2006 California Micro Devices Corp. All rights reserved.
05/08/06
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
1
CM9320
PRELIMINARY
Features
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
Up to 100 mA/19V output current/voltage
Independent current setting using an external low
power resistor for each channel (no ballast resistors)
No external frequency compensation needed
Low (<1%) LED output voltage and current ripple
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 low ON-Resistance (0.3
) N-Chann el
MOSFET switch
Disconnects LEDs during shutdown
Low profile TDFN-10 package
Optional RoHS compliant lead free packaging
Applications
Drives white LEDs for backlighting color LCD
Cell phones
MP3 players, PDA, GPS
Digital Still Cameras
LED flashlights
Handheld devices
Product Description
The CM9320 is a high frequency, two-channel inductor-
based PWM boost regulator specifically designed for con-
stant current white LED drive applications. With a maxi-
mum 100 mA/19V output capability, the circuit can drive
up to 10 WLEDs (5 series x 2 parallel) allowing up to 35
mA per channel. With a typical input voltage range from
2.7V to 6.0V, it can be operated from a single cell Li-Ion
battery.
The proprietary FlexBoost
TM architecture (patent pending)
provides high efficiency (typical 85%) for a wide input volt-
age range, even for asymmetrical channel loads in terms
of LED number, LED current and LED type. The maximum
LED current for each channel is independently pro-
grammed with external low-power resistors (no ballast
resistors needed).
A 1 MHz constant frequency PWM saves board space,
allowing small, low-cost external components, permitting
designers to avoid sensitive IF bands in RF applications.
The output over-voltage protection circuit prevents dam-
age in 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 CM9320 is available in a compact TDFN-10 package.
It can operate over the industrial temperature range of -
40C to 85C.
2.7V to 6.0V
CM9320
ISET1
GND
ISET2
VOUT
SW
LED2
EN
VIN
LED1
V
IN
3
6
7
8
9
10
L1
D1
4.7 uH
1A, 20V
V
OUT
C
OUT
R
SET1
C
IN
10 uF/10V
1 uF/16V
22K
NC
2
4
5
Enable
on (by default)
off
Channel
CH1
CH2
R
SET2
22K
1
PhotonIC
TM
Typical Application
Asymmetrical High Efficiency Two Channel Boost LED Driver
2006 California Micro Devices Corp. All rights reserved.
2
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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05/08/06
CM9320
PRELIMINARY
Ordering Information
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
Specifications
PACKAGE / PINOUT DIAGRAM
Note: This drawing is not to scale.
CM9320-01DE
10 Lead TDFN Package
CMxxx
GND
4
3
2
1
4
3
2
1
6
7
8
9
PAD
xxxxxx
7
8
9
10
6
5
5
10
Pin 1
Marking
BOTTOM VIEW
(Pins Up View)
TOP VIEW
(Pins Down View)
PART NUMBERING INFORMATION
Pins
Package
Lead Free Finish
Ordering Part Number
1
Part Marking
10
TDFN
CM9320-01DE
ABSOLUTE MAXIMUM RATINGS
PARAMETER
RATING
UNITS
ESD Protection (HBM)
2
kV
VIN to GND
[GND - 0.3] to +6.0
V
Pin Voltages
V
OUT
, SW to GND
LED1, LED2 to GND
ISET1, ISET2 to GND
20
20
[GND - 0.3] to +5.0
V
V
V
Storage Temperature Range
-65 to +150
C
Operating Temperature Range
-40 to +85
C
Lead Temperature (Soldering, 10s)
300
C
Package Pinout
2006 California Micro Devices Corp. All rights reserved.
05/08/06
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3
CM9320
PRELIMINARY
ELECTRICAL OPERATING CHARACTERISTICS
(SEE NOTE 1)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
= 3.6V; C
IN
= 10
F, C
OUT
= 1
F, L
1
= 4.7
H, interleave mode, T
A
= 25C (unless otherwise specified)
V
IN
Input Voltage Range
2.7
6.0
V
I
Q
Quiescent Current
I
LED
< 0.6mA (each channel), non-
switching
1.2
2.0
mA
V
UVLO
Undervoltage Lockout
V
IN
Rising
2.0
2.2
2.4
V
V
OVP
Output Overvoltage Protection
V
OUT
Rising
19.0
19.5
20.0
V
I
SD
Shutdown Current
V
EN
= 0V
10
15
A
V
EN
Device Enable Threshold
Device ON (by default)
Device OFF
1.0
0.2
V
V
Channel 1
I
LED1
LED Current (Note 1)
V
IN
= 3.0V to 6.0V, R
SET1
(k
)
4 WLED
2
35
mA
Number of LEDs (Note 2)
V
IN
= 2.7V to 6.0V
1
5
V
LED1
Voltage on LED1 Pin
Standard load (Note 3)
0.80
V
Channel 2
I
LED2
LED Current (Note 1)
V
IN
= 3.0V to 6.0V, R
SET2
(k
)
4 WLED
2
30
mA
Number of LEDs (Note 2)
V
IN
= 2.7V to 6.0V
1
5
V
LED2
Voltage on LED2 Pin
Standard load (Note 3)
0.80
V
Boost Circuit (Note 3)
I
LED
/ I
LED
V
IN
Line Regulation
V
IN
= 3.0V to 6.0V Each Channel
1
%/V
I
OUT
Boost Output Current
V
IN
= 3.0V to 6.0V
80
mA
V
OUT
Boost Output Voltage
I
LED 1,2
= 2mA to I
LED MAX
V
IN
20
V
D
Duty Cycle Range
V
IN
= 2.7V to 6.0V,
I
LED 1,2
= 2mA to I
LED MAX
5
95
%
V
OUTR
Output Voltage Ripple
Standard Load (Note 3)
50
mVpp
R
DSON
MOSFET ON Resistance
I
SW
= 0.8A, V
GS
= 15V
300
500
m
Eff
Efficiency
Standard Load (Note 3)
85
%
I
SW
Switch Peak Current
Standard Load (Note 3)
0.5
A
P
IN
Input Power
I
LED 1,2
= 20mA, 4WLED+1W
835
mW
Control
I
LED acc
Channel Current Matching
(Note 4)
1% R
SET
Accuracy, Each Channel
3
%
I
LEDR
LED Current Ripple
Standard Load (Note 3)
0.2
mApp
I
LEDNL
No-Load Mode (Note 5)
All Channels
0
0.6
mA
fs
Switching Frequency
V
IN
= 2.7V to 6.0V
0.8
1.0
1.2
MHz
450
R
SET1
---------------
450
R
SET2
---------------
Specifications (cont'd)
2006 California Micro Devices Corp. All rights reserved.
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CM9320
PRELIMINARY
Note 1: I
LED
is the average PWM current through the LED string with internal 2/3 duty cycle and a 6 ms period. The following for-
mula must be used to calculate the LED current:
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 configuration set for I
setLED
= 20 mA each channel (R
SET1,2
= 22 k
).
Generally, a "4W+1W" like formula denotes the WLED number of each channel, i.e. CH1+CH2 configurations.
Note 4: [I
LED
(set) - I
LED
(effective)] / I
LED
(set) for each channel.
Note 5: A LED current 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 6: For non-interleave mode, all parameters have the same min/typ/max interleave mode values, unless otherwise specified.
V
IN
= 3.6V; C
IN
= 10
F, C
OUT
= 1
F, L
1
= 4.7
H, non-interleave mode (Note 6), T
A
= 25C (unless otherwise specified)
I
LED
LED Current
V
IN
= 3.0V to 6.0V, R
SET
(k
)
2
I
MAX
mA
I
LED
/
V
IN
Line Regulation @ High Load
L = 4.7
H, V
IN
= 3.0V to 5.5V
4W+4W, 40mA+40mA
1
%/V
L = 10
H, VIN = 3.0V to 5.5V
4W+4W, 50mA+40mA
3
%/V
L = 10
H, VIN = 2.8V to 5.5V
3W+4W, 60mA+40mA
1
%/V
P
IN
Input Power
I
LED 1,2
= 20mA, 4WLED+1W
730
mW
ELECTRICAL OPERATING CHARACTERISTICS
(SEE NOTE 1)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
730
R
SET
-------------
ILED mA
(
)
450
RSET k
(
)
----------------------
=
Specifications (cont'd)
2006 California Micro Devices Corp. All rights reserved.
05/08/06
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
CM9320
PRELIMINARY
EFFICIENCY vs. INDUCTOR
65
70
75
80
85
90
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VIN (V)
E
f
fi
c
i
e
n
c
y
(%
)
ILED1,2 = 20 mA
4 WLED/ch
TA = 25 C
L=4.7uH
L=3.3uH
L=2.7uH
L=1.5uH
L=10uH
L=15uH
EFFICIENCY vs. STRING CONFIGURATION
74
76
78
80
82
84
86
88
90
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VIN (V)
E
f
f
i
c
i
en
cy
(
%
)
L = 4.7uH
CH1,2 = 4W+3W
TA = 25 C
ILED=20mA+20mA
ILED=5mA+20mA
ILED=20mA+5mA
ILED vs. VIN
19.0
19.2
19.4
19.6
19.8
20.0
20.2
20.4
20.6
20.8
21.0
21.2
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VIN (V)
IL
E
D
(
m
A
)
L = 4.7uH
4 WLED/ch
TA = 25 C
ILED2
ILED1
EFFICIENCY vs. ILED
60
65
70
75
80
85
90
0
5
10
15
20
25
30
35
ILED (mA)
E
ffi
c
i
e
n
c
y
(%
)
L = 4.7uH
4 WLED/ch
TA = 25 C
Vin=5.6V
4.2V
3.6V
3.0V
2.7V
EFFICIENCY v.s VIN
75
80
85
90
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VIN (V)
Ef
f
i
c
i
e
n
c
y
(
%
)
ILED1,2 = 20mA
L = 4.7uH
4 WLED/ch
ILED vs. VIN (high currents)
50
60
70
80
90
100
110
120
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
VIN (V)
IL
E
D
1
+
IL
E
D
2
(
m
A
)
No-Interleave
TA = 25 C
L=10uH, 3W+4W, 60mA+40mA
L=10uH, 4W+4W, 50mA+40mA
L=4.7uH, 4W+4W, 40mA+40mA
Typical Performance Curves
2006 California Micro Devices Corp. All rights reserved.
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CM9320
PRELIMINARY
Pin Descriptions
VIN
CM9320
ISET1
EN
S W
VOUT
LE D2
LE D1
ISET2
PMW
LOGIC
GND
CONTROL
OVP
Q1
Q2
Q4
D1
D2
D4
OSC
BG
UVLO
BIAS
R
ENABLE
PIN DESCRIPTIONS
LEAD(s)
NAME
DESCRIPTION
1
ISET1
Channel 1 LED current set pin. Between this pin and GND connect the R
SET1
resistor, calcu-
lated as follows:
where I
LED1
is the DC LED current in channel 1.
2
LED1
Pin to cathode of channel 1 LED string.
3
NC
Not internally connected. For better heat flow, connect to GND.
4
ISET2
Channel 2 LED current set pin. Between this pin and GND connect the R
SET2
resistor, calcu-
lated as follows:
where I
LED2
is the DC LED current in channel 2.
5
LED2
Pin to cathode of channel 2 LED string.
6
VIN
Input supply voltage pin. Bypass with a 10F or larger ceramic capacitor to ground.
7
GND
Ground terminal pin.
8
SW
Switching node. Internally connected to the drain of the integrated switch.
9
VOUT
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.
R
SET1
k
(
)
450
I
LED1
mA
(
)
-----------------------------
=
R
SET
2
k
(
)
450
I
LED
2
mA
(
)
-----------------------------
=
Functional Block Diagram
2006 California Micro Devices Corp. All rights reserved.
05/08/06
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7
CM9320
PRELIMINARY
Application Information
The CM9320 is a high efficiency, constant frequency
current regulating boost driver ideally suited for driving
white LEDs to backlight LCD color displays and a cam-
era flash in Li-ion powered portable devices. The
CM9320 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 100 mA/19V output capability, the cir-
cuit can drive up to 10 WLEDs (5 series x 2 parallel),
allowing up to 35 mA per channel. It includes a switch
and an internally compensated loop for regulating the
current into the LEDs. The CM9320 delivers a constant
current to series-connected LEDs, ensuring uniform
brightness and color purity regardless of any LED for-
ward voltage variations.
The proprietary design architecture allows asymmetri-
cal loading on each channel and maintains high effi-
ciency (typ 85%) at low V
IN
resulting in longer battery
life, and cool, reliable operation when an adapter is
supplying high V
IN
. The maximum LED current for
each channel is independently programmed with exter-
nal low power resistors avoiding the need for ballast
resistors.
An 1MHz constant frequency PWM scheme saves
board space with the use of small, low cost external
components, allowing designers to avoid sensitive IF
bands in RF applications. The circuit operates with low
value inductors and low value output ceramic capaci-
tors, keeping voltage and current ripple in the 1%
range.
The output over-voltage protection circuit prevents
damage in 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 discon-
nects the LEDs from ground during shutdown.
CM9320 Operation
When a voltage that exceeds the undervoltage lockout
threshold (UVLO) is applied to the VIN pin, the
CM9320 initiates a softstart which limits the inrush cur-
rent while the output capacitors are charged. Following
softstart, the CM9320's internal NMOS drives an exter-
nal inductor and Schottky diode that delivers the induc-
tor's stored energy to the load.
Setting the LED Current
The output current is set by the value of the R
SET
con-
nected between the I
SET
pin and GND, according to
the equations:
(a) Interleave
(b) Non-interleave
PWM Brightness Control
The brightness WLEDs level can be continuously con-
trolled 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 R
SET
resistor for negative slope or by using a
10
EN
Enable pin. The circuit is ON when V
EN
is above 1.0V. The circuit is OFF when V
EN
is below
0.2V. Active High (ON) by default.
EPad
GND
Ground (backside exposed pad).
PIN DESCRIPTIONS
R
SET
k
(
)
450
I
LED
mA
(
)
--------------------------
=
R
SET
k
(
)
730
I
LED
mA
(
)
--------------------------
=
Pin Descriptions (cont'd)
2006 California Micro Devices Corp. All rights reserved.
8
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
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Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
05/08/06
CM9320
PRELIMINARY
switch transistor for positive slope. See
Figure 1
for dif-
ferent brightness control methods and results.
Figure 1. Brightness Control Using
Different Methods
Inductor Selection
The inductor is used to store energy in a boost con-
verter. 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 4.7H is
optimal for most applications, but low DCR inductor val-
ues 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
should be chosen well above the steady state peak
inductor current. At minimum V
IN
and full duty cycle
(worse case), this is approximately:
Diode Selection
The low forward voltage and fast switching time make
Schottky diodes the choice for high efficiency opera-
tion. 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 typi-
cal design.
Capacitor Selection
For proper performance, use surface-mount, low ESR
ceramic capacitors for C
IN
and C
OUT
. X7R or X5R
ceramic dielectric provides good stability over the oper-
ating temperature and voltage range.
In most LED applications, high frequency output ripple
is not a concern because it will not cause intensity vari-
ations that are visible to the human eye.
For such applications, when low ripple is needed, a
22
F input capacitor and/or 2.2 F output capacitor are
recommended.
Input Filter
If CM9320 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
).
0
5
10
15
20
25
0
10
20
30
40
50
60
70
80
90
100
DUTY (%)
IL
E
D
(
m
A
)
ILED1
negative slope
ILED2
positive slope
CM9320
ISET1
PWM
signal
ISET2
22k
R
SET1
91k
R
SET2
(a) Schematic
(b) Brightness curves
REF
DES
DESCRIPTION
SOURCE
C
IN
Capacitor, 10
F,
10V, Ceramic, 1206
Murata, GRM319R61A106KE19D
Vishay, VJ1206G106KXQ
C
OUT
Capacitor, 1
F, 16V,
Ceramic, 0805
Murata, GRM188R61C105KA93D
TDK, C2012X5R1C105K
L
1
Inductor, 4.7
H, 1A,
Low DCR
Coilcraft, LP06013-472ML
TMP Electronics Co., SPC-03802-4R7
CHILISIN, SCD03015-4R7
SUMIDA, CDH3D13/S4R7
D
1
Schottky Diode, 1A,
20V, SMD
IR, MBRS120
CHENMKO, SSM5817S
I
PEAK
V
IN MIN
(
)
t
ON
L
---------------------------------------
3V 0.8
1
1MHz
----------------
4.7
H
-------------------------------------------- 0.5A
Application Information (cont'd)
2006 California Micro Devices Corp. All rights reserved.
05/08/06
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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9
CM9320
PRELIMINARY
In this case, because of small input ripple, the effi-
ciency is about 2% higher.
Figure 2. Input Filter Solution
Layout Guide
Components should be placed as close as practical to
the IC to assure good performance. The input and out-
put 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 have ele-
vated 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 switch-
ing power components. Place the inductor and diode
as close as possible to the SW pin to prevent noise
emissions.
The ground connections for RSET(1,2) resistors
should be kept separate from the high power grounds
and connect directly to the ground pin to assure accu-
rate current and voltage settings. For better heat flow,
connect all NC pins to GND plane. Also connect the
thermal landing to the bottom ground plane with ther-
mal vias.
Figure 3. Example CM9320 PC Layout and
Component Placement for Standard Application
CM9320
GND
VIN
6
7
C
F
0.1 uF/10V
R
F
100
V
IN
to
Application Information (cont'd)
2006 California Micro Devices Corp. All rights reserved.
10
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
l
Tel: 408.263.3214
l
Fax: 408.263.7846
l
www.cmd.com
05/08/06
CM9320
PRELIMINARY
TDFN-10 Mechanical Specifications
Dimensions for the CM9320 packaged in a 10-lead
TDFN package are presented below.
For complete information on the TDFN-10, see the Cal-
ifornia Micro Devices TDFN Package Information docu-
ment.
=
This package is compliant with JEDEC standard MO-229, variation
WEED-3 with exception of the "D2" and "E2" dimensions as called
out in the table above.
Package Dimensions for 10-Lead TDFN
PACKAGE DIMENSIONS
Package
TDFN
JEDEC
No.
MO-229 (Var. WEED-3)
=
Leads
10
Dim.
Millimeters
Inches
Min
Nom
Max
Min
Nom
Max
A
0.70
0.75
0.80
0.028
0.030
0.031
A1
0.00
0.02
0.05
0.000
0.001
0.002
A2
0.45
0.55
0.65
0.018
0.022
0.026
A3
0.20
0.008
b
0.18
0.25
0.30
0.007
0.010
0.012
D
3.00
0.118
D2
2.20
2.30
2.40
0.087
0.091
0.094
E
3.00
0.118
E2
1.40
1.50
1.60
0.055
0.060
0.063
e
0.50
0.020
K
1.30
1.50
1.70
0.051
0.060
0.067
L
0.20
0.30
0.40
0.008
0.012
0.016
# per
tube
NA
# per
tape and
reel
3000 pieces
Controlling dimension: millimeters
Mechanical Package Diagrams
BOTTOM VIEW
A
A3
A1
0.10 C
0.08 C
SIDE VIEW
TOP VIEW
b
L
0.10
C A B
M
8X
D2
E2
e
GND PAD
D
E
Pin 1
Marking
4
3
2
1
7
8
9
10
A2
K
7
8
9
10
3
2
1
4
5
6
5
6
Pin 1 ID
C0.35
Mechanical Details
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