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PRELIMINARY CM9321 Asymmetrical High Efficiency Three Channel Boost LED/OLED Driver
Features
* * * Integrated WLED and OLED driver 2.7V to 6V input voltage range Up to 85% typical efficiency even for asymmetrical channel loads in terms of LED number, LED current and LED dropout Excellent 5 series x 2 parallel WLED drive capability (35 mA per channel) OLED channel with up to 18V/30 mA capability Independent current/voltage setting using external low power resistors for each channel (no ballast resistors) No external frequency compensation needed Low (<1%) LED output ripple voltage and current Input undervoltage lockout and output over-voltage protection 1 MHz fixed switching frequency (0.5 MHz option available) Uses small inductor and ceramic capacitors Integrated 0.3 internal power switch Disconnects LEDs during shutdown Low profile TQFN-16 package Optional RoHS compliant lead free packaing
Product Description
The CM9321 is a high frequency, three-channel inductorbased PWM boost regulator specifically designed for constant current white LED and constant voltage OLED drive applications. With a maximum 19V/140mA output capability, the circuit can drive up to 10 WLEDs (5 series x 2 parallel) and one OLED, allowing up to 35 mA per channel. With an input voltage range from 2.7V to 6.0V, it can operate from a single cell Li-Ion battery. The proprietary FlexBoostTM architecture (patent pending) provides high efficiency (typical 85%) for a wide input voltage range, even for asymmetrical channel loads in term of LED number, LED current and LED type. A standard (noninterleave) version is also available using a MODE selection pin (not availalbe fo mass production). The maximum LED current and OLED voltage for each channel is independently programmed with external low-power resistors (no ballast resistors needed). A 1 MHz constant frequency PWM saves board space, allowing small, low-cost external components which permits designers to avoid sensitive IF bands in RF applications. The output over-voltage protection circuit prevents damage in the case of a high impedance output (e.g. faulty LED). The controlled current limit circuit prevents large inductor current spikes, even at start-up. To avoid possible leakage currents the EN control pin disconnects the LEDs from ground during shutdown. The CM9321 is available in a compact TQFN-16 package. It can operate over the industrial temperature range of 40C to 85C.
* * *
* * * * * * * * *
Applications
* * * * * Drives white LED backlighting and OLED Cell phones Digital Cameras PDA, GPS, MP3 players Handheld devices
Typical Application
VIN 2.7V to 6.0V CIN 10 uF/10V
off on (by default)
L1 4.7 uH
D1 1A/20V
VOUT COUT 1 uF/16V
Enable
16 RSET 1 22K 2 3 RSET 21 20K 4 RSET 22 91K RSET 3 22K COLED 10 uF/16V
LED2 NC
15
NC
14
NC
13 VOUT 12 CH1 Channel CH2 CH3
EN
1
ISET1 LED1
PhotonICTM
CM9321
SW GND
11 10 OLED
VREF
ISET3
VSET2
MODE
LED3 VIN
9
interlv (by default) no-interlv
5
6
7
8
CREF
1 uF/6.3V
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PRELIMINARY CM9321
Package Pinout
PACKAGE / PINOUT DIAGRAM
Bottom View
6 ISET3 5 LED2 7 LED3 8 VIN
VSET2 VREF LED1 ISET1
4 3 2 1 16 15 14 13
9 MODE
TQFN16 4 X4
10 GND 11 SW 12 VOUT
NC
NC
Note: This drawing is not to scale.
16-Lead TQFN Package (4mm x 4mm)
Ordering Information
PART NUMBERING INFORMATION
Lead-free Finish Pins 16 Package TQFN Ordering Part Number1 CM9321-01DE Part Marking
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
Specifications
ABSOLUTE MAXIMUM RATINGS
PARAMETER ESD Protection (HBM) VIN to GND Pin Voltages VOUT, SW to GND LED1, LED2, LED3 to GND ISET1, VSET2, ISET3, VREF, EN to GND Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10s) RATING 2 [GND - 0.3] to +6.0 20 20 [GND - 0.3] to +5.0 -65 to +150 -40 to +85 300 UNITS kV V V V V C C C
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NC
EN
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PRELIMINARY CM9321
Specifications (cont'd)
ELECTRICAL OPERATING CHARACTERISTICS (SEE NOTE 1)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VIN = 3.6V; CIN = 10F, COUT = 1F, COLED = 1F, L1 = 4.7H, interleave mode, TA = 25C (unless otherwise specified) VIN IQ VUVLO VOVP ISD VEN Input Voltage Range Quiescent Current Undervoltage Lockout ILED < 0.6mA (each channel), nonswitching VIN Rising 2.7 1.2 2.0 19.0 2.2 19.5 10 1.0 0.2 2 1 0.80 8 2 5 3 1.180 10 2 1 0.80 1 140 VIN 50 5 300 95 500 20 1.220 20 450 --------------R SET1 1.260 50 30 5 V %/V mA V mVpp % m 20 x V VSET2 18 30 450 --------------R SET1 35 5 V V mA % % V A mA 6.0 2.0 2.4 20.0 15 V mA V V A V V mA
Output Overvoltage Protec- VOUT Rising tion Shutdown Current VEN = 0V Device Enable Threshold Device ON (by default) Device OFF VIN = 3.0V to 6.0V, RSET1(k) 4 WLED
Channel 1 (WLED) LED Current (Note 1) ILED1
Number of WLEDs (Note 2) VIN = 2.7V to 6.0V VLED1 Voltage on LED1 Pin Standard load (Note 3) VIN = 3.0V to 6.0V VIN = 2.7V to 6.0V VIN = 3.0V to 6.0V, IOLED = 5mA to 20mA 1% divider resistors TA = 25C to 85C (Recommended) VIN = 3.0V to 6.0V, RSET1(k) 4 WLED Channel 2 (OLED) VOLED OLED Voltage (Note 4) IOLED OLED Current Range
VOLED / VOLED VOLED Regulation
VOLEDacc VREF IREF OLED Voltage Accuracy Reference Voltage VREF Divider Current
Channel 3 (WLED) ILED3 LED Current (Note 1)
Number of WLEDs (Note 2) VIN = 2.7V to 6.0V VLED3 Voltage on LED3 Pin Standard load (Note 3) VIN = 3.0V to 6.0V Each Channel VIN = 3.0V to 6.0V Standard Load (Note 3) Standard Load (Note 3) VIN = 2.7V to 6.0V, ILED = 2mA to ILED MAX ISW = 0.8A, VGS = 15V Boost Circuit (Note 3) ILED / ILED VIN Line Regulation IOUT VOUT VOUTR D RDSON Boost Output Current Boost Output Voltage Output Voltage Ripple Duty Cycle Range MOSFET ON Resistance
(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
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PRELIMINARY CM9321
Specifications (cont'd)
ELECTRICAL OPERATING CHARACTERISTICS (SEE NOTE 1)
SYMBOL Eff ISW PIN Control ILED acc ILEDR ILEDNL fs PARAMETER Efficiency Switch Peak Current Input Power CONDITIONS Standard Load (Note 3) Standard Load (Note 3) ILED 1,2 = 20mA, 4WLED+OLED+2W 1% RSET Accuracy, Each Channel Standard Load (Note 3) All Channels VIN = 2.7V to 6.0V 0 0.8 1.0 MIN TYP 85 0.65 950 MAX UNITS % A mW
Channel Current Matching (Note 5) LED Current Ripple No-Load Mode (Note 5) Switching Frequency
3 0.2 0.6 1.2
% mApp mA MHz
VIN = 3.6V; CIN = 10F, COUT = 1F, COLED = 1F, L1 = 4.7H, non-interleave mode (Note 7), TA = 25C (unless otherwise specified) LED Current VIN = 3.0V to 6.0V, RSET(k) 2 IMAX mA ILED 730-----------R SET PIN Input Power ILED 1,2,3 = 20mA, 4WLED+OLED+2W
I LED ( mA ) 450 = ---------------------
990
mW
Note 1: ILED is the average PWM current through the LED string with internal 2/3 duty cycle and a 6 ms period. The following formula must be used to calculate the LED current:
R SET ( k )
Note 2: For lower LED forward voltage the number of LEDs can be increased up to the maximum output voltage limit. Note 3: Standard Load is a 4 series x 2 parallel WLEDS configured for IsetLED = 20 mA each channel (RSET1 = RSET3 = 22 k) and one OLED channel (CH2) which drives VOLED=12V and IOLED=20mA. Note 4: VVSET2, the voltage on VSET2 pin should be maintained in the 0.4V - 1.0V range. The following formulae are related to OLED channel settings:
R SET22 V OLED = V OUT - V LED , V OLED = 20 x V SET2 , V VSET2 = ------------------------------------------ x V REF R SET21 + R SET22
Note 5: [ILED(set) - ILED(effective)]/ILED(set) for each channel. Note 6: A ILED value below 0.6 mA for each channel set the circuit in no-load mode; all channels and MOSFET switch are in shutdown and DC circuit current consumption is limited to 1 mA (see quiescent current). Note 7: For non-interleave mode, all parameters have the same min/typ/max interleave mode values, unless otherwise specified.
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PRELIMINARY CM9321
Typical Performance Curves
ILED vs. VIN
21 .2 21 .0 20.8 20.6 1 6
VOLED vs. VIN
ILED1
1 4
VOLED 12V
1 2
ILED (mA)
20.2 20.0 1 9.8 1 9.6 1 9.4 1 9.2 1 9.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
VOLED (V)
20.4
VOLED=10V
1 0
VOLED=8.5V
ILED3 L = 4.7uH 4 WLED/ch TA = 25 C
8
6
ILED1,3 = 20mA CH1,2,3 = 4W+OLED+4W COLED = 10uF
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
4
VIN (V)
VIN (V)
EFFICIENCY v.s VIN
90 90
EFFICIENCY vs. ILED
Vin=5.6V
85
Efficiency (%)
Efficiency (%)
85
80
4.2V 3.6V 3.0V 2.7V
75
80
70
ILED1,2,3 = 20mA L = 4.7uH 4 WLED/ch
75 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
65
L = 4.7uH 4 WLED/ch TA = 25 C
0 5 1 0 1 5 20 25 30 35
60
VIN (V)
ILED (m A)
EFFICIENCY vs. INDUCTOR
90
EFFICIENCY vs. STRING CONFIGURATION
90 88 86
L=4.7uH
85
Efficiency (%)
Efficiency (%)
L=3.3uH L=2.7uH L=1.5uH
CH1,2,3=20mA+10V+20mA
80
84 82 80 78 76 74
CH1,2,3=5mA+10V+20mA CH1,2,3=20mA+10V+5mA
75
L=10uH L=15uH
70
VOLED = 10V ILED1,3 = 20 mA 4 WLED/ch TA = 25 C
4.5 5.0 5.5 6.0
L = 4.7uH CH1,2,3 = 4W+OLED+2W TA = 25 C
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
65 2.0 2.5 3.0 3.5 4.0
VIN (V)
(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
VIN (V)
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PRELIMINARY CM9321
Functional Block Diagram
VIN
EN
ENABLE UVLO BIAS PMW LOGIC
OVP OSC D4
VOUT SW
Q4 R
VREF
BG
ISET1 VSET2
CONTROL
D1
Q1
LED1
D2
LED2
Q2
ISET3
D3 Q3
LED3
MODE
CM9321
GND
Pin Descriptions
PIN DESCRIPTIONS
LEAD(s) NAME DESCRIPTION
Channel 1 LED current set pin. Between this pin and GND connect the RSET1 resistor, calculated as follows: 1 ISET1
450 R SET1 ( k ) = ---------------------------I LED1 ( mA )
where ILED1 is the DC LED current in channel 1. 2 3 4 5 LED1 VREF VSET2 LED2 Pin to cathode of channel 1 LED string. Reference voltage output pin, used to bias VSET2 node. The voltage on this pin sets the VOLED as follows:
V OLED = 20 x V SET2
Pin to cathode of channel 2 LED string.
(c) 2006 California Micro Devices Corp. All rights reserved.
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Tel: 408.263.3214
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Fax: 408.263.7846
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PRELIMINARY CM9321
Pin Descriptions (cont'd)
PIN DESCRIPTIONS
Channel 3 LED current set pin. Between this pin and GND connect the RSET3 resistor, calculated as follows: 6 ISET3
450 R SET3 ( k ) = ---------------------------I LED3 ( mA )
where ILED3 is the DC LED current in channel 3. 7 8 9 10 11 12 13 14 15 16 EPad LED3 VIN MODE GND SW VOUT EN NC NC NC GND Pin to cathode of channel 3 LED string. Input supply voltage pin. Bypass with a 10F or larger ceramic capacitor to ground. When MODE is HIGH (default), the circuit uses interleave mode. When MODE is LOW (GND), the circuit uses non-interleave mode. Ground terminal pin. Switching node. Internally connected to the drain of the integrated switch. Output voltage pin, which connects to the anodes of all LEDs. Bypass with a 1.0F or greater ceramic capacitor to ground for low output ripple voltage. Enable pin. The circuit is ON when VEN is above 1.0V. The circuit is OFF when VEN is below 0.2V. Active High (ON) by default. Not internally connected. For better heat flow, connect to GND. Not internally connected. For better heat flow, connect to GND. Not internally connected. For better heat flow, connect to GND. Ground; backside exposed pad.
Application Information
The CM9321 is a high efficiency, constant frequency current regulating boost driver ideally suited for driving white LEDs to backlight LCD color displays and a camera flash in Li-ion powered portable devices. The CM9321 is the perfect driver for portable applications such as cellular phones, digital still cameras, PDAs, and any application where small space, compact overall size, and low system cost, are critical. With a maximum 140mA/19V output capability, the circuit can drive up to 10 WLEDs (5 series x 2 parallel) allowing up to 35mA per channel. It includes a switch and an internally compensated loop for regulating the current into the LEDs. The CM9321 delivers a constant current to series-connected LEDs, ensuring uniform brightness and color purity regardless of any LED forward voltage variations. The proprietary design architecture allows asymmetrical loading on each channel and maintains high effi(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
ciency (typ 85%) at low VIN resulting in longer battery life, and cool, reliable operation when an adapter is supplying high VIN. The maximum LED current for each channel is independently programmed with external low power resistors avoiding ballast resistors. A 1MHz constant frequency PWM scheme saves board space using of small, low cost external components , allowing designers to avoid sensitive IF bands in RF applications. The circuit operates with low value inductor and low value output ceramic capacitor keeping voltage and current ripple in the 1% range. The output over-voltage protection circuit prevents damage in the case of a high impedance output (e.g. faulty LED). The controlled current limit circuit limit prevents large inductor current spikes, even at start-up. To avoid possible leakage currents the EN control pin disconnects the LEDs from ground during shutdown.
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PRELIMINARY CM9321
Application Information (cont'd)
CM9321 Operation
When a voltage that exceeds the undervoltage lockout threshold (UVLO) is applied to the VIN pin, the CM9321 initiates a softstart which limits the inrush current while the output capacitors are charged. Following softstart, the CM9321's internal NMOS drives an external inductor and Schottky diode to deliver the inductor's stored energy to the load. Setting the LED Current The output currents for channel 1 (up to 40mA) and channel 3 (up to 30 mA) are set by the value of their RSET resistor, located between the ISET(1,3) pin and GND, according to the equations:
ILED (mA)
switch transistor for positive slope. See Figure 1 for different brightness control methods and results.
PWM signal RSET1 ISET1 22k VSET2 RSET3 ISET3 91k CM9321
(a) Schematic
25
20
ILED1 negative slope
(a) Interleave (b) Non-interleave
450 R SET ( k ) = ------------------------I LED ( mA ) 730 R SET ( k ) = ------------------------I LED ( mA )
1 5
1 0
ILED3 positive slope
5
Setting the OLED Voltage The output voltage for the OLED is the difference between VOUT the voltage at ILED3 pin. The voltage is programmed using the voltage divider R22 and R21, according to the equation:
V OLED = 20 x V SET2
0 0 1 0 20 30 40 50 60 70 80 90 1 00
DUTY (%)
(b) Brightness curves
Figure 1. Brightness Control Using Different Methods Inductor Selection
PWM Brightness Control The brightness WLEDs level can be continuously controlled for each channel using a PWM signal in 1-50 KHz range (recommended value is 10 kHz). As an example the PWM signal can be applied directly through RSET resistor for negative slope or by using a
The inductor is used to store energy in a boost converter. The amount of energy stored in the inductor and transferred to the load is controlled by the PWM. The inductor is operated in the discontinuous conduction mode, and to assume proper operation, the inductor value must be limited to a maximum value. An inductor with low series resistance (DCR) decreases power losses and increases efficiency. The core material should be capable of operating at I MHz with minimum core losses. An inductance of 4.7-H is optimal for most applications, but low DCR inductor values in 1.5-15uH range are also recommended for high efficiency applications. To ensure proper operation of the current regulator over a wide range of conditions, the inductor should be selected based on the required load power and the minimum input voltage. The saturation current rating
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PRELIMINARY CM9321
Application Information (cont'd)
should be chosen well above the steady state peak inductor current. At minimum Vin and full duty cycle (worse case), this is approximately:
1V IN ( MIN ) x t ON 3V x 0.95 x --------------1MHz I PEAK -------------------------------------- ---------------------------------------------- 0.7A L 4.7H
In this case, because of small input ripple, the efficiency is about 2% higher.
to V IN
CM9321
LED3
GND
10
interlv (by default) non-interlv
VIN
Diode Selection The low forward voltage and fast switching time make Schottky diodes the choice for high efficiency operation. Make sure the diode has a reverse voltage rating greater than the maximum output voltage. The diode conducts only when the power switch is on, so a peak current rating above 1A should be sufficient for a typical design. Capacitor Selection For proper performance, use surface-mount, low ESR ceramic capacitors for CIN and COUT. X7R or X5R ceramic dielectric provides good stability over the operating temperature and voltage range. 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. For such applications, when low ripple is needed, a 22F input capacitor and/or 2.2 F output capacitor are recommended.
REF DES CIN COUT L1
MODE 9 8
RF 100 CF 0.1 uF/10V
7
Figure 2. Input Filter Solution
Mode Selection Two working modes are available for CM9321: interleave mode (output voltage is periodically adjusted depending on each channel load) and non-interleave mode (same output voltage level for all channels). For interleave option, keep MODE pin floating (HIGH by default) and for non-interleave option, connect MODE pin to GND.
Layout Guide
Components should be placed as close as practical to the IC to assure good performance. The input and output capacitors should be close, with minimum trace resistance and inductance. Reflected input ripple depends on the impedance of the VIN source, such as the PCB traces and the Li-ion battery, which has 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. Route any noise sensitive traces away from the switching power components. Place the inductor and diode as close as possible to the SW pin to prevent noise emissions. The ground connections for RSET(1,21,22,3) resistors should be kept separate from the high power grounds and connect directly to the ground pin to assure accurate current and voltage settings. For better heat flow, connect all NC pins to GND plane. Also connect the
DESCRIPTION Capacitor, 10F, 10V, Ceramic, 1206 Capacitor, 1F, 16V, Ceramic, 0805 Inductor, 4.7H, 1A, Low DCR
D1
Schottky Diode, 1A, 20V, SMD
SOURCE Murata, GRM319R61A106KE19D Vishay, VJ1206G106KXQ Murata, GRM188R61C105KA93D TDK, C2012X5R1C105K Coilcraft, LP06013-472ML TMP Electronics Co., SPC-03802-4R7 CHILISIN, SCD03015-4R7 SUMIDA, CDH3D13/S4R7 IR, MBRS120 CHENMKO, SSM5817S
Input Filter If CM9321 is more than 4" from main power supply point, use an input RC filter to avoid high ripple and input transients to the circuit input pin (see Figure 2).
(c) 2006 California Micro Devices Corp. All rights reserved. 04/26/06
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PRELIMINARY CM9321
Application Information (cont'd)
thermal landing to the bottom ground plane with thermal vias.
Figure 3. Example CM9321 PC Layout and Component Placement for Standard Application
(c) 2006 California Micro Devices Corp. All rights reserved.
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PRELIMINARY CM9321
Mechanical Details
TQFN-16 Mechanical Specifications The CM9321 is supplied in a 16-lead, 4.0mm x 4.0mm QFN package. Dimensions are presented below. For complete information on the QFN16, see the California Micro Devices QFN 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
QFN-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
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