MPS MP1523DT Precision 6-lamp white led driver Datasheet

MP1523
Precision 6-Lamp
White LED Driver
Monolithic Power Systems
INITIAL RELEASE
DESCRIPTION
FEATURES
The MP1523 is a 5-pin SOT23 step-up
converter designed for driving up to six (6)
series white LEDs from a single-cell Lithium
Ion battery. The MP1523 uses a current
limited, variable frequency architecture to
regulate the LED current, which is measured
through an external current sense resistor. Its
low 0.4V feedback threshold reduces power
loss and improves efficiency. To prevent
damage due to an open circuit condition, the
BIAS pin can measure the output voltage and
turn off the converter if an over-voltage
condition is present.
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The MP1523 includes under-voltage lockout,
current limiting, and thermal overload
protection to prevent damage in the event of
an output overload. The MP1523 is available in
a small 5-pin SOT23 package.
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On Board Power MOSFET
Drives up to 6 White LEDs
Up to 90% Efficiency
Over 80mA Output Current Capacity
Open Load Shutdown
Low 0.4V Feedback Threshold
UVLO, Thermal Shutdown
Soft-Start
Internal Current Limiter
Available in SOT23-5 Package
Evaluation Board Available
APPLICATIONS
Cell Phones
Handheld Computers and PDAs
Digital Still and Video Cameras
Small LCD Displays
, “MPS”, “Monolithic Power Systems”, and “The Future of Analog IC
Technology” are Registered Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
A
VIN
2.7V to 5.5V
B
100
EN
4
2
5
1
BIAS
SW
EN
MP1523
GND
FB
3
EFFICIENCY (%)
90
Up To
6 LEDs
80
70
VIN = 5V
VIN = 4V
VIN = 3V
60
50
MP1523-TAC-S01
5
10
15
20
LED CURRENT (mA)
25
MP1523-EC01
07/04, Rev. 1.6
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1
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
ABSOLUTE MAXIMUM RATINGS (1)
PACKAGE REFERENCE
BIAS ............................................... -0.3V to 28V
SW .................................................. -0.5V to 28V
All Other Pins.................................... -0.3V to 6V
Storage Temperature ...............-55°C to +150°C
TOP VIEW
1
GND
2
FB
3
5
BIAS
A3XX
SW
Recommended Operating Conditions
4
BIAS Supply Voltage ....................... 2.7V to 25V
Output Voltage....................................VIN to 25V
Operating Temperature ..............-40°C to +85°C
EN
MP1523_PD01-SOT23-5
Part Number*
Package
MP1523DT
SOT23-5
EV0035
*
(2)
Thermal Resistance
(3)
ΘJA (SOT23-5) ..................................... 220°C/W
ΘJC (SOT23-5) ..................................... 110°C/W
Temperature
-40°C to +85°C
Evaluation Board
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
For Tape & Reel, add suffix –Z (eg. MP1523DT–Z)
For Lead Free, add suffix –LF (eg. MP1523DT–LF–Z)
ELECTRICAL CHARACTERISTICS (4)
VBIAS = VEN = 5.0V, TA = 25°C, unless otherwise noted.
Parameter
Supply Current (shutdown)
Supply Current (quiescent)
Minimum Off Time, Normal
Operation
Minimum Off Time, Start-Up
Undervoltage Lockout
BIAS Under Voltage Lockout
Open Lamp Shutdown Threshold
Enable
EN Threshold
EN Hysteresis
EN Input Bias Current
Feedback Comparator
FB Regulation Threshold
FB Hysteresis (5)
FB Input Bias Current
Output Switch
SW On-Resistance (5)
SW Current Limit
SW Voltage
Thermal Shutdown (5)
Thermal Shutdown Hysterisis (5)
Symbol
Min
IBIAS (OFF)
IBIAS (ON)
Condition
VEN = 0V
VFB = 0.45V
Typ
1
650
Max
3
750
Units
µA
µA
TOFF
VFB = 0V
300
550
700
ns
1.25
1.6
(4)
TOFF
VFB = 0V
UVLO
VBIAS Rising, 100mV Hysteresis
VBIAS Rising
2.1
2.3
28
2.65
V
V
VEN Rising
0.8
1.1
60
1.5
V
mV
µA
VEN = 0V, 5V
1
VFB Falling
380
VFB = 0.2V
-150
ISW = 10µA
300
25
RON
BV
µs
400
10
-80
420
mV
mV
nA
0.5
450
0.6
650
Ω
mA
V
°C
°C
160
15
Notes:
4) First 64 pulses after EN switches high.
5) Guaranteed by design.
07/04, Rev. 1.6
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2
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs VIN
of Figure 2
Line Regulation
of Figure 2 and Figure 3
23
LED CURRENT (mA)
EFFICIENCY (%)
85
80
75
70
2.5
3.0
3.5
VIN (V)
4.0
4.5
MP1523_TPC01
21
19
17
15
2.5
3.0
3.5
VIN (V)
4.0
4.5
MP1523_TPC02
PIN FUNCTIONS
Pin #
Name
1
SW
2
GND
3
FB
Feedback Input. The MP1523 regulates the voltage across the current sense
resistor between FB and GND. Connect a current sense resistor from the bottom of
the LED string to GND. Connect the bottom of the LED string to FB. The regulation
threshold is 0.4V.
4
EN
Regulator On/Off Control Input. A high input at EN turns on the converter, and a low
input turns it off. When not used, connect EN to the input source for automatic
startup. If EN is driven over 6V, place a resistor in series with EN to limit current to
10µA or less. Do not leave EN floating!
5
BIAS
Internal Power Input. BIAS powers the internal circuitry and measures the output
voltage for open circuit protection. Connect BIAS to the output at the top of the LED
string to enable open load shutdown feature (see Figure 3). Connect BIAS to the
input to eliminate open load shutdown feature (see Figure 2).
07/04, Rev. 1.6
Description
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the
power inductor and output rectifier to SW. SW can swing between GND and 25V.
Ground
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3
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
OPERATION
the MP1523 waits until the voltage drops below
the threshold before turning on the MOSFET
again. This process allows for optimal use of
the inductor, while minimizing the output ripple
and size of the output capacitor and maintaining
low operating current.
The MP1523 is a step-up converter that
operates from an input voltage as low as 2.7V
and generates an output voltage up to 25V. The
0.5Ω internal N-Channel power MOSFET is
driven with a variable frequency, constant-peakcurrent architecture for low operating current.
The 550ns minimum off time is extended to
1.6µs during start-up to yield a smooth glitch
free turn-on.
Open Load Shutdown
Open load shutdown is implemented by
connecting the BIAS pin to the output. In the
fault condition where the connection to the LED
string is open, the output voltage will rise up, as
the FB pin has no voltage. Once the output
voltage exceeds 28V, the MP1523 will cease
operation until the EN pin is cycled off and on.
Connecting the BIAS pin to VIN disables open
load shutdown but reduces the chip power
consumption due to the quiescent current.
Variable Frequency Constant-Peak-Current
Operation
When the power MOSFET is turned on the
inductor current increases until the 0.45A
current limit is reached. The internal power
MOSFET is then turned off for a minimum of
550ns. At the end of this 550ns transition if the
FB pin is still lower than the 400mV threshold
the MOSFET will again be turned on, otherwise
BIAS (5)
17V
160K
+
1.23V
20K
EN
(4)
-
Open Load
Shutdown
Comparator
SW
(1)
REGULATOR
INTERNAL
POWER
CONTROL
LOGIC
CURRENT
_
7V
+
450mA
ERROR AMP.
FB
(3)
_
+
400mV
+
-
GND (2)
Figure 1—Functional Block Diagram
07/04, Rev. 1.6
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4
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
APPLICATIONS INFORMATION
Setting the LED current
The LED current is set by the sense resistor
(R2) at FB. The LED current can be calculated
as:
ILED
V
= FB
R2
Where VFB is 400mV. The LED current is set to
20mA if R2 = 20Ω.
Capacitor Selection
A 1µF to 10µF ceramic input capacitor (C1) and
a 0.47µF to 1µF ceramic output capacitor (C2)
are recommended for most applications. A
capacitor (typically 1nF) in parallel with the LED
string improves stability, input and output ripple
especially when large inductance values (10µH
or above) are used. For best stability over a
wide temperature range, use capacitors with an
X5R or X7R dielectric.
Inductor selection
The MP1523 has a 450mA inductor current limit
and can drive up to 6 LEDs at 20mA.
Inductance values (L1) from 4.7µH to 47µH
work satisfactorily. Larger values provide the
best efficiency while small inductor values allow
the smallest inductor size. To prevent
07/04, Rev. 1.6
saturation, use an inductor with a saturation
current rating that matches the device current
limit.
Diode selection
The MP1523’s high switching frequency
demands a high-speed rectifier (D1) for
optimum efficiency. A schottky diode is
recommended due to its fast recovery time and
low forward voltage drop. Ensure the diode’s
average and peak current ratings exceed the
average output current and peak inductor
current. In addition, the diode’s reverse
breakdown voltage must exceed the output
voltage.
Layout
Careful PC board layout is required due to fastswitching. All components must be placed as
close to the IC as possible. Keep the path
between inductor L1, diode D1, and output
capacitor C2 extremely short for minimal noise
and ringing. The feedback components such as
sense resistor R2 must be kept close to the FB
pin to prevent noise injection on the FB pin
trace. The ground return of C1 and C2 should
be tied close to the GND pin. See the MP1523
demo board layout for reference.
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5
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
TYPICAL APPLICATIONS / TEST CIRCUITS
L1
15µH
CDM4D11
D1, B130
VIN = 2.7 to 25V
C1
1µF
4
2
Up to
6 LEDs
1
5
BIAS
EN
C2
4.7µF
Point A
SW
MP1523
EN
FB
GND
3
R2
20Ω
Note: Pin 5 connects to Point A to eliminate Open Load Shutdown Option
Figure 2—One String of up to Six (6) LEDs “without” Open Load Shutdown Option
L1
15µH
CDM4D11
Point B
D1, B130
V IN = 2.7 to 25V
C1
1µF
C2
4.7µF
BIAS
EN
4
2
EN
GND
Up to
6 LEDs
1
5
SW
MP1523
FB
3
R2
20Ω
Note: Pin 5 connects to Point B to enable Open Load Shutdown Option
Figure 3—One String of up to Six (6) LEDs “with” Open Load Shutdown Option
07/04, Rev. 1.6
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6
MP1523 – PRECISION 6-LAMP WHITE LED DRIVER
INITIAL RELEASE
PACKAGE INFORMATION
SOT23-5
2.90±0.100
0
10 TYP.
(2 plcs)
0.950
TYP.
CL
2.80±0.200
1.60±0.100
5
0.950
TYP.
5
0°~3°
0.20 BSC.
Gauge Plane
0.350(MIN)
0.500(MAX)
(5 PLCS)
0.45 ±0.10
C
L
0.127 TYP
0
10 TYP.
(2 plcs)
0
1.15±0.150
10 TYP.
(2 plcs)
SEATING PLANE
0
10 TYP.
(2 plcs)
0.05(MIN)
0.15(MAX)
NOTICE: MPS believes the information in this document to be accurate and reliable. However, it is subject to change without
notice. Contact MPS for current specifications. MPS encourages users of its products to ensure that third party Intellectual
Property rights are not infringed upon when integrating MPS products into any application. MPS cannot assume any legal
responsibility for any said applications.
MP1523 Rev. 1.6
7/14/04
© 2004 MPS, Inc.
Monolithic Power Systems, Inc.
983 University Avenue, Building A, Los Gatos, CA 95032 USA
Tel: 408-357-6600 ♦ Fax: 408-357-6601 ♦ www.MonolithicPower.com
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