MICREL MIC2293C

MIC2292/93C
High Frequency PWM White LED Drivers
with Internal Schottky Diode and OVP
General Description
Features
The MIC2292C and MIC2293C are high frequency, Pulse
Width Modulator (PWM) boost regulators optimized for
constant-current, white LED driver applications. Because
of their constant PWM switching frequencies of 1.6MHz
and 2MHz, respectively, the MIC2292/93C 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 MIC2292/3C allows
direct operation from 1- and 2-cell Li Ion as well as 3- to 4cell NiCad/NiMH/Alkaline batteries. The MIC2292/3C products are available in a small size 8-pin 2mm × 2mm MLF®
package and have a junction temperature range of
–40°C to +125°C.
Data sheets and 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 (MIC2292C)
2.0MHz PWM operation (MIC2293C)
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-pin 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
MIC2293C-15BML
MIC2292C-15BML
VIN
Li Ion
1µF
VIN
SW
OUT
FB
EN
95mV
0.22µF
16V
Li Ion
1µF
SW
OUT
FB
EN
95mV
0.22µF
16V
GND
GND
1.6MHz PWM White LED Driver with 15V OVP
2MHz PWM White LED Driver with 15V OVP
MLF and MicroLeadFrame are registered 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
September 2006
1
M9999-090706
Micrel, Inc.
MIC2292/93C
Ordering Information
Marking
Code
Part Number
Overoltage
Protection
Junction
Temp. Range
Package
15V
–40°C to +125°C
8-Pin 2mm x 2mm MLF®
–40°C to +125°C
8-Pin 2mm x 2mm MLF
®
Pb-Free
8-Pin 2mm x 2mm MLF
®
Standard
®
MIC2292C-15BML
MIC2292C-15YML
15V
MIC2292C-34BML
34V
–40°C to +125°C
Lead Finish
Standard
MIC2292C-34YML
34V
–40°C to +125°C
8-Pin 2mm x 2mm MLF
MIC2293C-15BML
15V
–40°C to +125°C
8-Pin 2mm x 2mm MLF®
Standard
MIC2293C-15YML
15V
–40°C to +125°C
8-Pin 2mm x 2mm MLF®
Pb-Free
®
MIC2293C-34BML
34V
–40°C to +125°C
8-Pin 2mm x 2mm MLF
MIC2293C-34YML
34V
–40°C to +125°C
8-Pin 2mm x 2mm MLF®
Pb-Free
Standard
Pb-Free
Pin Configuration
Denotes Pb-Free
OUT
1
8
PGND
VIN
2
7
SW
EN
3
6
FB
AGND
4
5
NC
EP
???
Denotes MIC2292/93C
®
8-Pin MLF (ML)
(Top View)
Fused Lead Frame
Pin Description
Pin Number
Pin Name
1
OUT
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.
4
AGND
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.
8
PGND
EP
GND
September 2006
Pin Name
Analog ground.
Power ground.
Ground (Return): Exposed backside pad.
2
M9999-090706
Micrel, Inc.
MIC2292/93C
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) .......................................................12V
Switch Voltage (VSW)....................................... –0.3V to 34V
Enable Pin Voltage (VEN)................................... –0.3V to VIN
FB Voltage (VFB)...............................................................6V
Switch Current (ISW) .........................................................2A
Ambient Storage Temperature (Ts) ...........–65°C to +150°C
Schottky Reverse Voltage (VDA).....................................34V
EDS Rating(3) .................................................................. 2kV
Supply Voltage (VIN)........................................ 2.5V to +10V
Output Voltage (VIN) ............................................ VIN to VOVP
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
2mm x 2mm MLF® (θJA).....................................93°C/W
Electrical Characteristics(4)
TA = 25°C, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 20mA, unless otherwise noted. Bold values indicate –40°C< TJ < +125°C.
Symbol
Parameter
Condition
Min
VIN
Supply Voltage Range
2.5
VUVLO
Under Voltage Lockout
1.8
Typ
2.1
Max
Units
10
V
2.4
V
IVIN
Quiescent Current
VFB > 200mV, (not switching)
2.5
5
mA
ISD
Shutdown Current
VEN = 0V(5)
0.1
1
µA
VFB
Feedback Voltage
(±10%)
95
105
mV
IFB
85
Feedback Input Current
VFB = 95mV
–450
nA
Line Regulation(6)
3V ≤ VIN ≤ 5V
0.5
%
5mA ≤ IOUT ≤ 20mA
0.5
%
90
%
Load Regulation
(6)
DMAX
Maximum Duty Cycle
ISW
Switch Current Limit
750
mA
VSW
Switch Saturation Voltage
ISW = 0.5A
450
mV
ISW
Switch Leakage Current
VEN = 0V, VSW = 10V
0.01
VEN
Enable Threshold
TURN ON
TURN OFF
85
IEN
Enable Pin Current
VEN = 10V
fSW
Oscillator Frequency
MIC2292C
MIC2293C
VD
Schottky Forward Drop
ID = 150mA
IRD
Schottky Leakage Current
VR = 30V
VOVP
Overvoltage Protection
MIC2292/93C-15
MIC2292/93C-34
TJ
Overtemperature
Threshold Shutdown
5
µA
0.4
V
V
20
40
µA
1.6
2.0
1.8
2.25
MHz
MHz
0.8
1
V
4
µA
14
32
16.5
37
V
V
1.5
1.4
1.75
11.4
27
150
10
Hysteresis
°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. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model.
4. Specification for packaged product only.
5. ISD = IVIN.
6. Guaranteed by design
September 2006
3
M9999-090706
Micrel, Inc.
MIC2292/93C
Typical Characteristics
95
94
93
92
91
8
10
0
12
0
2
4
Switch Frequency
vs. Temperature
50
45
40
1.2
IENABLE (µA)
1.0
0.8
0.6
0.4
0.2
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Schottky Reverse
Leakage Current
2
VR = 25V
1.5
1
VR = 16V
0.5
VR = 10V
0
30
2
40
50 60 70 80 90 100
TEMPERATURE (°C)
Switch Frequency
vs. Temperature
1.2
0.8
0.4
0
40
80
TEMPERATURE (°C)
September 2006
0
2
4
120
EN Pin Bias Current
vs. Temperature
100
700
8
10
12
500
400
300
200
100
0
SCHOTTKY FORWARD VOLTAGE DROP (mV)
900
500
450
400
350
IS W = 500mA
0
40
80
TEMPERATURE (°C)
Schottky Forward
Voltage Drop
600
Saturation Voltage
vs. Temperature
300
-40
6
VIN (V)
I = 3.6V
EN
10
5 I = 3.0V
EN
0
-50
0
50
TEMPERATURE (°C)
600
1.6
0
-40
0
12
35
I = 10V
30 E N
25
20
I = 4.2V
15 E N
550
SATURATION VOLTAGE (mV)
2.5
10
CURRENT LIMIT (mA)
1.4
8
VIN (V)
SATURATION VOLTAGE (mV)
SWITCHING FREQUENCY (MHz)
SCHOTTKY LEAKAGE CURRENT (µA)
SWITCHING FREQUENCY (MHz)
VIN (V)
6
750
6
1
650
4
2
550
2
1
3
450
0
2
SCHOTTKY FORWARD CURRENT (mA)
90
3
4
1150
96
4
1050
97
950
98
Quiescent Current
vs. Input Current
5
QUIESCENT CURRENT (mA)
5
SHUTDOWN CURRENT (µA)
FB VOLTAGE (mV)
100
99
Shutdown Voltage
vs. Input Voltage
850
Feedback Voltage
vs. Input Voltage
120
Current Limit
vs. Temperature
850
800
750
700
650
VIN = 2.5V
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
M9999-090706
Micrel, Inc.
MIC2292/93C
Functional Characteristics
September 2006
6-Series LED Circuit without External Soft-Start
OUTPUT VOLTAGE
INPUT CURRENT
ENABLE
(200mA/div)
(2V/div)
OUTPUT VOLTAGE
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
5
L = 10µH
CIN = 1µF
COUT = 0.22µF
VIN = 3.6V
IOUT = 20mA
6 LEDs
M9999-090706
Micrel, Inc.
MIC2292/93C
Functional Diagram
VIN
FB
EN
OUT
OVP
SW
PWM
Generator
gm
VREF
95mV
S
1.6MHz
or
2.0MHz
Oscillator
GND
Ramp
Generator
MIC2292/93C Block Diagram
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:
Functional Description
The MIC2292/93C is a constant frequency, PWM current
mode boost regulator. The block diagram is shown
above. The MIC2292/93C 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 MIC2292C
and a 2.0MHz clock for the MIC2293C. 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.
September 2006
ILED =
95mW
R FB
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.
6
M9999-090706
Micrel, Inc.
MIC2292/93C
inductor and output capacitor values for various seriesLED applications.
External Component Selection
The MIC2292/93C can be used across a wide rage of
applications. The table below shows recommended
Series 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
September 2006
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)
7
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)
M9999-090706
Micrel, Inc.
MIC2292/93C
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 MIC2292/93C 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 MIC2292/93C 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 MIC2292/93C 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 MIC2292/93C has three product options
in the 8-pin MLF® with overvoltage protection, OVP. The
extra pins of the 8-pin MLF® 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
EN
PWM
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 over-drive to the FB pin at start-up,
resulting in gradual increase of switch duty cycle and
limited inrush current.
GND
Figure 1. PWM Dimming Method
VIN
VIN
VIN
SW
CSS
2200pF
OUT
FB
EN
GND
5.11k
VIN
49.9k
SW
OUT
EN
DC
Equivalent
GND
FB
R
10k
Figure 2. Continuous Dimming
Figure 4. One of Soft-Start Circuit
September 2006
8
M9999-090706
Micrel, Inc.
MIC2292/93C
Package Information
8-Pin MLF® (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The 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.
© 2006 Micrel, Incorporated.
September 2006
9
M9999-090706