MICREL MIC2293

MIC2292/93
Micrel, Inc.
MIC2292/93
High Frequency PWM White LED Drivers with
Internal Schottky Diode and OVP
General Description
Features
The MIC2292 and MIC2293 are high frequency, Pulse Width
Modulator (PWM) boost regulators optimized for constantcurrent, white LED driver applications. Because of their
constant PWM switching frequencies of 1.6MHz and 2MHz,
respectively, the MIC2292/93 can use the smallest external
components, allowing designers to avoid sensitive IF bands
in their RF applications.
The products feature an internal Schottky diode and two
levels of output overvoltage protection allowing a small size
and efficient DC/DC solution that requires only four external
components.
The 2.5V to 10V input voltage range of MIC2292/3
allows direct operation from 1- and 2-cell Li Ion as well as
3- to 4-cell NiCad/NiMH/Alkaline batteries. The MIC2292/3
products are available in a small size 2mm × 2mm 8-lead
MLF™ package and have a junction temperature range of
–40°C to +125°C.
All support documentation can be found on Micrel’s web site
at www.micrel.com.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2.5V to 10V input voltage
Output voltage up to 34V
Internal Schottky diode
1.6MHz PWM operation (MIC2292)
2.0MHz PWM operation (MIC2293)
Stable with ceramic capacitors
15V and 34V output overvoltage protection options
500mA switch current rating
95mV feedback voltage
<1% line and load regulation
<1µA shutdown current
Over-temperature protection
UVLO
8-lead (2mm × 2mm) MLF™package
–40°C to +125°C junction temperature range
Applications
• White LED driver for backlighting
– Cell phones
– PDAs
– GPS systems
– Digital cameras
– MP3 players
– IP phones
• Constant current power supplies
Typical Application
15µH
10µH
MIC2292-15BML
Li Ion
1µF
VIN
MIC2293-15BML
SW
0.22µF
16V
OUT
FB
EN
GND
Li Ion
1µF
VIN
SW
FB
EN
95mV
GND
6.3Ω
1.6MHz PWM White LED Driver with 15V OVP
0.22µF
16V
OUT
95mV
6.3Ω
2MHz PWM White LED Driver with 15V OVP
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2005
1
M9999-070105
MIC2292/93
Micrel, Inc.
Ordering Information
Part Number
Marking
Code
Overvoltage
Protection
Frequency
Junction
Temp. Range
MIC2292-15BML
Package
SWA
15V
1.6MHz
–40°C to +125°C
8-lead MLF™
MIC2292-15YML
SWA
15V
1.6MHz
–40°C to +125°C
8-lead MLF™
Pb-Free
MIC2292-34BML
SWC
34V
1.6MHz
–40°C to +125°C
8-lead MLF™
Standard
MIC2292-34YML
SWC
34V
1.6MHz
–40°C to +125°C
8-lead MLF™
Pb-Free
MIC2293-15BML
SZA
15V
2MHz
–40°C to +125°C
8-lead MLF™
Standard
Lead Finish
Standard
MIC2293-15YML
SZA
15V
2MHz
–40°C to +125°C
8-lead MLF™
Pb-Free
MIC2293-34BML
SZC
34V
2MHz
–40°C to +125°C
8-lead MLF™
Standard
MIC2293-34YML
SZC
34V
2MHz
–40°C to +125°C
8-lead MLF™
Pb-Free
Pin Configuration
OUT
1
8
PGND
VIN
2
7
SW
EN
3
6
FB
AGND
4
5
NC
EP
8-lead MLF™ (BML)
(Top View)
Fused Lead Frame
Pin Description
Pin Number
Pin Name
1
OUT
Pin Function
Output pin and overvoltage protection (Output): Connect to the output capacitor and LEDs.
2
VIN
Supply (Input): Input voltage.
3
EN
Enable (Input): Logic high enables regulator. Logic low shuts down regulator.
5
NC
No connect (no internal connection to die).
6
FB
Feedback (Input): Output voltage sense node. Connect the cathode of the
LED to this pin. A resistor from this pin to ground sets the LED current.
7
SW
Switch node (Input): Internal power transistor collector.
4,8
GND
Ground (Return): Ground.
EP
GND
Ground (Return): Exposed backside pad.
M9999-070105
2
July, 2005
MIC2292/93
Micrel, Inc.
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) ..................................................... 12V
Switch Voltage (VSW) ......................................–0.3V to 34V
Enable Pin Voltage (VEN) ................................... –0.3 to VIN
FB Voltage (VFB) ............................................................. 6V
Switch Current (ISW) ........................................................ 2A
Ambient Storage Temperature (TS) .......... –65°C to +150°C
Schottky Reverse Voltage (VDA) ................................... 34V
ESD Rating(3) ............................................................... 2kV
Supply Voltage (VIN) ..........................................2.5V to 10V
Output Voltage (VOUT) .......................................VIN to VOVP
Junction Temperature Range (TJ) ............ –40°C to +125°C
Package Thermal Impedance
8-lead MLF™ (θJA) .............................................. 93°C/W
Electrical Characteristics(4)
TA = 25ºC, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 20mA, unless otherwise noted. Bold values indicate –40ºC ≤ TJ ≤ +125ºC.
Symbol
Parameter
VIN
Supply Voltage Range
2.5
VULVO
Under Voltage Lockout
1.8
IVIN
Quiescent Current
ISD
Shutdown Current
VEN = 0V(5)
VFB
Feedback Voltage
(±5%)
IFB
Feedback Input Current
VFB = 95mV
Line Regulation(6)
Load
Regulation(6)
Condition
Min
VFB > 200mV, (not switching)
90
Typ
Max
Units
10
V
2.1
2.4
V
2.5
5
mA
0.1
1
µA
95
100
mV
-450
nA
3V ≤ VIN ≤ 5V
0.5
1
%
5mA ≤ IOUT ≤ 20mA
0.5
2
%
85
DMAX
Maximum Duty Cycle
ISW
Switch Current Limit
VSW
Switch Saturation Voltage
ISW = 0.5A
ISW
Switch Leakage Current
VEN = 0V, VSW = 10V
VEN
Enable Threshold
TURN ON
TURN OFF
IEN
Enable Pin Current
VEN = 10V
fSW
Oscillator Frequency
MIC2292
MIC2293
VD
Schottky Forward Drop
ID = 150mA
IRD
Schottky Leakage Current
VR = 30V
VOVP
Overvoltage Protection
MIC2292/93-15
MIC2292/93-34
TJ
Overtemperature
Threshold Shutdown
90
%
750
mA
450
mV
0.01
1.5
1.4
1.75
13
30
µA
0.4
V
V
20
40
µA
1.6
2.0
1.8
2.25
MHz
MHz
0.8
1
V
4
µA
16
34
V
V
14
32
150
10
Hysteresis
5
°C
°C
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating
the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max),
the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive
die temperature, and the regulator will go into thermal shutdown.
2. This device is not guaranteed to operate beyond its specified operating ratings.
3. Devices are inherently ESD sensitive. Handling precautions required. Human body model.
4. Specification for packaged product only.
5. ISD = IVIN.
6. Guaranteed by design.
July 2005
3
M9999-070105
MIC2292/93
Micrel, Inc.
Typical Characteristics
SHUTDOWN CURRENT (µA)
97
96
95
94
93
92
91
2
6
8
10
1
0
12
0
2
4
6
8
10
4
6
8
10
Switch Frequency
vs. Temperature
EN Pin Bias Current
vs. Temperature
Schottky Forward
Voltage Drop
25
20
I = 4.2V
15 E N
I
EN
10
0.2
5 I = 3.0V
EN
0
-50
0
50
TEMPERATURE (°C)
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
SATURATION VOLTAGE (mV)
Schottky Reverse
Leakage Current
2
VR = 25V
1.5
1
VR = 16V
0.5
VR = 10V
40
50 60 70 80 90 100
TEMPERATURE (°C)
Switch Frequency
vs. Temperature
1.6
1.2
0.8
0.4
0
40
80
TEMPERATURE (°C)
120
= 3.6V
100
450
400
350
600
IS W = 500mA
0
40
80
TEMPERATURE (°C)
300
200
100
0
900
500
300
-40
400
SCHOTTKY FORWARD VOLTAGE DROP (mV)
Saturation Voltage
vs. Temperature
550
500
950
= 10V
1050
EN
850
0.4
I
30
12
600
750
IENABLE (µA)
0.6
35
700
650
50
1
M9999-070105
2
VIN (V)
0.8
0
-40
0
VIN (V)
40
2
1
0
12
45
2.5
2
VIN (V)
1.2
0
30
2
3
550
1.4
4
3
4
450
0
SATURATION VOLTAGE (mV)
SWITCHING FREQUENCY (MHz)
SCHOTTKY LEAKAGE CURRENT (µA)
SWITCHING FREQUENCY (MHz)
90
4
CURRENT LIMIT (mA)
FB VOLTAGE (mV)
98
Quiescent Current
vs. Input Voltage
5
QUIESCENT CURRENT (mA)
5
99
SCHOTTKY FORWARD CURRENT (mA)
100
Shutdown Current
vs. Input Voltage
1150
Feedback Voltage
vs. Input Voltage
120
Current Limit
vs. Temperature
850
800
750
700
650
V = 2.5V
IN
600
-40
0
40
80
TEMPERATURE (°C)
120
Switch Saturation Voltage
vs. Current
500
400
VIN = 2.5V
300
VIN = 5V
200
100
0
0
100
200 300
ISW (mA)
4
400
500
July, 2005
MIC2292/93
Micrel, Inc.
Functional Diagram
VIN
FB
EN
OUT
OVP*
SW
VREF
PWM
Generator
gm
95mV
S
1.6MHz
or
2.0MHz
Oscillator
Ramp
Generator
GND
MIC2292/93 Block Diagram
Functional Description
The gm error amplifier measures the LED current through the
external sense resistor and amplifies the error between the
detected signal and the 95mV reference voltage. The output
of the gm error amplifier provides the voltage-loop signal
that is fed to the other input of the PWM generator. When
the current-loop signal exceeds the voltage-loop signal, the
PWM generator turns off the bipolar output transistor. The
next clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control. The
LED is set by the feedback resistor:
95mv
ILED =
RFB
The MIC2292/93 is a constant frequency, PWM current mode
boost regulator. The block diagram is shown above. The
MIC2292/93 is composed of an oscillator, slope compensation
ramp generator, current amplifier, gm error amplifier, PWM
generator, 500mA bipolar output transistor, and Schottky
rectifier diode. The oscillator generates a 1.6MHz clock for the
MIC2292 and a 2.0MHz clock for the MIC2293. The clocks'
two functions are to trigger the PWM generator that turns on
the output transistor and to reset the slope compensation
ramp generator. The current amplifier is used to measure
the switch current by amplifying the voltage signal from the
internal sense resistor. The output of the current amplifier
is summed with the output of the slope compensation ramp
generator. This summed current-loop signal is fed to one of
the inputs of the PWM generator.
July 2005
The Enable pin shuts down the output switching and disables
control circuitry to reduce input current to leakage levels.
Enable pin input current is zero at zero volts.
5
M9999-070105
MIC2292/93
Micrel, Inc.
External Component Selection
tions. The table below shows recommended inductor and output capacitor values for various series-LED applications:
The MIC2292/93 can be used across a wide rage of applicaSeries LEDs
2
L
22µH
15µH
10µH
6.8µH
4.7µH
3
22µH
15µH
10µH
6.8µH
4.7µH
4
22µH
15µH
10µH
6.8µH
4.7µH
5, 6
22µH
15µH
10µH
6.8µH
4.7µH
7, 8
22µH
15µH
10µH
6.8µH
4.7µH
M9999-070105
Manufacturer
LQH32CN220K21 (Murata)
NLC453232T-220K(TDK)
LQH32CN150K21 (Murata)
NLC453232T-150K(TDK)
LQH32CN100K21 (Murata)
NLC453232T-100K(TDK)
LQH32CN6R8K21 (Murata)
NLC453232T-6R8K(TDK)
LQH32CN4R7K21 (Murata)
NLC453232T-4R7K(TDK)
LQH43MN220K21 (Murata)
NLC453232T-220K(TDK)
LQH43MN 150K21 (Murata)
NLC453232T-150K(TDK)
LQH43MN 100K21 (Murata)
NLC453232T-100K(TDK)
LQH43MN 6R8K21 (Murata)
NLC453232T-6R8K(TDK)
LQH43MN 4R7K21 (Murata)
NLC453232T-4R7K(TDK)
LQH43MN220K21 (Murata)
NLC453232T-220K(TDK)
LQH43MN 150K21 (Murata)
NLC453232T-150K(TDK)
LQH43MN 100K21 (Murata)
NLC453232T-100K(TDK)
LQH43MN 6R8K21 (Murata)
NLC453232T-6R8K(TDK)
LQH43MN 4R7K21 (Murata)
NLC453232T-4R7K(TDK)
LQH43MN220K21 (Murata)
NLC453232T-220K(TDK)
LQH43MN 150K21 (Murata)
NLC453232T-150K(TDK)
LQH43MN 100K21 (Murata)
NLC453232T-100K(TDK)
LQH43MN 6R8K21 (Murata)
NLC453232T-6R8K(TDK)
LQH43MN 4R7K21 (Murata)
NLC453232T-4R7K(TDK)
LQH43MN220K21 (Murata)
NLC453232T-220K(TDK)
LQH43MN 150K21 (Murata)
NLC453232T-150K(TDK)
LQH43MN 100K21 (Murata)
NLC453232T-100K(TDK)
LQH43MN 6R8K21 (Murata)
NLC453232T-6R8K(TDK)
LQH43MN 4R7K21 (Murata)
NLC453232T-4R7K(TDK)
6
Min COUT
2.2µF
1µF
0.22µF
0.22µF
0.22µF
2.2µF
1µF
0.22µF
0.22µF
0.27µF
1µF
1µF
0.27µF
0.27µF
0.27µF
0.22µF
0.22µF
0.27µF
0.27µF
0.27µF
0.22µF
0.22µF
0.27µF
0.27µF
0.27µF
Manufacturer
0805ZD225KAT(AVX)
GRM40X5R225K10(Murata)
0805ZD105KAT(AVX)
GRM40X5R105K10(Murata)
0805ZD224KAT(AVX)
GRM40X5R224K10(Murata)
0805ZD225KAT(AVX)
GRM40X5R225K10(Murata)
0805ZD224KAT(AVX)
GRM40X5R224K10(Murata)
0805YD225MAT(AVX)
GRM40X5R225K16(Murata)
0805YD105MAT(AVX)
GRM40X5R105K16(Murata)
0805YD224MAT(AVX)
GRM40X5R224K16(Murata)
0805YD224MAT(AVX)
GRM40X5R224K16(Murata)
0805YD274MAT(AVX)
GRM40X5R224K16(Murata)
0805YD105MAT(AVX)
GRM40X5R105K25(Murata)
0805YD105MAT(AVX)
GRM40X5R105K25(Murata)
0805YD274MAT(AVX)
GRM40X5R274K25(Murata)
0805YD274MAT(AVX)
GRM40X5R274K25(Murata)
0805YD274MAT(AVX)
GRM40X5R274K25(Murata)
08053D224MAT(AVX)
GRM40X5R224K25(Murata)
08053D224MAT(AVX)
GRM40X5R224K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
08053D224MAT(AVX)
GRM40X5R224K25(Murata)
08053D224MAT(AVX)
GRM40X5R224K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
08053D274MAT(AVX)
GRM40X5R274K25(Murata)
July, 2005
MIC2292/93
Micrel, Inc.
Dimming Control
There are two techniques for dimming control. One is PWM
dimming and the other is continuous dimming.
1. PWM dimming control is implemented by applying
a PWM signal on EN pin as shown in Figure 1.
The MIC2292/93 is turned on and off by the PWM
signal. With this method, the LEDs operate with
either zero or full current. The average LED current
is increased proportionally to the duty-cycle of the
PWM signal. This technique has high-efficiency
because the IC and the LEDs consume no current
during the off cycle of the PWM signal. Typical
frequency should be between 100Hz and 10kHz.
2. Continuous dimming control is implemented by
applying a DC control voltage to the FB pin of the
MIC2292/93 through a series resistor as shown in
Figure 2. The LED current is decreased proportionally with the amplitude of the control voltage. The
LED intensity (current) can be dynamically varied
applying a DC voltage to the FB pin. The DC voltage can come from a DAC signal or a filtered PWM
signal. The advantage of this approach is that a
high frequency PWM signal (>10kHz) can be used
to control LED intensity.
Open-Circuit Protection
If the LEDs are disconnected from the circuit, or in case
an LED fails open, the sense resistor will pull the FB pin to
ground. This will cause the MIC2292/93 to switch with a high
duty-cycle resulting in output overvoltage. This may cause
the SW pin voltage to exceed its maximum voltage rating,
possibly damaging the IC and the external components. To
ensure the highest level of protection, the MIC2292/93 has
three product options in the 8-lead MLF™with overvoltage
protection, OVP. The extra pins of the 8-leadMLF™ package
allow the use of a dedicated OVP monitor with options for
15V or 34V (see Figure 3). The reason for the three OVP
levels is to let users choose the suitable level of OVP for their
application. For example, a 3-LED application would typically
see an output voltage of no more than 12V, so a 15V OVP
option would offer a suitable level of protection. This allows
the user to select the output diode and capacitor with the
lowest voltage ratings, and accordingly, smallest size and
lowest cost. The OVP will clamp the output voltage to within
the specified limits.
VIN
VIN
VIN
SW
OUT
FB
EN
GND
VIN
SW
OUT
PWM
EN
GND
Figure 3. MLF™ Package OVP Circuit
FB
Start-Up and Inrush Current
During start-up, inrush current of approximately double the
nominal current flows to set up the inductor current and the
voltage on the output capacitor. If the inrush current needs
to be limited, a soft-start circuit similar to Figure 4 could be
implemented. The soft-start capacitor, Css, provides overdrive to the FB pin at start-up, resulting in gradual increase
of switch duty cycle and limited inrush current.
Figure 1. PWM Dimming Method
VIN
VIN
SW
OUT
EN
GND
FB
VIN
CSS
5.11k
49.9k
VIN
DC
Equivalent
2200pF
SW
OUT
EN
Figure 2. Continuous Dimming
GND
FB
R
10k
Figure 4. Soft-Start Circuit
July 2005
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M9999-070105
MIC2292/93
Micrel, Inc.
Functional Characteristics
6-Series LED Circuit without External Soft-Start
OUTPUT VOL AGE
INPUT CURRENT
ENABLE
(200mA/div)
(2V/div)
OUTPUT VOL AGE
INPUT CURRENT
ENABLE
(200mA/div)
(2V/div)
6-Series LED Circuit with External Soft-Start
L = 10µH
CIN = 1µF
COUT = 0.22µF
VIN = 3.6V
IOUT = 20mA
6 LEDs
CSS = 2200pF
R = 10kΩ
TIME (100µs/div.)
M9999-070105
L = 10µH
CIN = 1µF
COUT = 0.22µF
VIN = 3.6V
IOUT = 20mA
6 LEDs
TIME (100µs/div.)
8
July, 2005
MIC2292/93
Micrel, Inc.
Package Information
8-lead MLF™ (BML)
MICREL INC.
TEL
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
+ 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Inc.
July 2005
9
M9999-070105