 allows the output to lower the LED brightness by applying a pulsing (PWM) signal to EN, as shown in Figure 7 for group 2. The waveforms are shown in Figure 8. The white in white LEDs is typically bichromatic, produced by a blue or UV LED that excites yellow phosphors. The two colors combine and the human eye sees these them as white light. The forward current of the LED influences the chromaticity, with higher LED current increasing the blue content of the color. Using a PWM signal allows the LEDs to be dimmed without substantially shifting their color balance due to chromaticity shifts related to changing white LED forward current. The PWM signal causes the LEDs to
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Figure 5. LED Current Control Curve
The circuit in Figure 6 is an example of logic dimming control, which changes the LED forward current in discrete steps. The NMOS source is an open drain (or open collector if bipolar) device, either the output of a host controller, or a discrete device. Open drain, or open collector devices sink current in their active, low voltage state (logic 0), and are high impedance in their high voltage, non-active state (logic 1). The open drain must not be pulled high with an external resistor, but instead connected only to the current setting resistors. The parallel combination of R and RSET determine the full intensity current. When the drain goes high, RSET determines the lower intensity current.
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PRELIMINARY CM9142
Application Information (cont'd)
operate either at the full ISET current, or at zero current. Only the time averaged current changes. Above a minimum frequency, the human eye will perceive the change in duty cycle as a change in brightness.
VBATT
off on
VBATT
on off
VIN ISET2
VOUT Display Group1
PWM PWM
on
VIN ISET2 ISET1
on
RSET2 RSET1
VOUT LED1 LED2 LED3 LED4 Display Group1
off
LED1 LED2 LED3 LED4 ISET1 CM9142 EN GND LED5 LED6
PWM Group2
RSET2 RSET1
Enable
off
Display Group2
Group1
on off
CM9142 EN GND LED5 LED6 Display Group2
Enable
Figure 9. Separate PWM signals for each group
CM9142 Design Examples
Two Display Cell Phone
Typically, the mobile phone LCD displays (both STN and mini-TFT) require three to four white LEDs for backlighting, but as few as two of the newer highbrightness LEDs can be used. Light guides are used to distribute the light uniformly behind the LCD. In this application, four white LEDs are used for the larger main display (inside the clamshell) and two for the subdisplay. A typical application for the CM9142 is a dual display clamshell phone, with an internal main display and an external sub-display typically used for caller ID and time of day, backlighting only when there is an incoming call. When the clamshell is opened, the sub-display backlight goes off and the main display backlight goes on. See Figure 10. Either display's intensity can be lowered by a PWM signal applied to RSET resistors for the host controller, as determine by ambient light conditions.
on off
Figure 7. PWM applied to Display 2
The recommended frequency is between 100 Hz and 200 Hz, with a duty cycle greater than 20%. If a frequency of less then 100 Hz is used, flicker might be seen in the LEDs. The frequency should also be greater than the refresh rate of the TFT display. Higher frequencies will cause a loss of brightness control linearity. In addition, higher frequency can cause chromaticity shifts because the fixed rise and fall times of the PWM signal will shift the forward current. The PWM signal will cause the average LED current to be reduced. The average current is determined by the PWM duty cycle, which can vary from 0% to 100%. Decreased Duty Cycle will linearly lower LED brightness, 0% Duty Cycle will turn off the display LEDs.
EN
PWM signal
PWM
VBATT VIN
RSET2
or Analog Enable Display 1
ISET2 ISET1
VOUT LED1 LED2 LED3 LED4 LED5 LED6 Main Display
MENU
VOUT
on off
RSET1 on off
ILED (1,2,3)
ISET
Enable
CM9142 EN GND Sub Display
Caller ID
Figure 8. PWM Signal Dimming
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Figure 10. Clamshell Phone Application
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PRELIMINARY CM9142
Application Information (cont'd)
Phone with Keyboard Backlight
The CM9142 can support a wireless phone with LCD and a backlit keyboard. Group one can drive the backlight to the LCD, and group two drive the keyboard backlight. Each group can have a different current setting, and individual PWM signals applied. One or both groups can have their brightness controlled by a PWM signal. In the example in Figure 11, both are controlled with one PWM signal.
V BATT VIN RSET2 RSET1
on off
Camera Flash
The CM9142 can support a camera flash and a display in digital still cameras as well as in camera equipped smart phones and PDAs. A typical example would be the main display is supplied by group 2, and the outputs of group 1 are used to support flash white LEDs. See Figure 13. If less current is required for the Main display drivers in group two, it can be allocated to group one with the appropriate programming of the RSET resistors.
Enable Display 1 VBATT VIN ISET2 ISET1
VOUT LED1 LED2 LED3 LED4 Main Display
MENU
on off
ISET2 ISET1
VOUT LED1 LED2 LED3 LED4 LED5 LED6 WLED Flash
RSET2 Flash RSET1
CM9142 EN GND LED5 LED6
PWM
CM9142 EN GND Main Display
on off
Enable
Figure 11. Phone with Keyboard Backlight Figure 13. Display and Flash Application
PDA Backlight
The CM9142 can support larger displays such as color LCDs for PDAs by utilizing both groups. Typically, larger displays will require four or more WLED backlights. With all the drivers set at the same current, uniform backlighting can be achieved. EN can be used for ON/OFF control PWM dimming. Figure 12 shows a typical application.
V BATT
If a full regulated flash current is needed, both display outputs can be used to drive flash modules, as shown in Figure 14. In this case, EN controls the flash, enabling both outputs.
VBATT RSET2 VIN ISET2 ISET1
VOUT LED1 LED2 LED3 LED4 LED5 LED6 WLED Flash
VIN ISET2 ISET1
VOUT LED1 LED2 LED3 LED4 LED5 LED6
RSET1 Flash
CM9142 EN GND
RSET2 RSET1
on off
CM9142 EN GND
PDA Display
PWM
Figure 14. All Flash Another option, which provides the maximum flash current, can be implemented by pulling the cathode of the flash LED to ground with a switch for the brief duration of the flash. The example shown in Figure 15 shows an example that allows the flash LED to be used as a
Figure 12. PDA Display Backlight
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PRELIMINARY CM9142
Application Information (cont'd)
torch light or a preview light in normal operation, and for full flash when the external switch is turned on. In this example, the main display intensity is controlled by two line inputs to ISET1, and the torch light is controlled by S1.
VBATT VIN
EN2 EN1 66K 33K 15K RSET2 S1
For a given output current, increasing the output capacitance reduces output ripple in the 1.5x mode. Increasing the output capacitor will also increase startup current and time. In most LED applications, high frequency output ripple is not a concern because it will not cause intensity variations that are visible to the human eye.
VOUT Main Display
MENU Flash/Torch
Layout Guide
The charge pump is rapidly charging and discharging the external capacitors, so external traces to the capacitors should be made wide and short to minimize inductance and high frequency ringing. The four capacitors should be located as close as practical to the charge pump, particularly C1 and C2, which have the highest dv/dt. Use a solid ground plane, and connect the ground side of CIN, COUT and the package GND as close as practical.
LED1 LED2 LED3 LED4 CM9142 ISET2 LED5 LED6 GND ISET1
Photo Flash
Figure 15. Display, Torch and Full Flash
Capacitor Selection
For proper performance, use surface-mount, low ESR ceramic capacitors for all four positions. X7R or X5R ceramic dielectric provides good stability over the operating temperature and voltage range, The capacitance and ESR of the external bucket capacitors will directly affect the output impedance and efficiency of the converter. A ceramic 1F capacitor is recommended. Reflected input ripple depends on the impedance of the VIN source, such as the PCB traces and the Li-ion battery, which have elevated impedance at higher frequencies. The input capacitor located near the converter input reduces this source impedance and ripple. Any ESR from the capacitor will result in steps and spikes in the ripple waveform, and possibly produce EMI. Much of the ripple voltage is due to moving current charge in and out of the capacitor and the capacitor's impedance at the charge pump frequency. If ripple voltage or current on the battery bus is an application issue, add a small input inductor between the battery and the capacitor, or just increase the capacitor.
(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
13
PRELIMINARY CM9142
Mechanical Details
TQFN-16 Mechanical Specifications The CM9142 is supplied in a 16-lead, 4.0mm x 4.0mm TQFN package. Dimensions are presented below. For complete information on the TQFN16, see the California Micro Devices TQFN Package Information document. Mechanical Package Diagrams
D
PACKAGE DIMENSIONS
Leads Dim. A A1 A3 b D D1 D2 E E1 E2 e L # per tube # per tape and reel 0.55 2.05 0.65 TYP. 0.65 0.022 xx pieces* xxxx pieces
E2
16 Millimeters Min 0.00 0.20 REF 0.25 4.0 BSC 1.95 REF 2.05 4.0 BSC 1.95 REF 2.15 0.081 0.026 0.026
D1
E
Package
TQFN-16 (4x4) Inches Max 0.84 0.04 0.33 0.00 .008 0.010 0.157 0.077 2.15 0.081 0.157 0.077 0.085 0.085 0.013 Min Nom 0.031 Max 0.033 0.002
Pin 1 Marking
Nom 0.80
0.15 C 0.15 C
TOP VIEW
0.10 C
0.08 C
SIDE VIEW
A3 A1
A
Controlling dimension: millimeters
* This is an approximate number which may vary.
E1
D2 L
DAP SIZE 1.8 X 1.8
e
b
16X 0.10
M
CAB
BOTTOM VIEW
Package Dimensions for 16-Lead TQFN
(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
14

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