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FAN5609
LED Driver with Adaptive Charge Pump DC/DC Converter
Features
* * * * * Parallel LED Driver Supports All Forward Voltages Adaptive VOUT Adjustment to the Highest Diode Voltage Internally Matched LED Current Sources No External Components Needed to Set LED Current Built-in Charge Pump has Three Modes of Operation: - Linear Regulation VIN > 4.2V - 3/2 DC-DC Converter and Regulation 3.6VApplications
* * * * * Cell Phones Handheld Computers PDA, DSC, MP3 Players Keyboard Backlight LED Displays
Description
The FAN5609 generates regulated output current from a battery with input voltage varying between 2.7V to 5.5V. Switch reconfiguration and fractional switching techniques are utilized to achieve high efficiency over the entire input voltage range. A proprietary internal circuitry continuously monitors each LED current loop and automatically adjusts the generated output DC voltage to the lowest minimum value required by the LED having the highest forward voltage. This adaptive nature of the FAN5609 eliminates the need for LED pre-selection (matching) and ensures operation at high efficiency. When the input voltage is sufficiently high to sustain the programmed current level in the LEDs, the FAN5609 re-configures itself to operate as a linear regulator, and the DC-DC converter is turned off. An internal two-bit digital to analog converter provides programmability of the output currents. Only two 0.1F bucket capacitors and two 4.7F input/output capacitors are needed for proper operation. Soft-start circuitry prevents excessive current draw during power on. The device has built-in short circuit protection.
* * * * * * * * * * * * * *
Typical Application
VOUT COUT
VIN CIN
VOUT VIN IN A
LED-
LED-
LED-
LEDCAPCAP2 CAP+ CAP+ CAP1
D A C
FAN5609
GND
IN B
CAP-
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FAN5609
PRODUCT SPECIFICATION
Pin Assignments
NC CAP2+
13 12 11 10 9 5 6 7 8
Top-View
VIN VOUT GND B A LEDLEDCAP2CAP2+ CAP1+ CAP1NC LEDLEDCAP214
16
15
FAN5609
VIN VOUT GND B
NC
1 2 3 4
CAP1+ CAP1NC LED-
LED-
LED-
FAN5609 14-Lead TSSOP
FAN5609 4x4mm 16-Lead MLP
Pin Descriptions
FAN5609 Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 14L-TSSOP VIN VOUT GND B A LED LED LED LED NC CAP1CAP1+ CAP2+ CAP24mmX4mm 16L-MLP VIN VOUT GND B A LED LED LED LED NC CAP1CAP1+ CAP2+ CAP2NC NC Input Output to LEDs Anode Ground DAC B DAC A 4th LED Cathode 3rd LED Cathode 2nd LED Cathode 1st LED Cathode No Connection Bucket capacitor negative terminal Bucket capacitor positive connection Bucket capacitor positive terminal Bucket capacitor negative connection No Connection No Connection Pin Function Description
Test Circuit
CAP2 NC NC VIN = 2.7V to 5.5V 1 CIN VOUT COUT 4.7F VL 4 VH 5 8 9 4.7F FAN5609 NC 16 0.1F 13 12
CAP1 0.1F
VH VL
4 White LEDs Fairchild QTLP670C-IW Super Bright LED
All capacitors are Ceramic chip capacitor
2
LED-
A
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PRODUCT SPECIFICATION
FAN5609
Absolute Maximum Ratings
Parameter VIN, VOUT, A, B Voltage to GND CAP+, CAP-, to GND VOUT Short Circuit Duration Lead Soldering Temperature (10 seconds) Operating Junction Temperature Range Storage Temperature Electrostatic Discharge Protection Level (Note 1) HBM CDM -55 4 2 Min -0.3 -0.3 Max 6.0 VIN + 0.3 INDEFINITE 300 150 150 C C C kV Unit V V
Recommended Operating Conditions
Parameter Input Voltage Range, VIN Operating Ambient Temperature Range Min 2.7 -40 25 Typ Max 5.5 85 Unit V C
DC Electrical Characteristics
Unless otherwise noted, VIN =3V to 5.5V, TA = 25C. Refer to "Test Circuit". Boldface values indicate specifications over the ambient operating temperature range.
Parameter Conditions Min. Typ. Max. Units
Quiescent Current Output Current Accuracy INOM = 20mA LED to LED Current Matching Efficiency Input A, B Threshold VIN at Configuration Change Oscillator Frequency Supply Current, "OFF Mode"
VOUT = 5.5V, No Load A = High B = High VIN = 5.5V A = B = High VIN = 4.5V VIN = 3V Low High From 1:1 to 3:2 From 3:2 to 2:1 0.80 0 0.6 x VIN 17 -5
1.5 20
4 23 +5
mA mA % %
85 to75 65 to 55 0.3 x VIN VIN 4.2 3.6 1 1.2 2
V V MHz A
Note: 1. Using Mil Std. 883E, method 3015.7(Human Body Model) and EIA/JESD22C101-A (Charge Device Model)
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FAN5609
PRODUCT SPECIFICATION
Block Diagram
1F
VIN
Linear Regulator
VOUT Voltage Selector
A DAC B D R I V E R S Power Good P U M P
On Off And Current Range
Oscillator
Bandgap Reference Range Selection
Reference Analog Detector
5F
I. LIM.
I. LIM.
Ref2 Ref1 Regulator Ref3
Mode Change VIN Ref4 (BG)
GND
1F
Circuit Description
The FAN5609's switched capacitor DC/DC converter automatically configures its internal switches to achieve high efficiency and to provide tightly regulated output currents for the LEDs. An analog detector determines which diode requires the highest voltage in order to sustain the pre-set current levels, and adjusts the pump regulator accordingly. Every diode has its own linear current regulator. In addition, a voltage regulator controls the output voltage when the battery voltage is within a range where linear regulation can provide maximum possible efficiency. If the battery voltage is too low to sustain the diode current in the linear mode, a fractional 3:2 charge pump is enabled. When the battery voltage drops further and this mode is no longer sufficient to sustain proper operation, the pump is automatically reconfigured to operate in 2:1 mode. As the battery discharges and
the voltage decays, the FAN5609 switches between modes to maintain a constant current through LED throughout the battery life. The transition has hysteresis to prevent toggling.
Supply Voltage
The internal supply voltage for the device is automatically selected from VIN or VOUT pins, whichever is higher. Soft Start The soft-start circuit limits inrush current when the device is initially powered up and enabled. The reference voltage controls the rate of the output voltage ramp-up to its final value. Typical start-up time is 1ms. The rate of the output voltage ramp-up is controlled by an internally generated slow ramp, and an internal variable resistor limits the input current.
4
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I. LIM.
I. LIM.
Low Battery Ref.
PRODUCT SPECIFICATION
FAN5609
Switch Configuration
VIN
VIN VOUT
+ CAP1 VOUT = 2 X VIN
+
CAP2 GND
-
COUT
Figure 1 Step-up, 2:1 configuration. Switch positions shown in charge phase. Reverse all switches for pump phase.
GND Figure 2 Step-up 3:2 configuration Switch positions shown in charge phase. Reverse all switches for pump phase.
Shutdown and Short Circuit Current Limit Set both DAC inputs low to shut down the device. Built-in short circuit protection limits the supply current to a maximum of 50mA. Digital Control A digital-to-analog converter (DAC) allows selection of the following modes: OFF, 7mA, 14mA, 20mA, per diode. By turning the IN B pin ON and OFF, the current can be modulated between 7 to 20mA to achieve any IAverage value (PWM). In PWM mode, the modulating frequency has to be set sufficiently high in order to avoid a flickering effect (100Hz to 1kHz). A B ILED 0 0 OFF 1 0 7mA 0 1 14mA 1 1 20mA
Digital Control with PWM
Any input can be modulated by a pulse train of variable duty cycle (). By turning ON and OFF DAC inputs A or B, the current can be continuously modulated to any average value between 1 to 19mA. For a maximum range of LED current, both A&B can be modulated at the same time.
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5
FAN5609
PRODUCT SPECIFICATION
Digital Control with PWM
A is PWM and B is Low. ILED (Average) = x 7mA, where is Duty Cycle. (Note 2)
A Input (PWM)
30% Duty Cycle
ss
70% Duty Cycle 1KHz 1KHz
B Input (0)
ILED (Average) = 0.7 x 7mA = 4.9mA ILED (Average) = 0.3 x 7mA = 2.1mA ILED 0mA
ss
OFF
A is High and B is PWM. ILED (Average) = 6mA + x 12mA, where is Duty Cycle. (Note 3, 4)
A Input
B Input (PWM)
30% Duty Cycle 1KHz
ss
70% Duty Cycle 1KHz
ILED (Average) = 7mA + 0.7 x 14mA = 16.8mA
ILED (Average) = 7mA + 0.3 x 14mA = 11.2mA
ILED
0mA
ss
OFF
Notes: 2. Proportionally select the duty cycle to achieve a typical LED current between 1mA to 6mA. 3. If either input A or B is continuously high, the other input can be modulated at a maximum rate of 30kHz. Otherwise the maximum rate of modulation should be limited to 1kHz. 4. Proportionally select the duty cycle to achieve a typical LED current between 8mA to 19mA.
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PRODUCT SPECIFICATION
FAN5609
Digital Control with PWM (Continued)
A and B are PWM. ILED (Average) = x 20mA, where is Duty Cycle. (Note 3, 5)
A Input (PWM)
30% Duty Cycle 1KHz
ss
70% Duty Cycle 1KHz
B Input (PWM)
30% Duty Cycle
ss
70% Duty Cycle
ILED (Average) = 0.7 x 20mA = 14mA
ILED (Average) = 0.3 x 20mA = 6mA
ILED
0mA
ss
OFF
Notes: 5. Proportionally select the duty cycle to achieve a typical LED current between 1mA to 19mA.
Application Information
Selecting Capacitors
It is important to select the appropriate capacitor types and the values for use with the FAN5609. These capacitors determine parameters such as power efficiency, maximum sustainable load current by the charge pump, input and output ripple and start-up time. In order to reduce ripple, both CIN and COUT should be low ESR capacitor. Increasing the COUT capacitor reduces the output ripple voltage. However this will increase the power-on time. The CIN value controls input ripple. If necessary, this ripple can be further reduced by powering the FAN5609 through a very small series inductor filter, as shown in Figure 3.
CAP1 and CAP2 control the current capability of the charge pump and affect the overall efficiency of the system. A lower value will improve efficiency, but it may limit the LED's currents at low input voltage. A capacitor of 100nF is optimal for 4 x 20 mA load over the entire input voltage range of 2.7V to 4.2V. To save space and cost, and to increase efficiency, this value may be reduced to 10nF for loads less than 4 x 7mA. Pulse-Width-Modulated (PWM) Mode Conversion errors are minimized and the best LED to LED matching is achieved over the entire range of average current settings, when PWM brightness control is used to modulate the LED current between zero and the maximum value (A=1, B=1).
PC Board Layout
Input Power Supply 100nH 0.1F 4.7F VIN FAN5609 GND For best performance, a solid ground plane is recommended on the back side of the PCB. The ground tails of CIN and COUT should be connected together close to the GND pin of IC.
Figure 3.
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FAN5609
PRODUCT SPECIFICATION
Typical Performance Characteristics
TA = 25C, CIN =COUT = 4.7F, CAP1 = CAP2 = 0.1F, using Fairchild's QTLP670C-IW Super Bright LED.
Regulated LED Current vs LED Forward Voltage
Regulated LED Current (mA)
20.4
DAC Threshold Voltage vs Input Voltage
DAC Inputs Threshold Votlage (V)
2.2 2.0 1.8 1.6 1.4 1.2 1.0 2.5
20.2
20.0
19.8
19.6 3.0 3.2 3.4 3.6 3.8
3.0
3.5
4.0
4.5
5.0
5.5
LED Forward Voltage (V)
LED Forward Voltage (V)
Supply Current vs Input Voltage (4 LEDs)
180 160 25
Regulated LED Current vs Input Voltage
A = 1, B = 1 20
Supply Current (mA)
140 A = 1, B = 1 120 100 80 60 40 20 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 A = 0, B = 1 A = 1, B = 0
LED Current (mA)
15
A = 0, B = 1
10
5
A = 1, B = 0
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Input Voltage (V)
Efficiency vs Input Voltage (4 LEDs x 20mA)
0.9 1.6
Shutdown Current vs Input Voltage
A = 0, B = 0
Shutdown Current (A)
0.8
1.4
Efficiency
0.7
1.2
0.6
1.0
0.5
0.8
0.4 2.5
3.0
3.5
4.0
4.5
5.0
5.5
0.6 2.5
3.0
3.5
4.0
4.5
5.0
5.5
VIN(V)
Input Voltage (V)
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PRODUCT SPECIFICATION
FAN5609
Mechanical Dimensions
14-Lead TSSOP Package
14
8
6.4
4.40.1 -B-
4.16 TYP 7.72 TYP
3.2
1.78 TYP 0.2 C BA 0.65 TYP D
1
PIN #1 IDENT.
7
ALL LEAD TIPS
0.42 TYP
LAND PATTERN RECOMMENDATION
0.1 C ALL LEAD TIPS
0.25 0.09-0.20 0.60.1 SEATING PLANE 0 -8
1.1 MAX TYP -C0.19 - 0.30 TYP 0.65 TYP
0.9 0.10 0.05 TYP
0.19-0.30 M A B S C S
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FAN5609
PRODUCT SPECIFICATION
Mechanical Dimensions
4mmX4mm 16-Lead MLP Package
2.64 4.0 A B 16 13
0.15 C 2X
1
12 3.04 4.50
2.64 4.0 4 9
(0.73) 5 0.15 C 1.00 MAX 0.10 C (0.20) 0.65 TYP 8 0.42 TYP
TOP VIEW
2X
RECOMMENDED LAND PATTERN
0.05 0.00 SEATING PLANE
C
SIDE VIEW
2.80 2.50
5
8
4
9 2.80 2.50 0.65
1
12
PIN #1 IDENT
16 0.65
13 0.25~0.35 0.10 M C A B 0.10 M C
BOTTOM VIEW NOTES: A. B. C. CONFORMS TO JEDEC REGISTRATION MO-220, VARIATION VGGC-3, DATED AUG/2002 DIMENSIONS ARE IN MILLIMETERS. DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994
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FAN5609
PRODUCT SPECIFICATION
Ordering Information
Product Number FAN5609 Package Type 14-Lead TSSOP 4mmx4mm 16-Lead MLP Order Code FAN5609MTCX FAN5609MPX
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) 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 of the user.
www.fairchildsemi.com 5/30/03 0.0m 005 Stock#DS30005609 2003 Fairchild Semiconductor Corporation
2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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