MIC2870
1.5A Synchronous Boost Flash LED Driver
with I
2
C Interface
General Description
The MIC2870 is a high-current, high-efficiency flash LED
driver for one or two high-brightness camera flash LEDs.
The LED driver current is generated by an integrated
inductive boost converter with 2MHz switching frequency
which allows the use of a very-small inductor and output
capacitor. These features make the MIC2870 an ideal
solution for high-resolution camera phone LED flashlight
driver applications.
MIC2870 supports two 750mA white-LEDs (WLEDs) or a
single 1.5A WLED configuration. When two WLEDs are
connected, their currents are matched automatically.
MIC2870 operates in either flash or torch modes that can
2
be controlled through either an I C interface or external
pins. The brightness in the flash and torch mode can be
adjusted via two external resistors individually. High-speed
2
mode I C interface provides a simple control at a clock
speed up to 3.4MHz to support most camera functions
such as auto-focus, white balance, and image capture
(flash mode).
The MIC2870 is available in 16-pin, 2mm × 2mm TQFN
package with a junction temperature range of
−40°C
to
+125°C.
Datasheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Features
•
Up to 1.5A flash LED driving current
−
2.7V to 5.0V input voltage range
•
High-efficiency 2MHz V
F
adaptive boost driver
•
Configurable 1 or 2 channel(s) WLED driver
•
LED driving current soft-start
2
•
Control through I C interface or external pins
•
Flash inhibit function for GSM pulse synchronization
•
True load disconnect
•
Flash time-out protection
•
1µA shutdown current
•
Available in 16-pin 2mm × 2mm TQFN package
Applications
•
•
•
•
•
•
Camera phones/mobile handsets
Cellular phones/smart phones
LED light for image capture/auto focus/white balance
Handset video light (torch light)
Digital cameras
Portable applications
Typical Application
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 5, 2013
Revision 1.0
Micrel, Inc.
MIC2870
Ordering Information
Part Number
MIC2870YFT
Note:
1. Package is a GREEN, RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
2. Thin QFN pin 1 identifier = “
▲
”.
Marking
70H
Temperature Range
–40°C to +125°C
Package
(1)
Lead Finish
NiPdAu
16-Pin 2mm × 2mm TQFN
Pin Configuration
16-Pin 2mm × 2mm TQFN
(Top View)
Pin Description
Pin Number
1
2
Pin Name
SCL
VIN
Pin Function
High-Speed Mode (3.4MHz) I²C Clock Input.
Supply Input. Connect a low-ESR ceramic capacitor of at least 4.7µF to PGND. A small capacitor
of 100nF between VIN and AGND is highly recommended.
Flash-Mode Enable Pin. A LOW-to-HIGH transition initiates the flash mode and flash-mode timer.
If FEN is left floating, it is pulled-down internally by a built-in 1µA current source when the device
is enabled.
Flash Inhibit. When FI is pulled HIGH, both LED currents are changed from the flash-mode
current level to the torch-mode current level. If FI is left floating, it is pulled-down internally by a
built-in 1µA current source when the device is enabled. This function is generally used to reduce
instantaneous battery load current by synchronizing with the handset’s GSM pulse off time.
Flash-Mode Current Level Programming. Connect a resistor from FRSET to AGND to set the
maximum current in the flash mode. For example, a 10kΩ resistor sets the LED sink current to its
maximum value of 750mA per channel. FRSET can be grounded if the default maximum flash-
mode current (750mA) is desired. FRSET, however, cannot be left floating and the maximum
resistance is limited to 80kΩ
Analog Ground. Reference ground for FRSET and TRSET pins.
3
FEN
4
FI
5
FRSET
6
AGND
September 5, 2013
2
Revision 1.0
Micrel, Inc.
MIC2870
Pin Description (Continued)
Pin Number
7, 15
Pin Name
PGND
Pin Function
Power Ground. PGND is used for the switching NMOS and PMOS of boost converter, and power
ground for LED current sinks.
Torch-Mode Current Level Programming. Connect a resistor from TRSET to AGND to set the
maximum current in the torch mode. For example, a 10kΩ resistor sets the LED sink current to its
maximum value of 187.5mA per channel. TRSET can be grounded if the default maximum torch-
mode current (187.5mA) is desired. TRSET, however, cannot be left floating and the maximum
resistance is limited to 80kΩ.
Channel 2 LED Current Sink. Connect the LED anode to OUT and cathode to LED2.
Channel 1 LED Current Sink. Connect the LED anode to OUT and cathode to LED1.
Torch-Mode Enable. Initiates torch mode when TEN is HIGH. If TEN is left floating, it is pulled-
down internally by a built-in 1µA current source when the device is enabled.
Boost Converter Output.
Enable (IC). The MIC2870 is in standby mode when EN is asserted HIGH. If EN is driven low for
2
more than 1s, the IC is shut down. Alternatively, the I C interface can be used for
enabling/disabling the IC through the master control/status register. EN is pulled down by an
internal resistor.
Inductor Connection. It is connected to the internal power MOSFETs.
High-Speed Mode (3.4MHz) I²C Data Input/Output.
Exposed Heat Sink Pad. Connect to PGND ground plane for best thermal performance. This pin
is internally connected to PGND.
8
TRSET
9
10
11
12
LED2
LED1
TEN
OUT
13
EN
14
16
EP
SW
SDA
ePad
September 5, 2013
3
Revision 1.0
Micrel, Inc.
MIC2870
Absolute Maximum Ratings
(3)
Supply Voltage (V
IN
) .....................................
−0.3V
to +6.0V
Enable Input Voltage
(V
EN
, V
FEN
, V
FI
, V
TEN
) .......................
−0.3V
to V
IN
+ 0.3V
V
OUT
, V
LED1
, and V
LED2
....................................
−0.3V
to 6.0V
2
I C I/O (V
SCL
, V
SDA
) ................................
−0.3V
to V
IN
+ 0.3V
V
FRSET
and V
TRSET
..................................
−0.3V
to V
IN
+ 0.3V
V
SW
.................................................................
−0.3V
to 6.0V
(5)
Power Dissipation (P
DISS
) ....................... Internally Limited
Lead Temperature (soldering, 10s) .......................... +260°C
Junction Temperature (T
J
) ........................
−40°C
to +150°C
Storage Temperature (T
S
) .........................
−40°C
to +150°C
(6)
ESD Rating ................................. 2kV HBM and 150V MM
Operating Ratings
(4)
Supply Voltage (V
IN
) ..................................... +2.7V to +5.0V
Enable Input Voltage (V
EN
, V
FEN
, V
FI
, V
TEN
) ............ 0V to V
IN
2
I C I/O (V
SCL
, V
SDA
) ................................................. 0V to V
IN
Junction Temperature (T
J
) ..........................
−40°C
to 125°C
(5)
Package Thermal Resistance
2mm × 2mm TQFN (θ
JA
) .................................... 80°C/W
Electrical Characteristics
(7)
V
IN
= 3.6V; L = 1μH, C
OUT
= 2.2μF, R
FRSET
= 10kΩ, R
TRSET
= 10kΩ, I
LED
= 100mA; T
A
= 25°C,
bold
values indicate
−40°C
≤ T
J
≤ 125°C,
unless otherwise noted.
Symbol
Power Supply
V
IN
I
VIN
I
VIN(SD)
I
SW(SD)
UVLO_Rise
UVLO_Hyst
V
OUT
Input Voltage
Quiescent Current
Shutdown Current
SW Pin Shutdown Current
UVLO Threshold (Rising)
UVLO Hysteresis
Output Voltage
Overvoltage Protection
Threshold
V
OVP
Overvoltage Protection
Hysteresis
OVP Blanking Time
D
MAX
D
MIN
I
SW_OC
Notes:
3. Exceeding the absolute maximum ratings may damage the device.
4. The device is not guaranteed to function outside its operating ratings.
5. The maximum allowable power dissipation of any T
A
(ambient temperature) is P
DISS(max)
= (T
J(max)
– T
A
) / θ
JA
. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
6. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.
7. Specification for packaged product only
Parameter
Condition
Min.
Typ.
Max.
Units
2.7
V
LED1
= V
LED2
> 200mV, not switching
V
LED1
= V
LED2
= 70mV, boost keeps switching
V
EN
= 0 V
V
EN
= 0 V
2.35
V
IN
≥ V
OUT
V
OUT
> V
IN
V
OUT
> V
IN
5.26
5.38
60
24
80
85
5.5
V
IN
= V
OUT
= 2.7V
3.35
4.5
0.9
4.2
0.6
1
2.5
300
5.0
V
mA
µA
5
2.65
µA
V
mV
V
IN
5.2
5.6
V
V
mV
µs
Maximum Duty Cycle
Minimum Duty Cycle
Switch Current Limit
90
%
%
5.65
A
September 5, 2013
4
Revision 1.0
Micrel, Inc.
MIC2870
Electrical Characteristics
(7)
(Continued)
V
IN
= 3.6V; L = 1μH, C
OUT
= 2.2μF, R
FRSET
= 10kΩ, R
TRSET
= 10kΩ, I
LED
= 100mA; T
A
= 25°C,
bold
values indicate
−40°C
≤ T
J
≤ 125°C,
unless otherwise noted.
Symbol
F
SW
R
ON(N)
R
ON(P)
I
LK(N)
I
LK(P)
R
DCHG
T
SD
T
SD_HYST
T
FLASH_TIMEOUT
Parameter
Oscillator Frequency
Switch On-Resistance
NMOS Switch Leakage
Current
PMOS Switch Leakage
Current
Auto-Discharge NMOS
Resistance
Overtemperature Shutdown
Threshold
Overtemperature Shutdown
Hysteresis
Flash Safety Timeout
Shutdown
Maximum timeout setting
V
VIN
= 2.7 V, I
SW
= 750 mA
V
SW
= 2.7 V, I
OUT
= 750 mA
V
EN
= 0 V, V
IN
= V
sw
= V
OUT
= 5 V
V
EN
= 0 V, V
IN
= V
OUT
= 5 V, V
sw
= 0 V
Condition
Min.
1.8
Typ.
2.0
80
80
1
1
160
160
25
1.25
5
5
Max.
2.2
Units
MHz
mΩ
µA
µA
Ω
°C
°C
s
V
EN
= 0 V, I
OUT
=
−1
mA
Current Sink Channels
Accu
LED_Ch
Match
LED_Ch
V
DROPOUT
I
LK_LED1
I
LK_LED2
V
FRSET
I
FRSET
V
TRSET
I
TRSET
Channel Current Accuracy
Channel Current Matching
Current Sink Dropout
LED1 Leakage Current
LED2 Leakage Current
FRSET Pin Voltage
FRSET Current Sourcing
TRSET Pin Voltage
TRSET Current Sourcing
V
LED1
= V
LED2
= 890mV,
I
LED1
= I
LED2
= 750mA
V
LED1
= V
LED2
= 890mV,
I
LED1
= I
LED2
= 750mA
Boost is in regulation
V
IN
= 3.6 V, V
EN
= 0 V, V
LED1
= 3.6 V
V
IN
= 3.6 V, V
EN
= 0 V, V
LED2
= 3.6 V
R
FRSET
= 10kΩ, flash mode
FRSET pin is shorted to ground,
flash mode
R
TRSET
= 10kΩ, torch mode
TRSET pin is shorted to ground, torch
mode
0.970
90
0.970
90
−10
−5
100
0.05
0.05
1.00
100
1.00
100
1.030
110
1.030
110
10
5
%
%
mV
µA
µA
V
µA
V
µA
September 5, 2013
5
Revision 1.0
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