Maxim MAX8607 1mhz pwm boost converter for 1.5a white led camera flash Datasheet

19-3783; Rev 1; 2/07
KIT
ATION
EVALU
LE
B
A
IL
A
AV
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
The MAX8607 white LED boost converter is optimized
for camera flash/strobe applications using high-current
white LEDs. The MAX8607 integrates a 1MHz PWM
boost converter, 1.5A low-dropout (LDO) current regulator, and logic control circuitry for a space-saving LED
flash design. Two logic inputs control four modes of
operation: shutdown mode reduces the quiescent current to 0.1µA (typ), movie mode supplies up to 360mA
of LED current for continuous lighting, flash mode supplies up to 1.5A of LED current for short-duration lighting during an exposure, and disco mode supplies +5V
(at up to 1A) to external circuits while driving the LED
with a fixed 80mA current.
The internal 1MHz boost converter features an adaptive
control scheme with an internal switching MOSFET and
synchronous rectifier to improve efficiency and minimize external component count. The MAX8607 is available in a 14-pin, 3mm x 3mm TDFN package (0.8mm
max height).
Features
♦ Supports Lumileds and Other High-Power
White LEDs
♦ Independently Set Flash/Movie Currents
Flash-Mode Current Up to 1.5A
Movie-Mode Current Up to 360mA
♦ Disco Mode with Fixed 5V (Up to 1A) and 80mA
LED Current
♦ 84% Efficiency (PLED / PBATT) at 1.1A
♦ TA Derating Function for LED Thermal Protection
♦ Output Overvoltage Protection (OVP)
♦ Soft-Start Eliminates Inrush Current
♦ 1MHz PWM Operation at All Loads
♦ Small External Components
♦ 2.7V to 5.5V Input Voltage Range
♦ 0.1µA Shutdown Mode
Applications
♦ 14-Pin, 3mm x 3mm TDFN Package
Ordering Information
Camera Flashes/Strobes
Cell Phones/Smartphones
PART*
PIN-PACKAGE
TOP MARK
MAX8607ETD+
14 TDFN 3mm x 3mm
(T1433-1)
ABA
PDAs and Digital Cameras
+Indicates lead-free package.
*The MAX8607ETD is characterized over the -40°C to +85°C
temperature range.
Typical Operating Circuit
Pin Configuration
OUT
LX
LX
PGND
PGND
LED
INPUT
2.7V TO 5.5V
OUTS
TOP VIEW
14
13
12
11
10
9
8
MAX8607
2.2µH
OUTPUT
LX
MAX8607 OUT
10µF
MODESELECT
INPUTS
OUTS
PGND
LGND
COMP
GND
10µF
UP TO 1.5A FLASH
UP TO 360mA MOVIE
EN1
EN2
LED
4
5
6
7
FLSH
GND
LGND
EN1
3
MOV
2
EN2
1
COMP
+
FLSH
MOV
TDFN
3mm x 3mm
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX8607
General Description
MAX8607
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
ABSOLUTE MAXIMUM RATINGS
OUT, OUTS, EN1, EN2 to GND ................................-0.3V to +6V
FLSH, MOV, LED, COMP, LX to GND ....-0.3V to (VOUTS + 0.3V)
LGND, PGND to GND. ..........................................-0.3V to +0.3V
LX Current. ........................................................................2ARMS
Continuous Power Dissipation (TA = +70°C)
14-Pin TDFN 3mm x 3mm (derate 18.2mW/°C
above +70°C)..............................................................1455mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10µF, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise
noted.) (Note 1)
PARAMETER
CONDITIONS
MIN
Supply Voltage
IC supplied from OUTS
2.7
Undervoltage-Lockout
Threshold
VOUTS rising, 100mV (typ) hysteresis
2.25
OUT Quiescent Current, Flash or Movie Mode
LX switching, ILED = 0mA
OUT Quiescent Current, Shutdown Mode
OUT Regulation Voltage
EN1 = EN2 = GND
TYP
2.38
MAX
UNITS
5.5
V
2.65
V
4
TA = +25°C
0.1
TA = +85°C
1
mA
1
Overvoltage limit, ILED = 0mA, VLED = 0V
5.3
5.5
5.7
VLED = 0.5V
3.65
3.85
3.95
Disco mode, ILED = 80mA
4.8
5.0
5.2
TA = +25°C
0.01
1
TA = +85°C
0.5
LED Current, Shutdown Mode
EN1 = EN2 = GND
Current-Source Guaranteed Sink Current
RMOV = 2kΩ,
RFLSH = 2kΩ,
VLED = 0.5V
Current-Source Multiplier in MOV Mode
(ILED / IMOV)
IMOV up to 300µA
Current-Source Accuracy in MOV Mode
RMOV = 2kΩ,
VLED = 0.5V
MOV Current-Source Dropout Voltage
RMOV = 2kΩ
Disco Current-Source Current Setting
VEN1 = 0V, VEN2 = 5V
Current-Source Multiplier in FLSH Mode
(ILED / IFLSH)
IFLSH up to 300µA
Current-Source Accuracy in FLSH Mode
FLSH Current-Source Dropout Voltage
Flash mode
1200
1500
Movie mode
338
360
Disco mode
µA
V
µA
mA
80
1200
A/A
TA ≥ 0°C (Note 2)
-3
±0.5
+3
TA = -40°C
-6
±0.5
+6
48
100
mV
80
108
mA
62
%
5000
A/A
RFLSH = 2kΩ, VLED = 0.5V, TA ≥ -40°C
(Note 2)
±3
%
RFLSH = 2kΩ
200
420
mV
LX n-Channel Current Limit
4.4
A
MOV Regulation Voltage
600
mV
FLSH Regulation Voltage
600
mV
60
µS
LED to COMP Transconductance
2
VCOMP = 1.5V
_______________________________________________________________________________________
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
(VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10µF, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise
noted.) (Note 1)
TYP
MAX
UNITS
COMP Input Resistance to GND
PARAMETER
During shutdown or UVLO
CONDITIONS
MIN
140
250
Ω
LED TA Derating Function Threshold
Temperature when the LED current derating
function begins
+40
°C
LED TA Derating Function Slope
TA = +40°C to +85°C
-1.67
%/°C
EN1 and EN2 Logic-High Input Voltage
VOUTS = 2.7V to 5.5V
EN1 and EN2 Logic-Low Input Voltage
VOUTS = 2.7V to 5.5V
EN1 and EN2 Logic Input Bias Current
VEN_ = 5.5V
1.4
V
0.4
TA = +25°C
0.01
TA = +85°C
0.03
1
V
µA
LX n-Channel On-Resistance
ILX = 200mA
50
100
mΩ
LX p-Channel On-Resistance
ILX = 200mA
100
200
mΩ
LX Leakage
VLX = 5.5V
TA = +25°C
0.01
1
TA = +85°C
0.03
Operating Frequency
0.8
1.0
Maximum Duty Cycle
65
75
Minimum Duty Cycle
µA
1.2
MHz
8
%
%
4
Note 1: All devices are production tested at TA = +25°C. Specifications over temperature are guaranteed by design and characterization and not production tested.
Note 2: For temperatures below the thermal derating start point.
Typical Operating Characteristics
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25°C, unless otherwise noted.)
RFLSH = 4.02kΩ
2000
1500
RFLSH = 8.06kΩ
1000
94
400
RMOV = 3.57kΩ
200
RMOV = 6.49kΩ
92
90
88
86
84
100
500
96
RMOV = 2.00kΩ
300
INCLUDES 83mA LED CURRENT
98
EFFICIENCY (%)
RFLSH = 3.01kΩ
2500
100
MAX8607toc02
RFLSH = 2kΩ
3000
500
BATTERY CURRENT (mA)
BATTERY CURRENT (mA)
3500
600
MAX8607toc01
4000
BOOST CONVERTER EFFICIENCY
vs. LOAD CURRENT (DISCO MODE)
MOVIE-MODE BATTERY CURRENT
vs. INPUT VOLTAGE
MAX8607toc03
FLASH-MODE BATTERY CURRENT
vs. INPUT VOLTAGE
82
0
80
0
2.7
3.1
3.5
3.9
4.7
4.3
INPUT VOLTAGE (V)
5.1
5.5
2.7
3.1
3.5
3.9
4.7
4.3
INPUT VOLTAGE (V)
5.1
5.5
10
100
1000
LOAD CURRENT (mA)
_______________________________________________________________________________________
3
MAX8607
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25°C, unless otherwise noted.)
IC SUPPLY CURRENT
vs. INPUT VOLTAGE
1000
MAX8607toc04
400
350
DISCO MODE
900
FLASH MODE
800
SUPPLY CURRENT (µA)
300
250
200
150
100
MAX8607toc05
LED CURRENT
vs. AMBIENT TEMPERATURE
LED CURRENT (mA)
MAX8607
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
700
600
500
MOVIE MODE
400
300
200
50
100
0
0
-40
-20
0
20
60
40
AMBIENT TEMPERATURE (°C)
80
2.7
SWITCHING WAVEFORMS
(MOVIE MODE)
3.5
3.9 4.3
4.7
INPUT VOLTAGE (V)
5.1
5.5
SOFT-START RESPONSE
(STANDBY TO MOVIE-MODE TRANSITION)
MAX8607toc06
MAX8607toc07
20mV/div
VIN
3.1
VEN1
0V 5V/div
200mA/div
VOUT
IL
10mV/div
ILED
0A
100mA/div
IIN
0A
5V/div
VLX
100mA/div
2V/div
VOUT
0V
400ns/div
100µs/div
LOAD TRANSIENT
(DISCO MODE)
SOFT-START RESPONSE
(MOVIE-MODE TO FLASH TRANSITION)
MAX8607toc09
MAX8607toc08
700mA
5V/div
VEN2
100mA
IL0AD
ILED
200mA/div
IIN
0A 500mA/div
500mV/div
VOUT(RIPPLE)
0A
2V/div
VOUT
0V
400µs/div
4
2ms/div
_______________________________________________________________________________________
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
MOVIE-MODE LED CURRENT
vs. MOV RESISTANCE
350
1400
1200
LED CURRENT (mA)
300
LED CURRENT (mA)
MAX8607toc11
1600
MAX8607toc10
400
FLASH-MODE LED CURRENT
vs. FLSH RESISTANCE
250
200
150
100
50
1000
800
600
400
200
0
0
1
10
1
100
RMOV (kΩ)
10
100
RFLSH (kΩ)
Pin Description
PIN
NAME
FUNCTION
1
COMP
2
EN1
Enable Input 1. EN1 and EN2 set the operating mode (see Table 1).
3
EN2
Enable Input 2. EN1 and EN2 set the operating mode (see Table 1).
4
MOV
Movie Current Program Input. Connect a resistor from MOV to GND to set the LED current in movie mode.
RMOV must be greater than 2kΩ.
5
FLSH
Flash Current Program Input. Connect a resistor from FLSH to GND to set the LED current in flash mode.
RFLSH must be greater than 2kΩ.
6
GND
Analog Ground. Connect GND to the exposed paddle directly under the IC.
7
LGND
8
LED
9, 10
PGND
11, 12
LX
Inductor Connection. Connect LX to the switched side of the inductor. LX is internally connected to the
drains of the internal MOSFETs. Both MOSFETs are off during shutdown.
13
OUT
Regulator Output. Connect OUT to the anode of the external LED. Bypass OUT to PGND with a 10µF or
larger ceramic capacitor. During shutdown, OUT is one body-diode drop below the input voltage.
14
OUTS
Output Sense and IC Supply Input. Connect OUTS to OUT at the output bypass capacitor. The IC’s operating
power is supplied from OUTS.
—
EP
Compensation Input. Connect a 0.1µF ceramic capacitor from COMP to GND for regulator stability.
LED Current Regulator Ground. Connect LGND to the ground plane on the PC board.
LED Current Regulator. Connect LED to the cathode of the external LED. LED is high impedance during shutdown.
Power Ground. Connect PGND to the input capacitor ground. Also, connect PGND to the PC board ground plane.
Exposed Paddle. Connect the exposed paddle to GND directly under the IC and to a large PC board
ground plane for increased thermal performance.
_______________________________________________________________________________________
5
MAX8607
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25°C, unless otherwise noted.)
MAX8607
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
LX
OUT
REF
OUTS
FORCED-PWM
BOOST CONTROL
PGND
1MHz
CLOCK
FEEDBACK
SELECT
COMP
1.25V
EN1
SHUTDOWN AND
MODE CONTROL
LED
EN2
LDO
REGULATOR
FLSH
MOV
GND
MAX8607
LGND
Figure 1. Functional Diagram
Detailed Description
Boost Converter
The MAX8607 includes a fixed-frequency, PWM boost
converter that supplies the LED current. The output
voltage is adaptively controlled to provide adequate
headroom with varying LED forward voltage. The boost
converter switches an internal power MOSFET and synchronous rectifier at a constant 1MHz frequency with
varying duty cycle up to 75% to maintain constant LED
current over the 2.7V to 5.5V input range. Internal special circuits prevent any unwanted subharmonic switching in the critical buck/boost region.
6
LDO Current Regulator (LED)
A low-dropout (LDO) linear current regulator from LED
to LGND sinks current from the external LED’s cathode
terminal. The LED current is regulated to a user-programmable level. In movie mode, the current into LED
is regulated to 1200 times the current set by the MOV
resistor (RMOV). In flash mode, the current into LED is
regulated to 5000 times the current set by the FLSH
resistor (RFLSH). In disco mode, the current into LED is
regulated to 80mA.
_______________________________________________________________________________________
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
Drive EN1 and EN2 low to place the IC into a lowpower shutdown mode. See the Shutdown section for
more details.
Overvoltage Protection
The output voltage of the MAX8607 is limited by internal
overvoltage-protection (OVP) circuitry, which prevents
the output from exceeding 5.7V under any conditions.
In flash and movie modes, if the output voltage nears
5.5V, the LED current is smoothly reduced through proprietary means to prevent overvoltage without sudden
termination of the output current. In case of an LED with
very high forward voltage (V F), this circuit provides
more reliable and repeatable flash than would a simple
on/off comparator. In disco mode, the output is limited
by the internal 5.0V regulation.
Undervoltage Lockout
The MAX8607 contains undervoltage-lockout (UVLO)
circuitry that disables the IC until VOUTS is greater than
2.38V. Prior to startup, VOUTS is one diode drop below
the input voltage. This ensures a great enough input
voltage for startup.
Soft-Start
The MAX8607 attains soft-start by charging C COMP
with a 100µA current source. During this time, the internal MOSFET is switching at the minimum duty cycle.
Once VCOMP rises above 1V, the duty cycle increases
until output reaches the desired regulation level. COMP
is pulled to GND with a 140Ω internal resistor during
UVLO, OVP, or shutdown. See the Typical Operating
Characteristics for an example of soft-start operation.
Table 1. EN1 and EN2 Mode Selection
EN1
EN2
0
0
Shutdown
MODE
0
1
Disco Mode
1
0
Movie Mode
1
1
Flash Mode
Shutdown
Drive EN1 and EN2 low to place the MAX8607 into a
low-power shutdown mode. In shutdown, supply current is reduced to 0.1µA (typ). CCOMP is discharged
during shutdown, allowing the device to reinitiate softstart when it is enabled. The internal MOSFET and synchronous rectifier are turned off during shutdown;
however, OUT is one body-diode drop below the input.
LED is high impedance so the external LED is off, but
any external circuitry on OUT is not disconnected and,
therefore, should include its own shutdown capability.
Typical shutdown timing characteristics are shown in
the Typical Operating Characteristics.
Ambient Temperature Derating Function
The MAX8607 limits the maximum LED current depending on its die temperature. Once the die temperature
reaches +40°C, the LED current decreases by 1.67%
per °C. This corresponds to approximately 0mA of LED
current at +100°C. Due to the package’s exposed paddle, the die temperature is very close to the PC board
temperature. The temperature derating function allows
the LED current to be safely set higher at normal operating temperatures, thereby allowing either a brighter
flash or movie light to be used for normal ambient temperatures. See the Typical Operating Characteristics
for a graph of LED Current vs. Ambient Temperature.
Applications Information
Setting the Movie-Mode Current
To set the LED current during movie mode, connect a
resistor from MOV to GND (RMOV). VMOV is regulated
to 0.6V and the current through RMOV is mirrored to
LED with a gain of 1200. RMOV is calculated as:
RMOV = (0.6V x 1200) / ILED(MOV)
Setting the Flash-Mode Current
To set the LED current during flash mode, connect a
resistor from FLSH to GND (RFLSH). VFLSH is regulated
to 0.6V and the current through RFLSH is mirrored to
LED with a gain of 5000. RFLSH is calculated as:
RFLSH = (0.6V x 5000) / ILED(FLSH)
_______________________________________________________________________________________
7
MAX8607
Mode-Select Inputs (EN1, EN2)
Drive EN1 high and EN2 low to enable movie mode. In
this mode, the current regulator regulates the current
through the LED to 1200 times the current set by the
MOV resistor. See the Setting the Movie-Mode Current
section for details on setting the movie-mode current.
Drive EN1 and EN2 high to enable flash mode. In this
mode, the current through the LED is regulated to 5000
times the current set by the FLSH resistor. See the
Setting the Flash-Mode Current section for details on setting the flash-mode current. The time duration of the flash
mode must be set using external circuitry or software.
Drive EN1 low and EN2 high to enable disco mode. In
this mode, the output of the boost converter provides a
regulated +5V at up to 1A for external circuitry, while
the LED current is regulated to 80mA. The LED current
is not adjustable in this mode.
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
MAX8607
Capacitor Selection
L1
INPUT
2.7V TO 5.5V 2.2µH
C1
10µF
11, 12
9, 10
C3
0.1µF
LX
MAX8607
U1
OUTS
3
C2
10µF
14
D1
1
2
13
PGND
COMP
MODESELECT
INPUTS
OUT
LGND
GND
EN1
EN2
FLSH
5
R1
MOV
4
LED
EP
7
6
8
PC Board Layout
R2
Figure 2. Typical Application Circuit
Inductor Selection
The MAX8607 is designed to use a 2.2µH inductor. To
prevent core saturation, ensure that the inductor-saturation current rating exceeds the peak inductor current
for the application. Calculate the worst-case peak
inductor current with the following formula:
IPEAK =
5V × ILED(MAX)
0.9 × VIN(MIN)
+
Bypass the input to PGND using a ceramic capacitor.
Place the capacitor as close to the IC as possible. The
exact value of the input capacitor is not critical. The
typical value for the input capacitor is 10µF; however,
larger value capacitors can be used to reduce input
ripple at the expense of size and higher cost.
The output capacitance required depends on the
required LED current. A 10µF ceramic capacitor works
well in most situations, but a 4.7µF capacitor is acceptable for load current below 300mA.
Due to fast switching waveforms and high-current paths,
careful PC board layout is required. Connect GND
directly to the exposed paddle underneath the IC; connect the exposed paddle to the PC board ground plane.
Connect LGND and PGND to the ground plane. The output bypass capacitor should be placed as close to the
IC as possible. C COMP should be connected from
COMP to GND as close to the IC as possible. Minimize
trace lengths between the IC and the inductor, the input
capacitor, and the output capacitor; keep these traces
short, direct, and wide. The ground connections of CIN
and COUT should be as close together as possible and
connected to PGND. The traces from the input to the
inductor and from the output capacitor to the LED may
be longer. A sample layout is available in the MAX8607
evaluation kit (MAX8607EVKIT) to speed design.
VIN(MIN) × 0.5µs
2 × 2.2µH
Chip Information
PROCESS: BiCMOS
Table 2 provides a list of suggested inductors.
Table 2. Suggested Inductors
MANUFACTURER
Coilcraft
Cooper (Coiltronics)
FDK
TOKO
8
SERIES
INDUCTANCE
(µH)
DCR
(mΩ)
ISAT
(A)
DIMENSIONS
(LTYP x WTYP x HMAX = Volume)
LPO3310
2.2
150
1.1
3.3 x 3.3 x 1.0 = 11mm3
SD3114
2.2
83
1.48
3.0 x 3.0 x 1.45 = 13mm3
MIPF2520
2.2
80
0.7
2.5 x 2.0 x 1.0 = 5mm3
MIPW3226
2.2
100
1.1
3.2 x 2.6 x 1.0 = 8mm3
DE2812C
2.2
70
1.6
3.0 x 2.8 x 1.2 = 10mm3
FDSE0312
2.2
160
2.3
3.0 x 3.0 x 1.2 = 11mm3
_______________________________________________________________________________________
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
6, 8, &10L, DFN THIN.EPS
_______________________________________________________________________________________
9
MAX8607
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MAX8607
1MHz PWM Boost Converter for 1.5A
White LED Camera Flash
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
COMMON DIMENSIONS
PACKAGE VARIATIONS
SYMBOL
MIN.
MAX.
PKG. CODE
N
D2
E2
e
JEDEC SPEC
b
[(N/2)-1] x e
A
0.70
0.80
T633-2
6
1.50±0.10
2.30±0.10
0.95 BSC
MO229 / WEEA
0.40±0.05
1.90 REF
D
2.90
3.10
T833-2
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
E
2.90
3.10
T833-3
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
A1
0.00
0.05
T1033-1
10
1.50±0.10
2.30±0.10
0.50 BSC
MO229 / WEED-3
0.25±0.05
2.00 REF
L
0.20
0.40
T1033-2
10
1.50±0.10
2.30±0.10
0.50 BSC
MO229 / WEED-3
0.25±0.05
2.00 REF
k
0.25 MIN.
T1433-1
14
1.70±0.10
2.30±0.10
0.40 BSC
----
0.20±0.05
2.40 REF
A2
0.20 REF.
T1433-2
14
1.70±0.10
2.30±0.10
0.40 BSC
----
0.20±0.05
2.40 REF
Revision History
Pages changed at Rev 1: 1, 2, 9, 10
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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