RYC9901 Raychem Multi-LED Boost

RYC9901 Raychem Multi-LED Boost
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
GENERAL DESCRIPTION
The RYC9901 device is a low-cost integrated boost
converter IC specifically designed for driving multiLED arrays. It can be operated from a single
Lithium cell or two alkaline cells, and drives up to 7
LEDs. All LEDs are in series, and the RYC9901
device regulates at constant current, yielding
uniform illumination. The RYC9901 device features
an active low enable/ dimming pin and thermal
protection, and is available in a space-saving SOT23-6 package.
FEATURES
•
•
•
•
•
•
Constant current regulation
Up to 700mW output power
1.9V to 5.5V input voltage range
25V maximum output voltage
1µA maximum shutdown current
SOT-23-6 package
APPLICATIONS
•
•
•
•
•
•
Backlight for LCD panels
Cellular telephones
Handy Terminals
PDAs
Portable lighting
Battery-powered backlight applications
TYPICAL APPLICATION SCHEMATIC
6
1
2 RYC9901 5
4
3
ENABLE / DIM
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
1 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
ORDERING INFORMATION
Part Description
RYC9901
Part Number
E67308-000
Package
SOT-23(6L)
Tape and Reel Quantity
2,500 pcs
MATERIALS INFORMATION
ROHS Compliant
ELV Compliant
PIN CONFIGURATION
Pb-Free
DEVICE MARKING
Raychem Logo
FB
GND
PGND
1
6
2
5
3
4
VCC
LX
ENABLE/DIM
9901
Part ID
Top:
Part Number
Bottom: Date code
Lot ID
PIN DESCRIPTION
Pin Number
Pin Name
Pin Function
1
FB
Feedback: This pin is the feedback to the PWM to control the output current. Attach
to a current sense resistor.
2
GND
Ground.
3
PGND
Power Ground.
ENABLE / DIM
Enable: A logic low turns on the converter. A logic high or open turns off the converter.
A PWM signal on this pin dims the output.
5
LX
Switch Node: Connection to internal power MOSFET. Attach to inductor and diode.
6
VCC
VCC. Power input to run the IC.
4
VCC
BLOCK DIAGRAM
L
Clamp
Erro
Am
FB
Current
Comparator
Oscillator
PWM Logic
Reference
Divider
Reference
& Thermal
Protection
ENABLE
PGND
GND
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
2 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2)
Parameter
Min
Max
Units
VCC to GND
-0.3
+6.5
V
Lx to GND
-0.3
33
V
All Other Pins to GND
Continuous Power Dissipation (70°C)
(Derate 5.9mW/°C above 70°C)
Ambient operating temperature
-0.3
VCC + 0.3
V
380
mW
+85
°C
− 65 to +150
°C
-40
Storage temperature
Max lead temperature during soldering (5 sec.)
260
°C
Note 1. Operation beyond absolute maximum rating or improper use may result in permanent damage to the device. Exposure to absolute
maximum rating conditions for extended periods or to conditions beyond absolute maximum rating conditions may adversely affect device
reliability. Functional operation under absolute maximum rating conditions is not implied.
Note 2. Devices are ESD sensitive. Handling precautions recommended. This device is rated at HBM ±2.0 kV.
ELECTRICAL CHARACTERISTICS
(Vcc = +3.5V, TA = 25°C, using circuit in Figure 1, unless otherwise noted)
(The • denotes specifications which apply over the full operating temperature range.)
Parameters
Condition
VCC
Supply voltage
Supply Current
VENABLE = 0V
Disable Supply Current
VENABLE = 3.5V
ENABLE
Threshold
Low-to-High
High-to-Low
Input Current
VENABLE = 0V
VENABLE = 3.5V
Turn-on Time
LX
LX Voltage
Switch Resistance
Current Limit
Current Limit Temperature Variation
FB
Feedback Voltage
Feedback Voltage Temperature
Variation
Other
Switching frequency
Frequency Temperature Variation
•
•
•
•
Min
Typ
Max
Units
1.9
----150
0.15
5.5
260
0.55
V
µA
µA
1.3
1.3
0.05
-0.05
200
1.8
V
V
µA
0.8
-1
1
µs
25
860
600
•
1900
±10
300
•
340
370
mV
%
110
kHz
%
±5
60
•
Maximum Duty Cycle
Thermal Shutdown
Thermal Shutdown Hysteresis
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
85
±10
75
135
10
V
mΩ
mA
%
%
°C
°C
3 of 12
Raychem
Power Management ICs
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RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
TYPICAL CHARACTERISTICS
Switching Waveforms, Pout = 1W
Efficiency, 1W Super-Bright White LED
90.00
85.00
Efficiency (%)
LX
10V/Div
IL
1A/Div
80.00
75.00
70.00
2.5
5 sec/Div
3.5
4
4.5
VCC (V)
LED Current vs. Modulation
Output Current vs. Temperature
25
20
19
20
18
15
LED Current (mA)
10
FPWM = 1KHz
5
VCC = 3.0V
17
16
15
14
13
12
11
Duty Cycle (%)
4.
5
4.
3
4.
1
3.
9
3.
7
3.
5
3.
3
3.
1
2.
9
10
2.
7
100%
90%
85%
80%
75%
70%
65%
60%
55%
50%
45%
40%
35%
30%
25%
20%
0
2.
5
LED Current (mA)
3
Temperature (°C)
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
4 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
TYPICAL CHARACTERISTICS (CONT)
Frequency Normalized at 25°C
Feedback Voltage Normalized at 25°C
1.2
1.1
1.15
1.05
1.1
1
1.05
1
0.95
0.95
0.9
0.9
0.85
0.85
0.8
0.8
-55
-35
-15
5
25
45
65
85
105
125
-55
-35
-15
5
Junction Temperature (ºC)
25
45
65
85
105
125
Junction Temperature (ºC)
Supply Current Normalized at 25°C
Disable Supply Current Normalized at 25°C
10
1.4
9
1.3
8
1.2
7
1.1
6
5
1
4
0.9
3
0.8
2
0.7
1
0.6
-55
0
-35
-15
5
25
45
65
85
Junction Temperature (ºC)
105
125
-55
-35
-15
5
25
45
65
85
105
125
Junction Temperature (ºC)
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
5 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
TYPICAL CHARACTERISTICS (CONT)
LED Current vs. Modulation
LED Current (mA)
25
20
15
10
FPWM = 1KHz
5
90%
100%
85%
80%
75%
70%
65%
60%
55%
50%
45%
40%
35%
30%
25%
20%
0
Duty Cycle (%)
APPLICATION CIRCUIT
C2
L1
D1
D2
C1
D3
R1
1
2
3
6
RYC9901 5
4
ENABLE
U1
Figure X Application Circuit for Two LEDs
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
6 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
TABLE 1. APPLICATION BILL OF MATERIALS FOR FIGURE X
Reference
C1
C2
D1
D2-3
R1
L1
U1
Manufacturer
Example Part #
Any
Any
Zetex
ZHCS400
Fairchild
MV8W00
Any
Coiltronics
SD12-220
Raychem
RYC9901
Quantity
Description
1
1
2.2µF, Ceramic Cap
1µF, Ceramic Cap
1
400mA, 40V Schottky
2
Super-Bright White LEDs
1
13.3Ω
1
22µH, 635mΩ
1
Multi-LED Boost IC
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
Notes
ISAT > 0.575A
7 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
APPLICATION INFORMATION
The RYC9901 device is a low-cost integrated boost
converter IC specifically designed for driving multi-LED
arrays. It can be operated from a single Lithium cell or
two alkaline cells, and drives up to 7 LEDs. All LEDs
are in series, and the RYC9901 device regulates at
constant current, yielding uniform illumination. The
RYC9901 device features an active low enable pin
and thermal protection, and is available in a spacesaving SOT-23-6 package
with L the inductance, Vin the input voltage, T the
period (=12.5µsec), and P the input power (=output
power / efficiency).
As an example, using the circuit in Figure 1, suppose
that L = 10µH, Vin = 3V, and input power = 7.6V *
20mA / 85% = 179mW, with an assumed efficiency of
85%. We calculate that Irms = 132mA. The input
capacitor should be rated to take this ripple current in
steady-state.
Startup
The RYC9901 device does not require a soft-start. It
has a current limit on the LX pin that is designed to
avoid damage to the IC even by a short circuit. At
startup, then, it simply runs at maximum current until
the output capacitor is charged, at which time it enters
normal operation.
Normal Operation
In normal operation, the RYC9901 device is intended
to be operated as a discontinuous conduction mode
non-isolated flyback converter. It boosts the input
voltage to another DC voltage, which then passes
through the series string of LEDs and a sense resistor.
The current is regulated by measuring the voltage
across the sense resistor, and regulating the DC
output voltage to be such that the voltage across the
sense resistor is 340mV.
Input Capacitor
It may be desirable to include an input capacitor to this
circuit. Even though the input to the converter is a
battery, batteries have limited ability to source highfrequency currents. Thus, there may be significant
voltage drops at the input unless an input capacitor is
used.
The input capacitor must be rated to take the AC ripple
current, which is given by:
I rms =
⎛ 2 3P ⎞ 3 2P ⎤
2P ⎡
⎢ LTP ⎜⎜ + 2 ⎟⎟ −
⎥
3Vin ⎢
Vin ⎥
⎝ L Vin T ⎠
⎣
⎦
Output Capacitor
Typical usage will require only a 1µF ceramic
capacitor at the output of the converter. lf a different
capacitor is necessary, the following information may
be used. The output capacitor of a discontinuous
conduction mode flyback converter sees high ripple
current. The capacitor must be rated to take this
current, which is given by:
I rms =
2
P2
3 T (Vin − Vout )3
[
2T (Vin − Vout ) + PTL
]
with L the inductance, Vin the input voltage, Vout the
output voltage, T the period (=10µsec), and P the input
power (=output power / efficiency).
As an example, using the circuit in Figure 1, suppose
that L = 10µH, Vin = 3V, Vout = 7.6V, and input power
= 7.6V * 20mA / 85% = 179mW, with an assumed
efficiency of 85%. We calculate that Irms = 31mA. The
output capacitor must be rated to take this ripple
current in steady-state.
Bootstrap Application
Efficiency of the RYC9901 device is somewhat limited
by the low voltage available on the VCC pin to drive
the internal MOSFET. If a higher voltage is not
available, an alternative is to bootstrap the input. As
shown in Figure 2, this can be accomplished by orring
together the external supply voltage with the voltage
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
8 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
across one of the LEDs, which latter is approximately
3.6V.
Vin
VCC
Figure 2. Bootstrapping Circuit
Enable
The RYC9901 device can be turned off by pulling the
ENABLE pin high. In this condition, there is extremely
low leakage current into the IC, and very low current
into the LEDs, since the supply voltage (minus a diode
drop) is much less than the forward voltage required to
turn on the LEDs.
Disconnecting the LEDs in Shutdown
If it is still desired to disconnect the LEDs when the
RYC9901device is disabled, the circuit in Figure 3 may
be used. When the IC is enabled, the voltage on the
emitter of the PNP will be greater than the input
voltage, and so the transistor will conduct current to
the LEDs. When the IC is disabled, the voltage on the
emitter will be a diode drop less than that on the base,
and so the LEDs will be disconnected.
VIN
Since the switching starts up approximately 200µsec
after ENABLE is asserted, a low frequency PWM
signal applied to the ENABLE pin turns the converter
on and off, dimming the output. Since the switching is
enabled by ENABLE low, the average output current
to the LEDs will be proportional to 1 – DC, with DC the
duty cycle of the PWM signal. As an example,
applying a 1KHz PWM signal with high present for
700µsec, results in a light level that is (1msec –
700µsec) / 1msec = 30% of the level set by the sense
resistor. It is not possible to use this method to
achieve light levels higher than that set by the sense
resistor. If higher light levels are desired, select a
smaller sense resistor. PWM frequencies in excess of
a couple of KHz are not feasible with this method.
The second method for dimming the RYC9901 device
is to add in an analog signal to the FB pin, causing the
IC to generate less current to add up to the total
340mV required on the FB pin. In the example shown
in Figure 4, a high frequency PWM signal is integrated
by an RC filter, which is then added together with the
current sense signal. The resistor value is chosen with
such a value that the HIGH voltage of the PWM is
divided down to approximately 340mV by the resistor
divider formed with the current sense resistor. The
capacitor is chosen to filter the PWM frequency.
2KΩ
FB
10nF
LED
Current
17Ω
20KΩ
3.3V
38KHz
Figure 4. Dimming Circuit
Figure 3. LED Disconnect Circuit
Operation with a High or Low Input Voltage
Dimming
Even with a fixed sense resistor, the RYC9901 device
output current can be dimmed. There are two methods
for dimming, either applying a PWM signal directly to
the ENABLE pin, or else adding an analog signal to
the FB pin.
If the power source available is outside the
recommended operating range of the IC, the
RYC9901 device can still be used to drive LEDs. To
do this, the power source may be connected to the
inductor, while the VCC pin needs to receive a small
amount of current within its operating range.
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
9 of 12
Raychem
Power Management ICs
www.tycopowercomponents.com
RYC9901
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Multi-LED Boost
In the case of a high voltage power source, the
inductor may be attached directly to a voltage up to
about 25V, subject to the limitations mentioned above
about the nature of non-isolated flybacks. The small
current needed for the VCC pin can then be generated
by a low-power resistor and a zener from the high
voltage source. A 5V supply is recommended.
In the case of a voltage power source below the UVLO
of the IC, the inductor may still be operated from the
power source. All that is required is that the small
current required by the RYC9901 be made available
from a higher voltage supply; a 5V supply is
recommended.
Open String
If the output of the RYC9901 device is open, as might
happen if the LED string fails open, the energy stored
in the inductor each cycle is dissipated in the power
device of the IC. Although not recommended, the
RYC9901 device is rated to take this avalanche
energy, which will not damage it, for up to one minute.
If the energy is sufficiently high, the RYC9901 device
may go into thermal shutdown. After cooling off, it will
begin operation again. This cycling should not damage
the IC. The output voltage in open string may rise as
high as 40V, and the output capacitor and diode
should be rated to withstand this voltage in this mode.
Alternatively a 30V zener may be placed in parallel
with the output cap.
Thermal Shutdown
If the RYC9901 device die becomes excessively hot,
the IC should shut itself down. It will then resume
normal operation after cooling down sufficiently.
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
10 of 12
Raychem
Power Management ICs
RYC9901
Multi-LED Boost
www.tycopowercomponents.com
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
PACKAGE INFORMATION
6 Pin SOT-23 PACKAGE NOTES:
1.
2.
3.
4.
5.
Dimensions and tolerance per ANSI Y14.5M-1982.
Dimensions A and B are datums and T is a datum surface.
Controlling dimensions: Millimeters
Dimension A and B do not include mold flash. Mold flash shall not exceed 0.15mm [0.006] per side.
Dimension D does not include interlead flash. Interlead flash shall not exceed 0.25 mm [0.010].
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
11 of 12
Raychem
Power Management ICs
RYC9901
Multi-LED Boost
www.tycopowercomponents.com
Document: SCD 25493
Status: Released
Rev.: D
Rev Date: March 8, 2005
Information furnished is believed to be accurate and reliable. However, users should independently evaluate the suitability of each product for
their applications. Tyco Electronics Corporation assumes no responsibility for the use of its product or for any infringement of patents or other
rights of third parties resulting from the use of its product. No license is granted by implication or otherwise under any patent or proprietary right
of Tyco Electronics except the right to use such product for the purpose for which it is sold. Tyco Electronics reserves the right to change or
update, without notice, any information contained in this publication; to change, without notice, the design, construction, processing, or
specification of any product; and to discontinue or limit production or distribution of any product. This publication supersedes and replaces all
information previously supplied. Without express written consent by an officer of Tyco Electronics, Tyco Electronics does not authorize the use of
any its products as components in nuclear facility applications, aerospace, or in critical life support devices or systems. Tyco Electronics’ only
obligations are those in the Tyco Electronics Standard Terms and Conditions of Sale and in no case will Tyco Electronics be liable for any
incidental, indirect, or consequential damages arising from the sale, resale, use, or misuse of its products.
Raychem is a trademark of Tyco Electronics Corporation.
Tyco Electronics Corporation 308 Constitution Drive, Menlo Park, CA 94025 Tel: (800) 227-4856 Fax: (800) 227-4866
© 2005 Tyco Electronics Corporation.
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