View AAT1270_4231384.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

PRODUCT DATASHEET
AAT1270
SwitchRegTM
General Description
The AAT1270 is a high-efficiency, high-current boost converter capable of 1A maximum output current. It is an ideal power solution for LED photo flash applications in all singlecell Lithium-ion / polymer battery operated products. The AAT1270 maintains output current regulation by switching the internal high-side and low-side switch transistors. The transistor switches are pulse-width modulated at a fixed frequency of 2MHz. The high switching frequency allows the use of a small inductor and output capacitor, making the AAT1270 ideally suited for small battery-powered applications. AnalogicTech's proprietary S2CwireTM (Simple Serial ControlTM) serial digital interface is used to enable, disable and set the movie mode current level for the flash LEDs to one of 16 levels. The AAT1270 also includes a separate Flash Enable input to initiate both flash/strobe operation and the default timer, which can be used to terminate a flash event after a user-programmed delay or as a safety feature. A Flash Inhibit pin is also included which reduces flash current to movie mode level during high battery demand. The maximum flash and movie mode current is set by one external resistor; the ratio between flash and movie mode current is set at approximately 7.3:1. One or two LEDs can be connected to the AAT1270; when two LEDs are used, the output current is matched between each diode. The AAT1270 contains over-voltage protection and a thermal management system to protect the device in the event of an output open-circuit and short-circuit condition respectively. Built-in circuitry prevents excessive inrush current during start-up. The shutdown feature reduces quiescent current to less than 1.0A. The AAT1270 is available in a Pb-free, thermally-enhanced 14-pin 3x3mm STDFN package.
1A Step-Up Current Regulator for Flash LEDs
Features
* Input Voltage Range: 2.7V to 5.5V * Dual Channel Output Up to 1A Regulated Output Current (0.5A per Channel) * Up to 85% Efficiency with Small Magnetics * 2 MHz Switching Frequency * Separate Flash Enable Input * Separate Flash Inhibit Input * Single Resistor Sets Flash and Movie Mode Current Fixed Flash-to-Movie Mode Current Ratio * 16-Level Movie Mode Current via S2CwireTM * User-Programmable Safety Timer * True Load Disconnect * Input Current Limit * Over-Voltage (Open LED, Open Circuit), Short-Circuit, and Over-Temperature Protection * Shutdown Current: < 1.0A * Small Inductor Solution: 1H (0.9mm in height) * 14-pin STDFN 3x3 Package * -40 to +85C Temperature Range
Applications
* * * * * * * Camcorder Video Light (Torch Light) Cellphones / Smartphones Digital Still Cameras (DSC) LED Photo Flash Light (Strobe Light) Mobile Handsets MP3 Players PDAs and Notebook PCs
Typical Application
L1 1H Flash LEDs Lumiled LXCL-PWF1 or equivalent IN SW OUT VBATTERY CIN 2.2F
AAT1270
EN/SET FLEN FLINH RSET FLOUTA FLOUTB CT
COUT 2.2F
Movie Mode Enable and Set Flash Enable Flash Inhibit
RSET 162k
GND AGND PGND FLGND
CT 47nF
1270.2008.07.1.5
www.analogictech.com
1
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12 13 14 EP
1A Step-Up Current Regulator for Flash LEDs
Symbol
CT EN/SET FLEN AGND IN SW PGND OUT GND FLINH FLOUTB FLGND FLOUTA RSET
Function
Flash timer control input. Connect a capacitor between CT and AGND to set maximum duration for the flash pulse. A 47nF ceramic capacitor sets the flash timer to 1s. To disable the flash timer, connect CT to AGND. Enable and movie mode serial control input. EN/SET is the S2Cwire programming input to adjust the movie mode current level to one of 16 different levels based on the maximum current/7.3 set via the RSET pin. Flash enable pin. A low-to-high transition on the FLEN pin initiates a flash pulse and starts the flash timer. Analog ground pin. Connect AGND to PGND, GND, and FLGND at a single point as close to the AAT1270 as possible. Power input. Connect IN to the input power supply voltage. Connect a 2.2F or larger ceramic capacitor from IN to PGND as close as possible to the AAT1270 Boost converter switching node. Connect a 1H inductor between SW and IN. Power ground pin. Connect PGND to AGND, GND, and FLGND at a single point as close to the AAT1270 as possible. Power output of the boost converter. Connect a 2.2F or larger ceramic capacitor from OUT to PGND as close as possible to the AAT1270. Connect OUT to the anode(s) of the flash LED(s). Ground pin. Connect GND to PGND, AGND, and FLGND at a single point as close to the AAT1270 as possible. Flash inhibit pin. FLINH is an active HIGH control input with an internal 200k resistor to AGND. A low-to-high transition on the FLINH pin reduces FLOUTA and FLOUTB output currents to the maximum (default) movie-mode current level for the duration of FLINH. Strobing the FLINH pin low to high does not reset the flash timer. Flash output B. Connect cathode of Flash LEDB to FLOUT B. For a single flash LED, connect FLOUTB and FLOUTA together. For two flash LEDs, each output will conduct 50% of the total flash output current. Flash ground pin. Connect FLGND to PGND, GND, and AGND at a single point as close to the AAT1270 as possible Flash output A. Connect cathode of Flash LED A to FLOUTA. For a single flash LED, connect FLOUTA and FLOUTB together. For two flash LEDs, each output will conduct 50% of the total flash output current. Flash current setting input. A 162k resistor from RSET to AGND sets the maximum flash current available at FLOUTA or FLOUTB to 500mA. Each FLOUTA and FLOUTB channel will conduct 50% of the maximum programmed current. The AAT1270's flash-to-movie-mode ratio is fixed at 7.3. Exposed paddle (bottom); Connect EP to PGND as close as possible to the AAT1270.
Pin Configuration
STDFN33-14 (Top View)
CT EN/SET FLEN AGND IN SW PGND
1 2 3 4 5 6 7
14 13 12 11 10 9 8
RSET FLOUTA FLGND FLOUTB FLINH GND OUT
2
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Absolute Maximum Ratings1
TA = 25C unless otherwise noted. Symbol
IN, SW, OUT RSET, EN/SET, FLEN, FLINH, CT, FLOUTA, FLOUTB TJ TS TLEAD
1A Step-Up Current Regulator for Flash LEDs
Description
Maximum Rating Maximum Rating Operating Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6.0 VIN + 0.3 -40 to 150 -65 to 150 300
Units
V V C C C
Recommended Operating Conditions
Symbol
JA PD
Description
Thermal Resistance Maximum Power Dissipation
Value
50 2
Units
C/W W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
1270.2008.07.1.5
www.analogictech.com
3
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Electrical Characteristics1
VIN = 3.6V; CIN = 2.2F; COUT = 2.2F; L = 1H; RSET = 162k; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol Description Conditions Min
2.7 FLEN = IN, Set FL Load = 1A EN/SET = IN, Set FL Load = 0A, RSET = 162k EN/SET = FLEN = FLINH = GND RSET = 162k; FLOUTA + FLOUTB RSET = 162k; Movie Mode Current Set = 100%; FLOUTA + FLOUTB TA = 25C CT = 47nF 0.57 0.23 800 1000 10 137 1.5 2.0 1 140 15 2.5
1A Step-Up Current Regulator for Flash LEDs
Typ
Max
5.5 5.5 1 1 1200
Units
V V mA A mA % mA MHz s C C V V
Power Supply Input Voltage Range VIN VOUT(MAX) Maximum Output Voltage IIN(Q) ISHDN(MAX) IFL(TOTAL) IFL(MATCH) IMM(TOTAL) VIN Supply Current VIN Shutdown Current Total Output Current, Flash Mode FLOUTA and FLOUTB Current Matching Total Output Current, Movie Mode
fOSC Switching Frequency tDEFAULT Default ON time Thermal Shutdown Threshold TSD TSD(HYS) Thermal Shutdown Hysteresis EN/SET/ FLEN/ FLINH Logic Control VEN/SET(L), EN/SET, FLEN Input Low Threshold VFLEN(L) VEN/SET(H), EN/SET, FLEN Input High Threshold VFLEN(H) IEN/SET EN/SET Input Leakage Current FLEN Input Leakage Current IFLEN VT(FLINH) RIN(FLINH) tEN/SET(LOW) tEN/SET(HI_MIN) tEN/SET(HI_MAX) tEN/SET(OFF) tEN/SET(LAT) tFLEN_ON tFLEN_OFF tFLINH_ON tFLINH_OFF FLINH Input Threshold Voltage FLINH Input Resistance to AGND EN/SET Serial Interface Low Time Minimum EN/SET High Time Maximum EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout FLEN ON Delay Time FLEN OFF Delay Time FLINH ON Delay Time FLINH OFF Delay Time
0.4 1.4 VEN/SET = VIN = 5V VFLEN = VIN = 5V -1 -1 1/2 VIN 200 0.3 50 75 500 500 EN/SET = GND EN/SET = GND 100 20 100 5 75 1 1
A A V k s ns s s s s s s s
1. The AAT1270 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
4
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Typical Characteristics
Efficiency vs. Input Voltage
(Movie and Flash Mode)
90 0.12
1A Step-Up Current Regulator for Flash LEDs
Shutdown Current vs. Input Voltage
(EN/SET = FLEN = 0V) Shutdown Current (A)
5.5
85 80
68.5mA (Movie)
500mA (Flash)
0.1 0.08 0.06 0.04 0.02 0 2.7
Efficiency (%)
75 70 65 60 55 50 45 40 2.7 3.1 3.5 3.9 4.3 4.7 5.1 34.25mA (Movie) 13.7mA (Movie)
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
Switching Frequency vs. Input Voltage
(EN/SET = FLEN = 0V) Switching Frequency (MHz)
3.0 2.5 2.0 1.5 1.0 0.5 0.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Movie Mode LED Current Accuracy vs. Input Voltage
(68.5mA/Ch) LED Current Accuracy (%)
10
-40C 25C 85C
5
FLOUTB
0
-5
FLOUTA
-10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Input Voltage (V)
Movie Mode Current Matching vs. Temperature
(68.5mA/ch)
70.5 70.0
Flash Mode Current Matching vs. Temperature
(500mA/ch)
515
LED Current (mA)
69.0 68.5 68.0 67.5 67.0 66.5 66.0 65.5 -40 -15 10 35 60 85
LED Current (mA)
69.5
FLOUTA
510 505 500 495 490 485 -40
FLOUTB FLOUTA
FLOUTB
-15
10
35
60
85
Temperature (C)
Temperature (C)
1270.2008.07.1.5
www.analogictech.com
5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Typical Characteristics
Flash Mode Output Ripple
Output Voltage (top) (V) Switching Voltage (2V/div) (middle) (V) (500mA/channel; VIN = 3.1V) Inductor Current (bottom) (A)
3.26 3.22 3.18
1A Step-Up Current Regulator for Flash LEDs
Movie Mode Output Ripple
Output Voltage (top) (V) Switching Voltage (2V/div) (middle) (V) (68.5mA/channel; VIN = 3.0V) Inductor Current (bottom) (A)
3.18 3.16 3.14
0V 1.4 1.2 1.0
0V 0.2 0.0
Time (200ns/div)
Time (500ns/div)
EN/SET, FLEN Input High Threshold vs. Input Voltage
1.2 1.0
EN/SET, FLEN Input Low Threshold vs. Input Voltage
1.2 1.0
-40C VEN/SET(L) (V)
-40C
VEN/SET(H) (V)
0.8 0.6 0.4 0.2
25C 85C
0.8 0.6 0.4 0.2
85C
25C
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
EN/SET Latch Timeout vs. Input Voltage
450 400 550
EN/SET Off Timeout vs. Input Voltage
TEN/SET(OFF) (s)
TEN/SET(LAT) (s)
-40C 85C 25C
500 450 400 350 300 250 200 2.7 3.1 3.5 3.9
-40C
350 300 250 200 2.7 3.1 3.5 3.9 4.3 4.7
25C 85C
5.1
5.5
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
6
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Typical Characteristics
FLEN ON Delay Time vs. Input Voltage
200 180 160
1A Step-Up Current Regulator for Flash LEDs
Flash Inhibit On Delay Time
(EN/SET = 0V; FLEN = 3.3V; 500mA/ch) FLINH (2V/div)
TFLEN_ON (s)
140 120 100 80 60 40 20 0 2.7
-40C
0V
VOUT (2V/div) VSINK (2V/div) ILED (500mA/div)
Voltage (V)
4 2 1A 0
25C
85C
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Time (100s/div)
Movie Mode Turn On
(13.7mA/ch)
Movie Mode Turn On
(68.5mA/ch)
EN/SET (2V/div) VOUT (2V/div) VSINK (2V/div) ILED (100mA/div)
0V
EN/SET (2V/div) VOUT (2V/div) VSINK (2V/div) ILED (100mA/div)
0V 0V
0V 0V
0V
0A
0A
Time (200s/div)
Time (100s/div)
Movie Mode to Flash Mode Turn On
(68.5mA/ch to 500mA/ch) FLEN (2V/div)
0V 4 2 0 1A
Flash Mode Turn On
(500mA/ch)
FLEN (2V/div)
0V 0V
VOUT (2V/div) VSINK (2V/div) ILED (1A/div)
VOUT (2V/div) VSINK (2V/div) IIN (1A/div)
Voltage (V)
0V
0A
Time (100s/div)
Time (100s/div)
1270.2008.07.1.5
www.analogictech.com
7
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Typical Characteristics
Movie Mode Line Transient
(68.5mA/ch; VIN = 4.2V to 3.6V) 4.2V VIN (500mV/div) 3.6V ILED (AC coupled) (50mA/div) EN/SET (2V/div) VOUT (AC coupled) (100mV/div) VSINK (AC coupled) (200mV/div) ILED (100mA/div) Time (50s/div)
0A
1A Step-Up Current Regulator for Flash LEDs
Movie Mode Current Transition
(68.5mA/ch to 13.7mA/ch)
3.3V
Time (200s/div)
8
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Functional Block Diagram
IN
1A Step-Up Current Regulator for Flash LEDs
SW
OUT
FLOUTA
FLOUTB EN/SET FLEN FLINH 200k Control
RSET CT
AGND PGND FLGND GND
Functional Description
The AAT1270 is a boost converter with a current regulated output designed to drive high current white LEDs used in flash/movie light applications. The maximum flash current is set by an external resistor, RSET, which not only sets the flash current but also sets the maximum movie mode current reduced by a factor of 7.3. A flash pulse is initiated by switching the FLEN (flash enable) pin from low to high, which initiates the flash pulse and also starts the internal timer. The maximum flash time is determined by an external timing capacitor connected to the CT pin. The flash duration can be set from 50ms to a maximum of 1s. The flash timer will terminate the flash current regardless of the status of the FLEN pin.
This can be either used as a simple flash timing pulse or as a safety timer in the event of a control logic malfunction to prevent the LED from over-heating. If the safety timer is not needed in the application, it can be disabled by connecting the CT pin directly to AGND. For applications using two flash LEDs, each diode can be connected to its corresponding current sink (FLOUTA or FLOUTB) and the output current will be equally shared. In single flash LED applications, the two current sinks can be connected together to apply the full output current into the LED. If one sink pin (FLOUTA or FLOUTB) is not used, the unused current sink must be directly connected to OUT, which disables that channel.
1270.2008.07.1.5
www.analogictech.com
9
PRODUCT DATASHEET
AAT1270
SwitchRegTM
The movie-mode output current is controlled by the EN/ SET pin, which uses a single-wire S2Cwire interface to adjust the output current to one of 16 different levels. As shown in Table 1, the current settings are in logarithmic scale where each code is 1dB below the previous code. The FLEN signal takes priority over movie-mode operation. In mobile GSM systems where the phone remains in constant contact with the base station by regular communication, a FLINH pin is provided to prevent the camera flash and PA transmission pulses from occurring simultaneously, potentially causing the battery voltage to drop below the system's undervoltage lockout threshold (UVLO) or creating unwanted EMI. During a flash event, strobing the FLINH pin low-to-high will reduce the LED current to the maximum movie mode current level for the duration of FLINH. Strobing FLINH high-to-low will instruct the AAT1270 to revert the flash LED current to its default (maximum) level assuming that the FLEN pin is still active (HIGH) and that the flash timer has not expired.
1A Step-Up Current Regulator for Flash LEDs
Applications Information
LED Selection
The AAT1270 is specifically designed to drive white flash LEDs (typical forward voltage of 2.5V to 4.5V). Since the FLOUTA and FLOUTB input current sinks are matched with low voltage dependence; the LED-to-LED brightness will be matched regardless of the individual LED forward voltage (VF) levels.
Flash Mode LED Current
The LED current is controlled by the RSET resistor. For maximum accuracy, a 1% tolerance resistor is recommended. FLOUTA and FLOUTB can be programmed up to a maximum total flash current of 1A, or up to 500mA per channel. FLOUTA and FLOUTB output current is matched across the programming range. The maximum flash current in each FLOUTA and FLOUTB is set by the RSET resistor and can be calculated using the following equation:
Over-Temperature Protection
Thermal protection disables the AAT1270 when internal power dissipation becomes excessive, as it disables both MOSFETs. The junction over-temperature threshold is 140C with 15C of temperature hysteresis. The output voltage automatically recovers when the over-temperature fault condition is removed.
IFLOUTA = IFLOUTB =
81k A 81k A = = 500mA per channel RSET 162k
Movie Mode LED Current
In the default movie mode, the corresponding FLOUTA/ FLOUTB movie mode current can be calculated:
Over-Voltage Protection (Open LED, Open Circuit)
The AAT1270's output voltage is limited by internal overvoltage protection circuitry, which prevents damage to the AAT1270 from open LED or open circuit conditions. During an open circuit, the output voltage rises and reaches 5.5V (typical), and the OVP circuit disables the switching, preventing the output voltage from rising higher. Once the open circuit condition is removed, switching will resume. The controller will return to normal operation and maintain an average output voltage.
IMOVIE MODE[A/B] =
IFLOUT[A/B]MAX 7.3
For example, if an RSET value of 162k is chosen, then the FLOUTA/FLOUTB flash current is set to 500mA. For movie mode operation, the maximum current available at either FLOUTA or FLOUTB is then:
IMOVIE MODE[A/B] =
IFLOUT[A/B]MAX 500mA = = 68.5mA 7.3 7.3
10
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Alternatively, the AAT1270 S2Cwire interface programs the movie mode current at a reduced level. The FLOUTA/ FLOUTB movie-mode current can be adjusted in logarithmic fashion to one of 16 steps. Table 1 illustrates approximate movie mode levels to which the AAT1270 movie mode operation can be programmed. Percentage of Maximum Movie Mode Current (%)
100 89 79 71 63 56 50 44.7 39.8 35.5 31.6 28.2 25.1 22.4 20 0
1A Step-Up Current Regulator for Flash LEDs
faster than 1MHz, or at much slower speeds, such as 15kHz. After data is applied, EN/SET is strobed high and held high to latch the data. Once the signal applied at the EN/SET pin has been held in the logic high state for time longer than tLAT (500s), the programmed current becomes active and the internal data register is reset to zero. For subsequent current level programming, the number of rising edges corresponding to the desired code must be applied to the EN/SET pin.
S2Cwire Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Flash Timer
The AAT1270A includes a timer circuit that enables the flash current sinks for a programmed period of time. This feature eliminates the need for an external, housekeeping baseband controller to contain a safety delay routine. It also serves as a protection feature to minimize thermal issues with the flash LEDs in the event an external controller's flash software routine experiences hang-up or freeze. The flash timeout T can be calculated by the following equation:
Table 1: Programming Movie Mode Current via S2Cwire (%).
T = 21.5s/F * CT
Where T is in seconds and CT is the capacitance of the timer capacitor in F. For example, using a 47nF capacitor for CT sets the flash timeout to:
S2Cwire Serial Interface
The Simple Serial Control (S2Cwire) serial interface records rising edges at the EN/SET pin and decodes them into 16 different states. The S2Cwire serial interface has flexible timing. Data can be applied at speeds
Flash Timeout = 21.5s/F * 0.047F = 1s
THI TLO T LAT TOFF
EN/SET
1 2 n-1 n 16
Data Reg
0
n-1
0
Figure 1: S2Cwire Serial Interface Timing.
1270.2008.07.1.5
www.analogictech.com
11
PRODUCT DATASHEET
AAT1270
SwitchRegTM
The relationship between capacitance of the timer capacitor and the flash timeout is illustrated in Figure 2.
50 45 40 35 30 25 20 15 10 5 0 0 100 200 300 400 500 600 700 800 900 1000
1A Step-Up Current Regulator for Flash LEDs
inductor current rating, which is determined by the saturation characteristics. Measurements at full load and high ambient temperature should be performed to ensure that the inductor does not saturate or exhibit excessive temperature rise. The output inductor (L) is selected to avoid saturation at minimum input voltage and maximum output load conditions. Worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. At high load the switching frequency is somewhat diminished, resulting in higher IPEAK. Bench measurements are recommended to confirm actual IPEAK and to ensure that the inductor does not saturate at maximum LED current and minimum input supply voltage. The RMS current flowing through the boost inductor is equal to the DC plus AC ripple components. Under worstcase RMS conditions, the current waveform is critically continuous. The resulting RMS calculation yields worstcase inductor loss. The RMS current value should be compared against the inductor manufacturer's temperature rise, or thermal derating, guidelines:
Capacitance (nF)
Flash Timeout (ms)
Figure 2: Timer Capacitor vs. Flash Timeout.
Selecting the Boost Inductor
The AAT1270 controller utilizes PWM control and the switching frequency is fixed. To maintain 2MHz maximum switching frequency and stable operation, an 1H output inductor is recommended. Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and peak
IRMS =
IPEAK 3
Timing Diagram
FLASH FLASH FLASH FLASH FLASH FLASH TIMES OUT tDLY(CT)
MOVIE MODE
LED CURRENT (0mA)
FLASH LOWERED TO MOVIE-MODE DURING FLINH FLASH TIMES OUT SET BY CT FLASH LOWERED TO MOVIE-MODE DURING FLINH
tDLY(CT)
DATA TO MOVIE-MODE LEVEL EN/SET
FLASH ENABLE
FLASH INHIBIT
12
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Manufacturer
Murata Murata CoilCraft Cooper Bussmann Cooper Bussmann Sumida
1A Step-Up Current Regulator for Flash LEDs
Part Number
LQM2HPN1R0MG0 LQH3NPN1R0G0 LPS3010 SD3110 SD3812 CDH38D11/S
Inductance (H)
1.0 1.0 1.0 1.0 1.0 1.0
Max DC ISAT Current (A)
1.6 1.58 1.6 1.47 2.69 2.8
DCR (m)
55 110 85 68.3 48 39
Size (mm) (LxWxH)
2.5x2.0x0.9 3.0X3.0x1.0 3.0x3.0x1.0 3.1x3.1x1.0 4.0x4.0x1.2 4.0x4.0x1.2
Type
Multilayer Wirewound Wirewound Wirewound Wirewound Wirewound
Table 2: Typical Suggested Surface Mount Inductors.
For a given inductor type, smaller inductor size leads to an increase in DCR winding resistance and, in most cases, increased thermal impedance. Winding resistance degrades boost converter efficiency and increases the inductor's operating temperature:
boost regulator. MLC capacitors of type X7R or X5R are recommended to ensure good capacitance stability over the full operating temperature range. The output capacitor is selected to maintain the output load without significant voltage droop (VOUT) during the power switch ON interval. A ceramic output capacitor 2.2F is recommended (see Table 3). Typically, 6.3V or 10V rated capacitors are required for this flash LED boost output. Ceramic capacitors selected as small as 0603 are available which meet these requirements. MLC capacitors exhibit significant capacitance reduction with applied voltage. Output ripple measurements should confirm that output voltage droop and operating stability are within acceptable limits. Voltage derating can minimize this factor, but results may vary with package size and among specific manufacturers. To maintain stable operation at full load, the output capacitor should be selected to maintain VOUT between 100mV and 200mV. The boost converter input current flows during both ON and OFF switching intervals. The input ripple current is less than the output ripple and, as a result, less input capacitance is required. Voltage Rating (V)
6.3 10 6.3 10 10 10
PLOSS(INDUCTOR) = IRMS2 * DCR
Selecting the Boost Capacitors
In general, it is good design practice to place a decoupling capacitor (input capacitor) between the IN and GND pins. An input capacitor in the range of 2.2F to 10F is recommended. A larger input capacitor in this application may be required for stability, transient response, and/or ripple performance. The high output ripple inherent in the boost converter necessitates the use of low impedance output filtering. Multi-layer ceramic (MLC) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (ESR) and equivalent series inductance (ESL), and are well suited for use with the AAT1270
Manufacturer
Murata Murata Murata Murata Murata Murata
Part Number
GRM185R60J225KE26 GRM188R71A225KE15 GRM21BR70J225KA01 GRM21BR71A225KA01 GRM219R61A475KE19 GRM21BR71A106KE51
Capacitance (F)
2.2 2.2 2.2 2.2 4.7 10
Temp Co.
X5R X7R X7R X7R X5R X7R
Case Size
0603 0603 0805 0805 0805 0805
Table 3: Typical Suggested Surface Mount Capacitors.
1270.2008.07.1.5
www.analogictech.com
13
PRODUCT DATASHEET
AAT1270
SwitchRegTM
DC+ DC-
1A Step-Up Current Regulator for Flash LEDs
JP6 MCU R5 10K U2
1 2 3 4
JP7 0 C4 1F
R8 10k
EN/SET
0
SW1
2 4 1 3 5
VDD GP5 GP4 GP3
VSS GP0 GP1 GP2
8 7 6 5
FLEN
R7 330 LED2 GRN R6 330 LED1 RED
0
FLINH
SW2
0
SW3
2 4 1 3 5
2 4
1 3 5
JP3
JP4
VOUT
JP1 0 JP2 0
PIC12F675
R3 100k
R4 100k (opt) U1
D1
14 13 12 11 10 9 8
D2
JP5 EN/SET
R2 100K L1 C1 2.2F 1H C3 47nF
1 2 3 4 5 6 7
CT RSET ENSET FLA FLEN FLGND AGND FLB IN FLINH SW GND PGND OUT
AAT1270 STDFN33-14
R1 162k
C2 2.2F
L1 Murata LQM2HPN1R0MG0 1H 1.6A 55m C1, C2 Murata GRM188R71A225KE15 2.2F 0603 X7R 10V C3 Murata GRM155R71A473KA01 47nH 0402 X7R 10V
Figure 3: AAT1270 Evaluation Board Schematic.
PCB Layout Guidelines
Boost converter performance can be adversely affected by poor layout. Possible impact includes high input and output voltage ripple, poor EMI performance, and reduced operating efficiency. Every attempt should be made to optimize the layout in order to minimize parasitic PCB effects (stray resistance, capacitance, and inductance) and EMI coupling from the high frequency SW node. A suggested PCB layout for the AAT1270 1A step-up regulator is shown in Figures 4 through 7. The following PCB layout guidelines should be considered: 1. Minimize the distance from capacitor CIN and COUT's negative terminals to the PGND pins. This is especially true with output capacitor COUT, which conducts high ripple current from the output to the PGND pins.
Minimize the distance between L1 to IN and switching pin SW; minimize the size of the PCB area connected to the SW pin. 3. Maintain a ground plane and connect to the IC PGND pin(s) as well as the PGND connections of CIN and COUT. 4. Consider additional PCB exposed area for the flash LEDs to maximize heatsinking capability. This may be necessary when using high current application and long flash duration application. 5. Connect the exposed paddle (bottom of the die) to either PGND or GND. Connect AGND, FLGND to GND as close as possible to the package.
2.
14
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM 1A Step-Up Current Regulator for Flash LEDs
Figure 4: AAT1270 Evaluation Board Top Side Layout.
Figure 5: AAT1270 Evaluation Board Second Layer.
Figure 6: AAT1270 Evaluation Board Third Layer.
Figure 7: AAT1270 Evaluation Board Bottom Side Layout.
1270.2008.07.1.5
www.analogictech.com
15
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Component
U1 U2 SW1-SW3 R1 R2, R3, R4 R5, R8 R6, R7 JP1, JP2, JP7 C1, C2 C3 C4 L1 D1-D2 LED1 LED2 JP3, JP4, JP5, JP6
1A Step-Up Current Regulator for Flash LEDs
Part Number
AAT1270IFO PIC12F675 PTS645TL50 Chip Resistor Chip Resistor Chip Resistor Chip Resistor Chip Resistor GRM188R71A225KE15 GRM155R71A473KA01 GRM216R61A105KA01 LQM2HPN1R0MG0 LXCL-PWF1 CMD15-21SRC/TR8 CMD15-21VGC/TR8 PRPN401PAEN
Description
1A Step-Up Current Regulator for Flash LEDs; STDFN33-14 package 8-bit CMOS, FLASH-based C; 8-pin PDIP package Switch Tact, SPST, 5mm 162k, 1%, 1/4W; 0402 100k, 1%, 1/4W; 0603 10k, 5%, 1/4W; 0603 330, 5%, 1/4W; 0603 0, 5% 2.2F, 10V, X7R, 0603 47nF, 10V, X7R, 0402 1F, 10V, X5R, 0805 Multilayer, 1H, 1.6A, 55m White Flash LED Red LED; 1206 Green LED; 1206 Conn. Header, 2mm zip
Manufacturer
AnalogicTech Microchip ITT Industries Vishay Vishay Vishay Vishay Vishay Murata Murata Murata Murata Lumileds, Philips Chicago Miniature Lamp Chicago Miniature Lamp Sullins Electronics
Table 4: AAT1270 Evaluation Board Bill of Materials.
16
www.analogictech.com
1270.2008.07.1.5
PRODUCT DATASHEET
AAT1270
SwitchRegTM
Ordering Information
Package
STDFN33-14
1A Step-Up Current Regulator for Flash LEDs
Marking1
XXXYY
Part Number (Tape and Reel)2
AAT1270IFO-T1
All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/about/quality.aspx.
Package Information3
STDFN33-14
Detail "A" Index Area
3.000 0.050
3.000 0.050
1.700 0.050
Top View
Bottom View
0.425 0.050
0.550 0.050
0.152 REF
Side View
Pin 1 Indicator (Optional)
Detail "A"
All dimensions in millimeters.
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN, and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
1270.2008.07.1.5
www.analogictech.com
0.210 0.050
0.400 BSC
0.025 0.025
R0.2
2.570 0.050
17
PRODUCT DATASHEET
AAT1270
SwitchRegTM 1A Step-Up Current Regulator for Flash LEDs
Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611
(c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech's terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
18
www.analogictech.com
1270.2008.07.1.5

▲Up To Search▲

Price & Availability of AAT1270

	To Download AAT1270 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .