CALMIRCO CM9142-01QE

PRELIMINARY
CM9142
Two Group, 4 and 2, WLED Driver, Different Current Settings
Features
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.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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 10μA 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
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 10μA.
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.
Applications
•
•
•
•
Drive white LEDs for STN/TFT Color LCD backlighting
Cell phones, PDAs, with multiple displays
Digital Still Cameras
Flash for DSC
Typical Application
The CM9142 is available in a compact 16 lead TQFN
package. It can operate over the industrial temperature
range of -40°C to 85°C.
1.0uF
2.9V to 6.0V
1.0uF
C1P C1N
C2P
VIN
VOUT
1uF
off
on
Enable
RSET2
1uF
Display 1
LED1
EN
PhotonICTMLED2
CM9142
LED3
LED4
ISET1
RSET1
C2N
LED5
ISET2
GND
LED6
Display 2
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
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1
PRELIMINARY
CM9142
Package Pinout
PACKAGE / PINOUT DIAGRAM
7 LED6
8 C2N
11 C1N
14
13
12 LED4
C2P
1
LED3
2
LED1
10 GND
15
C1P
9 EN
TQFN16
4X4
16
3
LED2
4
VIN
VOUT
ISET1
6 LED5
5 SET2
Bottom View
16-Lead TQFN Package
(4mm x 4mm)
Note: This drawing is not to scale.
Ordering Information
PART NUMBERING INFORMATION
Lead-free Finish
Leads
Package
Ordering Part Number1
16
TQFN
CM9142-01QE
Part Marking
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
Specifications
ABSOLUTE MAXIMUM RATINGS
PARAMETER
RATING
UNITS
±2
kV
[GND - 0.3] to +6.0
[GND - 0.3] to +7.0
[GND - 0.3] to +5.0
[GND - 0.3] to +5.0
V
V
V
Storage Temperature Range
-65 to +150
°C
Operating Temperature Range
-40 to +85
°C
300
°C
ESD Protection (HBM)
Pin Voltages
VIN to GND
VOUT to GND
ISET1, ISET2, EN to GND
All other pins to GND
Lead Temperature (Soldering, 10s)
© 2006 California Micro Devices Corp. All rights reserved.
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490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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PRELIMINARY
CM9142
Specifications (cont’d)
ELECTRICAL OPERATING CHARACTERISTICS
VIN = 3.6V; All outputs are on. Typical values are at TA = 25°C.
SYMBOL
PARAMETER
CONDITIONS
MIN
VIN
Supply Voltage Range
VUVLO
Undervoltage Lockout
All outputs are no load.
IQ
Quiescent Current
1x mode
ISD
Shutdown Supply Current
VEN < 0.4V
2.9
VOUT Charge Pump
Output Voltage
VOUT
ILED TOT
TYP
1.7
1.8
6.0
UNIT
S
V
1.9
V
10
μA
5.5
V
300
mA
MAX
μA
500
2
4.2
IOUT = 0mA to 120mA,
VIN = 3.0 to 5.5V
Total ILED Current
Σ ILED1 thru ILED4+photoflash
Accuracy of ISET
VIN = 3.0V to 5.5V
1
Matching current between LED1
to LED6
ILED per driver
VIN = 4.0V, ILED 1 to ILED6= 20mA
2
ILED
EN, ISET
VIH
High Level Input Voltage
VIL
Low Level Input Voltage
Device total ILED < 300mA
%
5
%
50
mA
1.8
0.4
Protection
Over-current Limit
Over-temperature Limit
Over-temperature Hysteresis
400
135
15
mA
°C
°C
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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3
PRELIMINARY
CM9142
Typical Performance Curves
Charge Pump Efficiency
Source Current
Vled=3.2V
Input Current (mA)
Efficiency (%)
90
80
Iout=120mA
Iout=30mA
70
Iout=60mA
60
3.0
Vled=3.2V
200
100
3.5
4.0
4.5
5.0
5.5
175
150
Iout=120mA
125
100
75
Iout=60mA
50
Iout=30mA
25
3.0
6.0
3.5
Input Voltage (V)
4.0
4.5
5.0
5.5
Input Voltage (V)
Typical Waveforms
Typical Waveforms
Cin=C2=C3=Cout=1uF, Iout=120mA
Cin=C2=C3=Cout=1uF, Iout=120mA
100 mV/
div
Vout
20mA/
div
Iin
50mV/
div
Vin
1.0x mode
6.0
100 mV/
div
Vout
20mA/
div
Iin
50mV/
div
Vin
1us/div
1.5x mode
1us/div
LED Current vs. Vin
Startup
Cin=C2=C3=Cout=1uF, Iout=120mA
1V/
div
EN
200mA/
div
Iin
2V/
div
Vout
LED Current (mA)
25
20
15
10
5
3.0
.5ms/div
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
© 2006 California Micro Devices Corp. All rights reserved.
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490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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04/26/06
PRELIMINARY
CM9142
Functional Block Diagram
C1P C1N
C2P C2N
Charge Pump x1, x1.5
VIN
OSC
500 kHz
UVLO
VOUT
Bandgap
LED1
LED2
Mode Select
Current
Sinks
Failed LED
Condition
EN
LED3
LED4
LED5
LED6
CM9142
GND
ISET1
ISET2
Pin Descriptions
PIN DESCRIPTIONS
LEAD(s)
NAME
DESCRIPTION
1
LED1
Cathode of LED1 pin.
2
C1P
This pin is the plus side of charge pump bucket capacitor C1. Connect a 1.0μF
ceramic capacitor with a voltage rating of 10V or greater between C1N and C1P.
3
VIN
Positive supply voltage input pin. This voltage should be between 2.9V and 6V.
This pin requires a 1.0μF 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 = ----------------------------------------------------- × 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.
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
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5
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 = ----------------------------------------------------- × 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
NC
Cathode of LED5 pin.
7
NC
Cathode of LED6 pin.
8
C2N
This pin is the minus side of charge pump bucket capacitor C2. Connect a 1.0μF
ceramic capacitor between C2N and C2P.
9
EN
10
GND
Ground terminal pin.
11
C1N
This pin is the minus side of charge pump bucket capacitor C1. Connect a 1.0μF
ceramic capacitor between C1N and C1P.
12
LED4
Cathode of LED4 pin.
13
C2P
This pin is the plus side of charge pump bucket capacitor C2. Connect a 1.0μF
ceramic capacitor between C2N and C2P.
14
LED3
Cathode of LED3 pin.
15
VOUT
Charge pump output voltage pin, which connects to the anodes of all LEDs. A 1μF
capacitor to ground is recommended.
16
LED2
Cathode of LED2 pin.
PWM/Analog input pin. Can be used as second Enable pin, active high. Should tied
high when not used.
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-
itor, providing for a compact, low profile design. In
many applications, these can all be conveniently the
same value of 1.0µF, 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-
© 2006 California Micro Devices Corp. All rights reserved.
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490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
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04/26/06
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.
VOUT
COUT
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.
C1
½ VIN
VIN
C2
½ VIN
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.
Charge C1 and C2 to ½ VIN each
VOUT
C1
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
100μS. 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.
COUT
½ VIN
VIN
C2
½ VIN
Transfer ½ 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 135°C, and automatically turns on the
IC when the junction temperature drops by approximately 15°C.
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
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
l
www.cmd.com
7
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.
VLED=3.5V
90
Efficiency (%)
1X
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, η, for an ideal 1.5x charge
pump can be expressed as the output power divided by
the input power:
P LED
η = -----------P IN
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 ) × IOUT
≈ ⎜⎜
PIN
⎝ VIN × 1.5 × IOUT
⎞
VOUT
⎟⎟ =
1
.
5 × VIN
⎠
For ( VLED + VCURRENT _ SINK ) = 3.9 V,
η≈
3.9 V
1.5 × VIN
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 × 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.
75
1X-1.5X
dual mode
60
45
1.5X
2X
30
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
Figure 2. Ideal charge pump efficiency
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.
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.
© 2006 California Micro Devices Corp. All rights reserved.
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490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
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04/26/06
PRELIMINARY
CM9142
Application Information (cont’d)
LED Current Set (ISET)
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:
Relative Luminous Intensity
1.5
Normalized to 20mA
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.
1.0
0.5
0.0
0.66V – ( LogicLow )
R SET = ----------------------------------------------------- × 1000
I LED
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, RSET≅33 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≅ 500μA.
Analog Control of Display Intensity
Figure 3. Typical Luminous Intensity vs.
LED Current
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
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.
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 = ----------------------- × 1000
I LED max
Choose the maximum control voltage, VC, which sets
zero LED current, and than determine the resistor ratio.
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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PRELIMINARY
CM9142
Application Information (cont’d)
0.66V Ratio = ------------------------Vc – 0.66 V
CM9142
The resistors can be determined from the equations
below.
R
ISET(1,2)
55k
R × Ratio ) + RpR = (-----------------------------------------Ratio
82.5k
Rset = Ratio × R
Open Drain
Controller
Output
RSET
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
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)
25
Rp =
20
.66 V * 1000
ILED (max)
Rset =
.66 V * 1000
ILED (min)
15
R=
10
1
1
1
−
Rp Rset
5
Additional parallel resistors can be added in the same
way.
0
0.0
0.5
1.0
1.5
2.0
2.5
Control Voltage, Vc
PWM Control of Display Intensity
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.
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
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
l
www.cmd.com
10
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
PWM Group2
RSET2
on
off
PWM
on
VIN
VOUT
ISET2
RSET1
Enable
on
off
ISET1
Group1
VBATT
PWM
off
LED1
LED2
LED3
LED4
on
Display
Group1
RSET2
RSET1
Enable
VIN
VOUT
ISET2
LED1
LED2
LED3
LED4
ISET1
CM9142
EN
off
LED5
LED6
GND
Display
Group1
Display
Group2
CM9142
EN
LED5
LED6
Display
Group2
GND
Figure 9. Separate PWM signals for each group
CM9142 Design Examples
Two Display Cell Phone
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.
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
EN
VIN
or
Analog
PWM signal
VOUT
on
Enable
Display 1
RSET2
RSET1
off
ILED (1,2,3)
VBATT
PWM
off
ISET
on
off
Enable
VOUT
ISET2
LED1
LED2
LED3
LED4
ISET1
Main
Display
MENU
CM9142
EN
LED5
LED6
GND
Sub
Display
Caller ID
Figure 10. Clamshell Phone Application
Figure 8. PWM Signal Dimming
© 2006 California Micro Devices Corp. All rights reserved.
04/26/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
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Fax: 408.263.7846
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11
PRELIMINARY
CM9142
Application Information (cont’d)
Phone with Keyboard Backlight
Camera Flash
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.
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.
V BATT
RSET2
RSET1
on
off
PWM
VIN
VOUT
ISET2
LED1
LED2
LED3
LED4
ISET1
Main
Display
MENU
Enable
Display 1
on
RSET2
off
CM9142
EN
GND
VBATT
Flash
LED5
LED6
on
RSET1
Enable
VIN
VOUT
ISET2
LED1
LED2
LED3
LED4
ISET1
CM9142
LED5
LED6
EN
off
WLED
Flash
GND
Main
Display
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
RSET2
RSET1
on
off
PWM
VIN
VOUT
ISET2
LED1
LED2
LED3
LED4
ISET1
CM9142
EN
GND
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
RSET1
Flash
PDA
Display
VIN
VOUT
ISET2
ISET1
LED1
LED2
LED3
LED4
WLED
Flash
CM9142
EN
LED5
LED6
GND
LED5
LED6
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
© 2006 California Micro Devices Corp. All rights reserved.
12 490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
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Fax: 408.263.7846
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www.cmd.com
04/26/06
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
VOUT
LED1
LED2
LED3
LED4
CM9142
ISET2
LED5
LED6
GND
ISET1
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.
Layout Guide
Main
Display
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.
MENU
Flash/Torch
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 1μF 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.
© 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
Mechanical Package Diagrams
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.
D
Package
TQFN-16 (4x4)
Leads
16
Millimeters
A
A1
Nom
Max
0.80
0.84
0.00
A3
0.04
Min
0.25
Max
0.031
0.033
0.15 C
0.002
0.15 C
0.00
0.20 REF
b
Nom
.008
0.33
0.010
D
4.0 BSC
0.157
D1
1.95 REF
0.077
D2
2.05
E
2.15
E1
2.05
e
0.55
0.08 C
0.077
2.15
0.081
0.65 TYP.
L
0.085
0.157
1.95 REF
E2
0.10 C
0.081
4.0 BSC
TOP VIEW
0.013
A3 A1
SIDE VIEW
0.085
A
0.026
0.65
0.022
# per
tube
xx pieces*
# per
tape and
reel
xxxx pieces
D1
0.026
E2
Min
Pin 1 Marking
Inches
E1
Dim.
E
PACKAGE DIMENSIONS
Controlling dimension: millimeters
D2
* This is an approximate number which may vary.
L
DAP SIZE
1.8 X 1.8
b
e
16X
0.10
M
CAB
BOTTOM VIEW
Package Dimensions for 16-Lead TQFN
© 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