AIC AIC1843

AIC1843
High Efficiency 1.5X charge Pump
For White LEDs Backlighting
FEATURES
GENERAL DESCRIPTION
1MHz Switching Frequency
The AIC1843 provides 4 LED current source
outputs with regulated constant current for uniform
intensity. The AIC1843 is the low noise, constant
frequency charge pump DC/DC converter that
uses 1.5X conversion to increase efficiency in
white LED applications. The devices can be used
to produce current levels up to 20mA for each
output from a 2.7V to 5.5V input. Low external
parts counts (two 1μF flying capacitors and two
small bypass capacitors at VIN, and OUT) make
the AIC1843 ideal for small, battery-powered
applications.
2.7V to 5.5V Input Voltage Range
Low Shutdown Current: ≦1µA
Regulated 20mA Full-Scale Output Current
32-Position Linear Scale with Digital Control
High Accuracy Brightness Matching
33% Less Input Current Than Doubler Charge
Pump
No Inductors Required
Build-in Soft-Start
Current Limit and Over Temperature Protection
EN/SET interface is used to enable, disable and
set the LED current for a 32 level logic scale LED
brightness control. Built-in current limiting, with
thermal shutdown provides protection to the
AIC1843 against fault conditions. Automatic softstart circuitry prevents excessive inrush current
during start-up. 1MHz high switching frequency is
enable to use tiny external components.
12-Pin DFN Package
APPLICATIONS
Cellular Phones
PDAs
Digital Still Cameras
Handheld Devices
The AIC1843 is available in a 12-pin thin DFN
package.
White LED Backlighting
TYPICAL APPLICATION CIRCUIT
U1
CFLY1
1uF
EN/SET
Vin=2.7V~5.5V
Cin
1uF
Cout
1uF
C1+
C2+
C1-
C2-
EN/SET
D1
VIN
D2
OUT
D3
GND
D4
CFLY2
1uF
AIC1843
Analog Integrations Corporation
3A1, No.1 Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan
TEL: 886-3-5772500
FAX: 886-3-5772510 www.analog.com.tw
DS-1843G-03 080907
1
AIC1843
ORDERING INFORMATION
PIN CONFIGURATION
AIC1843XXXXX
DFN-12 with heat sink
TOP VIEW
PACKING TYPE
TR: TAPE & REEL
BG: BAG
PACKAGE TYPE
DE: DFN-12 with heat sink
(3x3x0.75-0.5mm)
DG: DFN-12 without heat sink
(3x3x0.75-0.5mm)
G: Green Package
C2+
1
12 C2-
OUT
2
11 GND
C1-
3
C1+
4
D4
D3
10 VIN
(GND)
9
EN/SET
5
8
D1
6
7
D2
DFN-12 without heat sink
TOP VIEW
Example: AIC1843GDETR
in Green Package DFN-12 With Heat
Sink Package and Tape & Reel
Packing Type
AIC1843GDGTR
in Green Package DFN-12 Without
Heat Sink Package and Tape & Reel
Packing Type
C2+
1
12 C2-
OUT
2
11 GND
C1-
3
10 VIN
C1+
4
9
EN/SET
D4
5
8
D1
D3
6
7
D2
ABSOLUTE MAXIMUM RATINGS
VIN Voltage ......................................................................................................................................6.0V
OUT pin Voltage...............................................................................................................................6.0V
EN/SET pin Voltage .........................................................................................................................6.0V
Operating Temperature Range ........................................................................................ -40°C to 85°C
Junction Temperature ...................................................................................................................125°C
Storage Temperature Range ......................................................................................... -65°C to 150°C
Lead Temperature (Soldering 10s) ...............................................................................................260°C
Thermal Resistance Junction to Ambient RθJA (Assume no ambient airflow, mounted on PCB)
DFN-12 with heatsink
DFN-12 without heatsink
………………………………………………………………………. 50°C /W
………………………………………………
90°C /W
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
2
AIC1843
ELECTRICAL CHARACTERISTICS
(VIN=3.6V, EN/SET = IN, CIN = C1 = C2 = COUT = 1μF, TA=25°C, Unless otherwise specified.)
(Note1)
PARAMETER
TEST CONDITIONS
Operating Voltage
Undervoltage-Lockout Threshold
MIN.
2.7
VIN falling
2.25
Undervoltage-Lockout Hysteresis
2.45
Active, No Load Current
Shutdown Current
EN = 0
Output Current
1
18
3.0V ≦ VIN ≦ 5.5V
20
-1.5
LED to LED Current Matching
(Note2)
3
Soft-Start Time
UNITS
5.5
V
2.60
V
mV
2
mA
1
μA
22
mA
1.5
%/V
7
%
400
Switching Frequency
0.75
Enable Threshold Low
VIN = 2.7V to 5.5V
Enable Threshold High
VIN = 2.7V to 5.5V
EN/SET Low Time
1
1.25
MHz
0.5
V
V
0.3
75
50
EN/SET Off Timeout
300
VIN = 5.5V
μs
1.4
Minimum EN/SET High Time
EN/SET Input Leakage
MAX.
120
Operating Current
Output Current Line Regulation
TYP.
-1
μs
ns
500
μs
1
μA
Thermal Shutdown Threshold
150
°C
Thermal Shutdown Hysteresis
25
°C
Note 1: Specifications are production tested at TA=25°C. Specifications over the -40°C to 85°C operating
temperature range are assured by design, characterization and correlation with Statistical Quality
Controls (SQC).
Note 2: Current matching define: (ILED1-ILED2) / (ILED1+ILED2), between any two outputs
3
AIC1843
TYPICAL PERFORMANCE CHARACTERISTICS
VEN
VEN
Vo
Vo
VD
VD
IIN
IIN
Vin=3.6V
Vin=3.6V
Fig2: Shutdown Timeout
Fig1: Enable Transient Response
VIN
VIN
Vo
Vo
VD
VD
Fig3: 40mA load at Vin=3.0V
Fig4: 80mA load at Vin=3.0V
VIN
VIN
Vo
Vo
VD
VD
Fig5: 40mA load at Vin=3.6V
Fig6: 80mA load at Vin=3.6V
4
AIC1843
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
V IN
V IN
Vo
Vo
VD
VD
Fig7: 40mA load at Vin=4.2V
Fig8: 80mA load at Vin=4.2V
EN/SET
EN/SET
IDIODE
IDIODE
Fig6: EN/SET Pin 10kHz Clock Transient
Fig7: EN/SET Pin 100kHz Clock Transient
1.50
Quiescent Current (mA)
EN/SET
1.25
IDIODE
1.00
0.75
0.50
3.0
Fig8: EN/SET Pin 1MHz Clock Transient
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Fig12: Quiescent Current vs. Input Voltage
5
AIC1843
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
1.250
Quiescent Current (mA)
Quiescent Current (mA)
1.5
1.4
1.3
T = 25 OC
1.2
O
T = -40 C
1.1
T = 85 OC
1.0
0.9
3.5
3.0
4.0
4.5
5.0
1.225
1.200
1.175
1.150
1.125
1.100
-40
5.5
Normalized LED current
Shutdown Current (µA)
40
60
80
100
1.10
0.4
0.3
0.2
0.1
-20
0
20
40
60
80
1.05
1.00
0.95
0.90
-40
100
0
20
40
60
80
100
o
Temperature ( C)
Fig15: Shutdown Current vs. Temperature
1.20
1.15
1.15
1.10
T = 25 OC
1.05
T = -40 OC
T = 85 OC
0.95
Frequency (MHz)
1.20
1.00
-20
Temperature ( oC)
Fig16: Normalized LED Current vs. Temperature
o
Frequency (MHz)
20
Temperature ( C)
Fig14: Quiescent Current vs. Temperature
0.5
0.90
0
o
Input Voltage (V)
Fig13: Quiescent Current vs. Input Voltage
0.0
-40
-20
1.10
1.05
1.00
0.95
3.0
3.5
4.0
4.5
5.0
Input Voltage (V)
Fig17: Frequency vs. Input Voltage
5.5
0.90
-40
-20
0
20
40
60
80
100
o
Temperature ( C)
Fig18: Frequency vs. Temperature
6
AIC1843
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
80
Vin > 3.2V
Output Current (mA)
70
Vin = 3.0V
60
50
Vin = 2.7V
40
30
20
10
0
0
4
8
12
16
20
24
28
32
Digital Code
Fig19: 32 Levels Current Setting with 4 LEDs
Fig20: Efficiency vs. Supply Current
90
90
3 LEDs (60mA)
85
80
80
Efficiency (%)
Efficiency (%)
2 LEDs (40mA)
85
VF = 3.75V
75
70
65
60
3.0
VF = 3.6V
VF = 3.45V
3.2
3.4
3.6
3.8
4.0
70
65
4.2
VF = 3.75V
75
60
3.0
VF = 3.6V
VF = 3.45V
3.2
3.4
3.6
3.8
4.0
4.2
Supply Voltage (V)
Fig22: Efficiency vs. Supply Voltage
Supply Voltage (V)
Fig21: Efficiency vs. Supply Voltage
90
4 LEDs (80mA)
Efficiency (%)
85
80
VF = 3.75V
75
70
65
60
3.0
VF = 3.6V
VF = 3.45V
3.2
3.4
3.6
3.8
4.0
4.2
Supply Voltage (V)
Fig23: Efficiency vs. Supply Voltage
7
AIC1843
BLOCK DIAGRAM
C1
C2
1uF
1uF
C1P
OSC
C1N
C2P
C2N
VOUT
1.5X CHARGE PUMP
COUT
1uF
VIN
SS
UVLO
OTP
OCP
CIN
OVP
1uF
EN/SET
EN & BIAS
REFERENCE
CURRENT
CONTROLLER
COUNTER
ILED1
ILED2
ILED3
ILED4
D1
D2
D3
D4
LED1
LED2
LED3
LED4
GND
PIN DESCRIPTIONS
D1:
Current source output.
D2:
Current source output.
D3:
Current source output.
D4:
Current source output.
performance, OUT should bypass a 1µF
(min.) low ESR ceramic capacitor with the
shortest distance to ground.
GND: Ground. Connect GND as close as possible
to system ground and to the ground of the
input bypass capacitor.
C1+: Flying capacitor 1 positive terminal.
VIN: Input supply voltage. Bypass a 1uF (min.)
low ESR ceramic capacitor to GND as
close to device as possible. The input
voltage range is 2.7V to 5.5V.
C1-: Flying capacitor 1 negative terminal.
C2+: Flying capacitor 2 positive terminal.
C2-:
Flying capacitor 2 negative terminal.
OUT: Charge
pump
output.
For
the
best
EN/SET: Enable and current set pin.
8
AIC1843
APPLICATION INFORMATION
Efficiency
The efficiency of AIC1843 for ideal 1.5X charge
Operation
pumps intended for WLED backlighting. This kind
pump can be simply defined as:
×I
P
V
V
×I
V
η = OUT = OUT OUT = OUT OUT = OUT
PIN
VIN × IIN
VIN × 1.5I OUT 1.5VIN
of converter uses capacitors to store and transfer
The actual efficiency will decrease as the result
energy. Since the capacitors can’t change to the
from internal switching loss.
The AIC1843 is a high efficiency 1.5X charge
voltage level abruptly, the voltage ratio of VOUT to
VIN is limited. Capacitive voltage conversion is
obtained by switching a capacitor periodically.
Refer to Fig. 20, during the “on” state of internal
clock, Q1, Q4 and Q7 are closed, which charges
CFLY1 and CFLY2 to 1/2VIN level. During the “off”
state, Q2, Q3, Q5 and Q6 are closed. The output
voltage is VIN plus VCFLY, that is, 1.5VIN.
VIN
CIN
Q1
Q2
Q3
CFLY1
Q5
Q4
CFLY2
Q6
The AIC1843 D1 to D4 are constant current
outputs which source up to 20mA respectively to
drive four WLEDs. The LED current is set via
serial interface by the EN/SET pin, which is based
on a digital sacle. The interface records rising
VOUT
edges of the EN/SET pin, and counts them into 32
current level settings where each code is
COUT
Q7
Fig. 20 The circuit of 1.5X charge pump
The AIC1843 only requires one 1µF ceramic
capacitor for CIN, one 1µF ceramic capacitor for
COUT and two 1uF ceramic capacitors for the
charge pump flying capacitors.
WLED Current Level Setting
0.625mA greater than previous code. Code 1 is
the lowest current scale, 0.625mA, and Code 32
is full scale, 20mA. The LED current appears
linear with each increasing code. The first rising
edge enables the device and sets the LED output
current to the lowest setting level, 0.625mA. After
32nd clock, the LED output returns to state 1. The
EN/SET pin has to remain high to keep the LED
output current to programmed level when the final
clock is input.
9
AIC1843
20
Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
18
16
14
ILED(mA)
12
10
8
6
4
2
0
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31
Digital Code
EN/SET Interface
The 2
nd
WLED Current
0.625
1.250
1.875
2.500
3.125
3.750
4.375
5.000
5.625
6.250
6.875
7.500
8.125
8.750
9.375
10.000
Code
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
WLED Current
10.625
11.250
11.875
12.500
13.125
13.750
14.375
15.000
15.625
16.250
16.875
17.500
18.125
18.750
19.375
20.000
st
pulse should be later than 1 pulse for a
The EN/SET timing is as the diagram shown
soft start time at least to maintain a correct LED
below. The first rising edge enables the device
output current level. The counter can be clocked
and sets the LED output current to the lowest
up to 1MHz, so the intermediate scales are not
setting level. The AIC1843 reaches full capaciity
visible.The EN/SET has to hold high to keep the
after typically 400us soft start time. During the soft
output LED current to programmed level when the
start period, multiple clock pulses may be inserted,
final clock is input. When the EN/SET keeps a low
they will be missed cause the counter of EN/SET
for the tSHDN timeout period or longer, the AIC1843
interface will work after soft start time.
is shutdown.
EN
t (LO)
0.3us to 75us
t (SOFT-START)
400us
I(LED)
SHDN
1BIT
2
3
4
5
6
7
t (HI)
>50ns
8
9
10
11
12
.
.
.
.
29
30
31
32
t (SHDN)
300us
1
2
3
4
SHDN
Current Setting Diagram
10
AIC1843
Open-Circuit Protection
for genernal application.
In any cases of open output circuit, the LEDs are
To reduce noise and ripple, low ESR ceramic
disconnected from the circuit or the LEDs are
capacitor is recommended for CIN and COUT. The
failed, etc., the output voltage will limit approxi-
value of COUT determines the amount of output
mately to 5V.
ripple voltage. An output capacitor with larger
value results in smaller ripple. CFLY is critical for
the charge pump which affects turn on time. The
larger CFLY is, the higher output current obtains.
Thermal Protection
When
the
temperature
of
device
exceeds
approximately 150°C, the thermal protection will
shut the switching down and the temperature will
reduce afterwards. Once the temperature drops
However, large CIN and COUT are required when
large CFLY applies. The ratio of CIN (as well as
COUT) to CFLY should be approximately 1:1 to
10:1.
below approximately 125°C, the charge pump
switching circuit will re-start. Even though all four
outputs shorted to ground at maximum 80mA, the
Layout Considerations
die temperature will not increase sufficiently to
Due to the switching frequency and high transient
enable the thermal protection resulting from its
current of AIC1843, careful consideration of PCB
low thermal resistance.
layout is necessary. The CIN should be connected
as close to the IC as possible. The ground of CIN
and COUT should be placed as close as possible.
To achieve the best performance of AIC1843,
Capacitor Selection
Four external capacitors, CIN, COUT, CFLY1, and
CFLY2,
determine
AIC1843
performances.
Optimum performance can be obtained by using
low ESR ceramic capacitors. A 1uF ceramic
minimize
the
distance
between
every
two
components and also minimize every connection
length with a maximum trace width. Make sure
each device connects to immediate ground plane.
capacitor for all four capacitors is recommended
11
AIC1843
Application Example
Ⅰ. When using the AIC1843 to drive fewer than
corresponding LED current still enables.
four LEDs, keep current output float. The
U1
CFLY1
1uF
EN/SET
Vbattery
Cin
1uF
Cout
1uF
C1+
C2+
C1-
C2-
EN/SET
D1
VIN
D2
OUT
D3
GND
D4
CFLY2
1uF
AIC1843
Ⅱ.Any combination of output may be connected
current source. This feature is useful to drive
in parallel to deliver a single power output to
pre-wire LED backlight modules, which is
drive a LED module. The maximum output
connected in parallel structure circuit.
current is the sum of parallel-connected
U1
CFLY1
1uF
EN/SET
Vbattery
Cin
1uF
Cout
1uF
C1+
C2+
C1-
C2-
EN/SET
D1
VIN
D2
OUT
D3
GND
D4
AIC1843
CFLY2
1uF
LED Module
12
AIC1843
PHYSICAL DIMENSIONS (unit: mm)
DFN-12 with heat sink (3x3x0.75-0.5mm)
D2
D
12
E
E2
L
7
6
e
A3
A
PIN#1
b
SEATING PLANE
S
Y
M
B
O
L
A
1
DFN 12L-3x3x0.75-0.5mm
MILLIMETERS
MIN.
MAX.
0.70
0.80
A3
0.20 BSC
b
0.18
0.30
D
2.90
3.10
D2
2.20
2.40
E
2.90
3.10
E2
1.60
1.80
0.50 BSC
e
L
0.35
0.45
Note :
1. DIMENSION AND TOLERANCING CONFORM TO ASME Y14.5M-1994.
2.CONTROLLING DIMENSIONS：MILLIMETER，CONVERTED INCH
DIMENSION ARE NOT NECESSARILY EXACT.
13
AIC1843
DFN-12 without heat sink (3x3x0.75-0.5mm)
D
7
E
L
12
6
BOTTOM VIEW
S
Y
M
B
O
L
A3
A
TOP VIEW
1
e
PIN#1
DFN 12L-3x3x0.75-0.5mm (Without Heat Sink)
A
MILLIMETERS
0.70
A3
b
SEATING PLANE
SIDE VIEW
MAX.
MIN.
0.80
0.203 BSC
b
0.20
0.30
D
2.90
3.10
E
2.90
e
L
3.10
0.500 BSC
0.60
0.70
Note : 1. DIMENSION AND TOLERANCING CONFORM TO ASME Y14.5M-1994.
2.CONTROLLING DIMENSIONS：MILLIMETER，CONVERTED INCH
DIMENSION ARE NOT NECESSARILY EXACT.
Note:
Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry
other than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result
from its use. We reserve the right to change the circuitry and specifications without notice.
Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are
devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when
properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the
user.
14