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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
General Description
The AAT1239-1 is a high frequency, high efficiency constant current boost converter capable of driving up to ten (10) series-connected white LEDs or 40V. It is an ideal power solutions for backlight applications with up to ten white LEDs in series. The input voltage is 2.7V to 5.5V for single-cell lithium-ion/polymer (Li-ion) based portable devices. The LED current is digitally controlled across a 6x operating range using AnalogicTech's Simple Serial ControlTM (S2CwireTM) interface. Programmability across 26 discrete current steps provides high resolution, low noise, flicker-free, constant LED outputs. In programming AAT1239 operation, LED brightness increases based on the data applied at the EN/SET pin. The SEL logic pin changes the feedback voltage between two programmable ranges. The AAT1239-1 features a high current limit and fast, stable transitions for stepped or pulsed current applications. The high switching frequency (up to 2MHz) provides fast response and allows the use of ultra-small external components, including chip inductors and capacitors. Fully integrated control circuitry simplifies design and reduces total solution size. The AAT1239-1 offers a true load disconnect feature which isolates the load from the power source while in the OFF or disabled state. This eliminates leakage current, making the devices ideally suited for battery-powered applications. The AAT1239-1 is available in the Pb-free, thermallyenhanced 12-pin TSOPJW package.
40V Step-Up Converter for 4 to 10 White LEDs
Features
* Input Voltage Range: 2.7V to 5.5V * Maximum Continuous Output 40V @ 30mA * Drives up to 10 LEDs in Series Constant LED Current with 3.5% Accuracy Over Temperature and Input Voltage Range * Digital Control with S2Cwire Single Wire Interface 26 Discrete Steps No PWM Control Required No Additional Circuitry * Up to 85% Efficiency * Up to 2MHz Switching Frequency Allows Small External Chip Inductor and Capacitors * Hysteretic Control No External Compensation Components Excellent Load Transient Response High Efficiency at Light Loads * Integrated Soft Start with No External Capacitor * True Load Disconnect Guarantees <1.0A Shutdown Current * Selectable Feedback Voltage Ranges for High Resolution Control of Load Current * Short-Circuit, Over-Voltage, and Over-Temperature Protection * 12-Pin TSOPJW Package * -40C to +85C Temperature Range
Applications
* * * * * Color Display Backlight Digital Still Cameras (DSCs) Digital Photo Frames PDAs and Notebook PCs White LED Drivers
Typical Application
L1 2.2H DS1 SS16L or equivalent
PVIN Li-Ion: VIN = 2.7V to 4.2V
C1 2.2F
LIN SW
C2 2.2F M673 R2 374k
VIN
AAT1239-1 OVP
Enable/Set Feedback Voltage Select
EN/SET SEL FB PGND AGND
ILED 20mA
R3 12k
R1 (RBALLAST) 30.1
White LEDs OSRAM LW M678 or equivalent
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Pin Descriptions
Pin #
1 2 3 4 5 6, 7 8 9 10 11 12
40V Step-Up Converter for 4 to 10 White LEDs
Symbol
PVIN EN/SET SEL VIN N/C SW PGND AGND FB OVP LIN
Function
Input power pin; connected to the source of the P-channel MOSFET. Connect to the input capacitor(s). IC enable pin and S2Cwire input control to set output current. FB voltage range select. A logic LOW sets the FB voltage range from 0.4V to 0.1V; a logic HIGH sets the FB voltage range from 0.6V to 0.3V. Input voltage for the converter. Connect directly to the PVIN pin. No connection. Boost converter switching node. Connect the power inductor between this pin and LIN. Power ground for the boost converter. Ground pin. Feedback pin. Connect a resistor to ground to set the maximum LED current. Feedback pin for over-voltage protection sense. Switched power input. Connect the power inductor between this pin and SW.
Pin Configuration
TSOPJW-12 (Top View)
PVIN EN/SET SEL VIN N/C SW
1 2 3 4 5 6
12 11 10 9 8 7
LIN OVP FB AGND PGND SW
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1239-1.2008.10.1.2
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Part Number Descriptions
Part Number
AAT1239ITP-1 SEL Polarity HIGH 0.6V VFB 0.3V LOW 0.4V VFB 0.1V
40V Step-Up Converter for 4 to 10 White LEDs
S2C Feedback Voltage Programming
See Table 2
Absolute Maximum Ratings1
TA = 25C unless otherwise noted. Symbol
PVIN, VIN SW LIN, EN/SET, SEL, FB TJ TS TLEAD
Description
Input Voltage Switching Node Maximum Rating Operating Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6.0 45 VIN + 0.3 -40 to 150 -65 to 150 300
Units
V V V C C C
Thermal Information
Symbol
JA PD
Description
Thermal Resistance Maximum Power Dissipation
Value
160 625
Units
C/W mW
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.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Electrical Characteristics1
TA = -40C to +85C unless otherwise noted. Typical values are at 25C, VIN = 3.6V. Symbol
Power Supply PVIN, VIN VOUT(MAX) IQ ISHDN IOUT VLINEREG(FB)/VIN RDS(ON) L RDS(ON) IN TSS VOVP ILIMIT TSD THYS SEL, EN/SET VSEL(L) VSEL(H) VEN/SET(L) VEN/SET(H) TEN/SET (LO) TEN/SET(HI) TOFF TLAT IEN/SET AAT1239-1 VFB FB Pin Regulation VIN = 2.7V to 5.5V, SEL = GND, EN/SET = DATA16 VIN = 2.7V to 5.5V, SEL = HIGH, EN/SET = HIGH 0.085 0.54 0.1 0.6 1.115 V 0.66
40V Step-Up Converter for 4 to 10 White LEDs
Description
Input Voltage Range Maximum Output Voltage Operating Current Shutdown Current Maximum Continuous Output Current2 Line Regulation Low Side Switch On Resistance Input Disconnect Switch On Resistance Soft-Start Time Over-Voltage Protection Threshold Over-Voltage Hysteresis N-Channel Current Limit TJ Thermal Shutdown Threshold TJ Thermal Shutdown Hysteresis SEL Threshold Low SEL Threshold High Enable Threshold Low Enable Threshold High EN/SET Low Time EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout EN/SET Input Leakage
Conditions
Min
2.7
Typ
Max
5.5 40 70 1.0 30
Units
V V A A mA % m m s
SEL = GND, FB = 0.1V EN/SET = GND 2.7V < VIN < 5.5V, VOUT = 40V VIN = 2.7V to 5.5V, VFB = 0.6V 0.7 135 180 From Enable to Output Regulation; VFB = 300mV VOUT Rising VOUT Falling 400 1.1 1.2 100 2.5 140 15
1.3
V mV A C C V V V V s s s s A
0.4 1.4 0.4 VEN/SET VEN/SET VEN/SET VEN/SET VEN/SET < > < > = 0.6V 1.4V 0.6V 1.4V 5V VIN = 5V 1.4 0.3 75 75 500 500 1
-1
1. Specification over the -40C to +85C operating temperature range is assured by design, characterization, and correlation with statistical process controls. 2. Maximum continuous output current increases with reduced output voltage, but may vary depending on operating efficiency and thermal limitations.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Typical Characteristics
(10 White LEDs; RBALLAST = 30.1)
80 78 78 76
40V Step-Up Converter for 4 to 10 White LEDs
Efficiency vs. LED Current
Efficiency vs. LED Current
(9 White LEDs; RBALLAST = 30.1) VIN = 5V
Efficiency (%)
76 74 72 70 68 66 2
Efficiency (%)
VIN = 5V
74 72 70 68 66
VIN = 4.2V
VIN = 3.6V
VIN = 4.2V
4 6 8
VIN = 3.6V
10 12 14 16 18 20
2
4
6
8
10
12
14
16
18
20
ILED (mA)
ILED (mA)
Shutdown Current vs. Input Voltage
(EN = GND) Input Voltage (top) (V) Output Voltage (middle) (V)
1.0
(10 White LEDs; RBALLAST = 30.1) Feedback Voltage (bottom) (V)
4.2V 3.6V 33.2 33 32.8 0.62 0.6 0.58
Line Transient
Shutdown Current (A)
0.8 0.6 0.4 0.2 0.0 2.7 3.1 3.5 3.9 4.3 4.7
25C 85C
-40C
5.1 5.5
Input Voltage (V)
Time (50s/div)
Accuracy ILED vs. Input Voltage
(VFB = 0.6V; RBALLAST = 30.1)
2.0 1.5 1.5
Accuracy ILED vs. Temperature
(VFB = 0.6V; RBALLAST = 30.1)
Accuracy ILED (%)
1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 2.7 3.2 3.7 4.2 4.7
Accuracy ILED (%)
-40C
1.0 0.5 0.0 -0.5 -1.0 -1.5 -40
25C
85C
5.2
5.7
-15
10
35
60
85
Input Voltage (V)
Temperature (C)
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Typical Characteristics
Soft Start
(10 White LEDs; VFB = 0.6V) Feedback Voltage (middle) (V) Feedback Voltage (middle) (V) EnableVoltage (top) (V) Inductor Current (bottom) (A)
0.6 0.4 0.2 0 2 1 0 0V 3.3V
40V Step-Up Converter for 4 to 10 White LEDs
Soft Start
(10 White LEDs; VFB = 0.3V) EnableVoltage (top) (V) Inductor Current (bottom) (A)
3.3V 0V 0.4 0.2 0 2 1 0 0V
Time (200s/div)
Time (200s/div)
Shutdown
(10 White LEDs; VFB = 0.6V) EnableVoltage (top) (V) Feedback Voltage (middle) (V) EnableVoltage (top) (V) Feedback Voltage (middle) (V) Inductor Current (bottom) (A)
3.3V 0V 0.6 0.4 0.2 0 0.5 0.0 3.3V 0V 0.4 0.2 0
Shutdown
(10 LEDs; VFB = 0.3V) Inductor Current (bottom) (A)
0.5 0
Time (100s/div)
Time (50s/div)
Output Ripple
(10 White LEDs; VIN = 3.6V; COUT = 2.2F; ILED = 13mA) VOUT (AC Coupled) (20mV/div) VSW (20V/div) IL (500mA/div) VOUT (AC Coupled) (20mV/div) VSW (20V/div) IL (500mA/div)
Output Ripple
(10 White LEDs; VIN = 3.6V; COUT = 2.2F; ILED = 20mA)
Time (200ns/div)
Time (200ns/div)
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Typical Characteristics
Transition of LED Current
(10 White LEDs; SEL = Low; ILED = 3mA to 13mA) Output Voltage (top) (V) Output Voltage (top) (V)
34
40V Step-Up Converter for 4 to 10 White LEDs
Transition of LED Current
(10 White LEDs; SEL = Low; ILED = 13mA to 6mA)
34
Feedback Voltage (bottom) (V)
Feedback Voltage (bottom) (V)
32 30 28 0.4 0.3 0.2 0.1 0.0
32 30 0.4 0.3 0.2 0.1 0.0
Time (50s/div)
Time (50s/div)
Input Disconnect Switch Resistance vs. Input Voltage
300 280 260 240
Low Side Switch On Resistance vs. Input Voltage
120C 100C
RDS(ON)IN (m)
240 220 200 180 160 140 2.7 3.1 3.5 3.9
100C
RDS(ON)L (m)
260
120C
220 200 180 160 140 120 100 4.3 4.7 5.1 5.5 80 2.7
25C
85C
85C 25C
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
EN/SET Latch Timeout (s)
350 300
EN/SET Off Timeout vs. Input Voltage
EN/SET Off Timeout (s)
300 250 200
250 200 150 100 50 2.7
-40C
-40C 85C 25C
25C
85C
150 100 2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Typical Characteristics
Enable High Threshold (VIH) vs. Input Voltage
Enable High Threshold (VIH) (V)
1.2 1.1 1.0 0.9 0.8 0.7 0.6 2.7
40V Step-Up Converter for 4 to 10 White LEDs
Enable Low Threshold (VIL) vs. Input Voltage
Enable Low Threshold (VIL) (V)
1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
25C -40C 85C
-40C 25C 85C
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Functional Block Diagram
40V Step-Up Converter for 4 to 10 White LEDs
PVIN
LIN
VIN
OVP
EN/SET
SW
Control
FB Reference Output Select
SEL
AGND
PGND
Functional Description
The AAT1239-1 consists of a DC/DC boost controller, an integrated slew rate controlled input disconnect MOSFET switch, and a high voltage MOSFET power switch. A high voltage rectifier, power inductor, output capacitor, and sense resistors are required to implement a DC/DC constant current boost converter. The input disconnect switch is activated when a valid input voltage is present and the EN/SET pin is pulled high. The slew rate control on the P-channel MOSFET ensures minimal inrush current as the output voltage is charged to the input voltage, prior to the switching of the N-channel power MOSFET. Monotonic turn-on is guaranteed by the integrated soft-start circuitry. Soft-start eliminates output voltage overshoot across the full input voltage range and all loading conditions. The maximum current through the LED string is set by the ballast resistor and the feedback voltage of the IC. The output current may be programmed by adjusting the level of the feedback reference voltage which is programmed through the S2Cwire interface. The SEL pin selects one of two feedback voltage ranges. In the AAT1239-1, the SEL function is inverted in that the FB pin voltage can be programmed from 0.4V to 0.1V with
a logic LOW applied to the SEL pin and 0.6V to 0.3V with a logic HIGH applied to the SEL pin. The feedback voltage can be set to any one of 16 current levels within each FB range, providing high-resolution control of the LED current, using the single-wire S2Cwire control. For some applications requiring a short duration of boosting current applying a low-to-high transition on the AAT1239-1's SEL pin, LED current can be programmed up to 3x. The step size is determined by the programmed voltage at the FB pin where the internal default setting is 1.5x in the AAT1239-1.
Control Loop
The AAT1239-1 provides the benefits of current mode control with a simple hysteretic output current loop providing exceptional stability and fast response with minimal design effort. The device maintains exceptional constant current regulation, transient response, and cycle-by-cycle current limit without additional compensation components. The AAT1239-1 modulates the power MOSFET switching current to maintain the programmed FB voltage. This allows the FB voltage loop to directly program the
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
N-channel power MOSFET. Monotonic turn-on is guaranteed by the built-in soft-start circuitry. Soft start eliminates output current overshoot across the full input voltage range and all loading conditions. After the soft start sequence has terminated, the initial LED current is determined by the internal, default FB voltage across the external ballast resistor at the FB pin. Additionally, the AAT1239-1 has been designed to offer the system designer two choices for the default FB voltage based on the state of the SEL pin. Changing the LED current from its initial default setting is easy by using the S2Cwire single wire serial interface; the FB voltage can be decreased (as in the AAT1239-1; see Table 2) relative to the default FB voltage. required inductor current in order to maintain the desired LED current. The switching cycle initiates when the N-channel MOSFET is turned ON and current ramps up in the inductor. The ON interval is terminated when the inductor current reaches the programmed peak current level. During the OFF interval, the input current decays until the lower threshold, or zero inductor current, is reached. The lower current is equal to the peak current minus a preset hysteresis threshold, which determines the inductor ripple current. The peak current is adjusted by the controller until the LED output current requirement is met. The magnitude of the feedback error signal determines the average input current. Therefore, the AAT1239-1 controller implements a programmed current source connected to the output capacitor, parallel with the LED string and ballast resistor. There is no right-half plane zero, and loop stability is achieved with no additional compensation components. An increase in the feedback voltage (VFB) results in an increased error signal sensed across the ballast resistor (R1). The controller responds by increasing the peak inductor current, resulting in higher average current in the inductor and LED string(s). Alternatively, when the VFB is reduced, the controller responds by decreasing the peak inductor current, resulting in lower average current in the inductor and LED string(s). Under light load conditions, the inductor OFF interval current goes below zero and the boost converter enters discontinuous mode operation. Further reduction in the load current results in a corresponding reduction in the switching frequency. The AAT1239-1 provides pulsed frequency operation which reduces switching losses and maintains high efficiency under light load conditions. Operating frequency varies with changes in the input voltage, output voltage, and inductor size. Once the boost converter has reached continuous mode, further increases in the LED current will not significantly change the operating frequency. A small 2.2H (20%) inductor is selected to maintain high frequency switching (up to 2MHz) and high efficiency operation for outputs up to 40V.
Current Limit and Over-Temperature Protection
The switching of the N-channel MOSFET terminates when a current limit of 2.5A (typical) is exceeded. This minimizes power dissipation and component stresses under overload and short-circuit conditions. Switching resumes when the current decays below the current limit. Thermal protection disables the AAT1239-1 when internal dissipation becomes excessive. Thermal protection 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.
Over-Voltage Protection
Over-voltage protection prevents damage to the AAT1239-1 during open-circuit or high output voltage conditions. An over-voltage event is defined as a condition where the voltage on the OVP pin exceeds the overvoltage threshold limit (VOVP = 1.2V typical). When the voltage on the OVP pin has reached the threshold limit, the converter stops switching and the output voltage decays. Switching resumes when the voltage on the OVP pin drops below the lower hysteresis limit, maintaining an average output voltage between the upper and lower OVP thresholds multiplied by the resistor divider scaling factor.
Soft Start / Enable
The input disconnect switch is activated when a valid input voltage is present and the EN/SET pin is pulled high. The slew rate control on the P-channel MOSFET ensures minimal inrush current as the output voltage is charged to the input voltage, prior to switching of the
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to soft start.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Application Information
Over-Voltage Protection
OVP Protection with Open Circuit Failure
The OVP protection circuit consists of a resistor network tied from the output voltage to the OVP pin (see Figure 1). To protect the device from open circuit failure, the resistor divider can be selected such that the over-voltage threshold occurs prior to the output reaching 40V (VOUT(MAX)). The value of R3 should be selected from 10k to 20k to minimize losses without degrading noise immunity.
40V Step-Up Converter for 4 to 10 White LEDs
Assume R3 = 12k and VOUT(MAX) = 40V. Selecting 1% resistor for high accuracy, this results in R2 = 374k (rounded to the nearest standard value). The minimum OVP threshold can be calculated:
VOUT(OVP_MIN) = VOVP(MIN) * = 35.4V
R2 +1 R3
To avoid OVP detection and subsequent reduction in the programmed output current (see following section), the maximum operating voltage should not exceed the minimum OVP set point.
R2 = R3 *
VOUT(MAX) -1 VOVP
VOUT(MAX) < VOUT(OVP_MIN)
In some cases, this may disallow configurations with high LED forward voltage (VFLED) and/or greater than ten series white LEDs. VFLED unit-to-unit tolerance can be as high as +15% of nominal for white LED devices.
VOUT AAT1239-1 R2 OVP GND R3 COUT
OVP Constant Voltage Operation
Under closed loop constant current conditions, the output voltage is determined by the operating current, LED forward voltage characteristics (VFLED), quantity of series connected LEDs (N), and the feedback pin voltage (VFB).
VOUT = VFB + N * VFLED
Figure 1: Over-Voltage Protection Circuit.
Over Voltage Protection Pin (top) (V) Inductor Current (bottom)(A)
1.238V 1.142V 40 30 4 2 0
When the rising OVP threshold is exceeded, switching is stopped and the output voltage decays. Switching automatically restarts when the output drops below the lower OVP hysteresis voltage (100mV typical) and, as a result, the output voltage increases. The cycle repeats, maintaining an average DC output voltage proportional to the average of the rising and falling OVP levels (multiplied by the resistor divider scaling factor). High operating frequency and small output voltage ripple ensure DC current and negligible flicker in the LED string(s). The waveform in Figure 3 shows the output voltage and LED current at cold temperature with a ten series white LED string and VOVP = 40V. As shown, the output voltage rises as a result of the increased VFLED which triggers the OVP constant voltage operation. Self heating of the LEDs triggers a smooth transition back to constant current control.
Output Voltage (middle) (V)
Time (4ms/div)
Figure 2: Over-Voltage Protection Open Circuit Response (No LED).
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Over-Voltage Protection Cold Temperature Apply Self-Recovery
40V Step-Up Converter for 4 to 10 White LEDs
where: VFB(MAX) = 0.4V when SEL = Low VFB(MAX) = 0.6V when SEL = High i.e., for a maximum LED current of 20mA (SEL = High):
VOUT (5V/div) ILED (200mA/div)
RBALLAST =
Figure 3: Over-Voltage Protection Constant Voltage Operation (10 White LEDs; ILED = 20mA; R2 = 12k; R3 = 374k). While OVP is active, the maximum LED current programming error (ILED) is proportional to voltage error across an individual LED (VFLED).
VFB 0.6 = = 30 30.1 ILED(MAX) 0.020
RBALLAST ()
Maximum ILED Current (mA)
30 25 20 15 10 5
SEL = High 20.0 24.3 30.1 40.2 60.4 121.0
SEL = Low 13.3 16.2 20.0 26.7 40.2 80.6
(N * VFLED(TYP) - VOUT(OVP_MIN) - VFB) VFLED = N
To minimize the ILED error, the minimum OVP voltage (VOUT(OVP_MIN)) may be increased, yielding a corresponding increase in the maximum OVP voltage (VOUT(OVP_MAX)). Measurements should confirm that the maximum switching node voltage (VSW(MAX)) is less than 45V under worstcase operating conditions.
Table 1: Maximum LED Current and RBALLAST Resistor Values (1% Resistor Tolerance). Typical white LEDs are driven at maximum continuous currents of 15mA to 20mA. The maximum number of series connected LEDs is determined by the minimum OVP voltage of the boost converter (VOUT(OVP_MIN)), minus the maximum feedback voltage (VFB(MAX)) divided by the maximum LED forward voltage (VFLED(MAX)). VFLED(MAX) can be estimated from the manufacturers' datasheet at the maximum LED operating current.
VSW(MAX) = VOVP(MAX) *
R3 + 1 + VF + VRING R2
VOUT(OVP_MIN) = VOVP(TYP) *
R2 +1 R3
VF = -Schottky Diode DS1 forward voltage at turn-OFF VRING = Voltage ring occurring at turn-OFF
N=
(VOUT(OVP_MIN) - VFB(MAX)) VFLED(MAX)
LED Selection and Current Setting
The AAT1239-1 is well suited for driving white LEDs with constant current. Applications include main and sub-LCD display backlighting, and color LEDs. The LED current is controlled by the FB voltage and the ballast resistor. For maximum accuracy, a 1% tolerance resistor is recommended. The ballast resistor (RBALLAST) value can be calculated as follows:
Figure 4 shows the schematic of using ten LEDs in series. Assume VFLED @ 20mA = 3.5V (typical) from LW M673 (OSRAM) datasheet.
VOUT(OVP_MIN) = 1.2V *
374k + 1 = 38.6V 10.4k
N=
38.6V - 0.6V 3.5V
10.9
Therefore, under these typical operating conditions, ten LEDs can be used in series.
RBALLAST =
VFB(MAX) ILED(MAX)
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1239-1.2008.10.1.2
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
DS1 L1 2.2H D1 LED D6 LED JP1
1 2 3
VCC
R4 10K
U1
1 2 3 4 5 6
C1 2.2F
Enable JP2
1 2 3
VIN EN SEL VP N/C SW
LIN OVP FB GND PGND SW
12 11 10 9 8 7
R2 374K R3 12K
D2 LED D3 LED D4 LED D5 LED C2 2.2F
D7 LED D8 LED D9 LED D10 LED
AAT1239-1 TSOP12JW R1 30.1
Select
C1 10V 0603 X5R 2.2F GRM188R60J225KE01D C2 50V 1206 X7R 2.2F GRM31CR71H225KA88 L1 2.2H SD3814-2R2 or SD3110-2R2 DS1 SS16L D1-D10 LW M673 White LED
other alternatives: more stability at 40V: C2 50V 1206 X7R 4.7F GRM31CR71H475K under 20V application: C2 25V 0805 X7R 2.2F GRM21BR71E225KA73L
Figure 4: AAT1239-1 White LED Boost Converter Schematic.
LED Brightness Control
The AAT1239-1 uses S2Cwire programming to control LED brightness and does not require PWM (pulse width modulation) or additional control circuitry. This feature greatly reduces the burden on a microcontroller or system IC to manage LED or display brightness, allowing the user to "set it and forget it." With its high-speed serial interface (1MHz data rate), the output current of the AAT1239-1 can be changed successively to brighten or dim the LEDs in smooth transitions (i.e., to fade out) or in abrupt steps, giving the user complete programmability and real-time control of LED brightness.
LED Current (mA)
25 20 15 10
Default
SEL=HIGH
SEL=LOW
5 0
1
4
7
10
13
16
S2Cwire Data Register
Figure 5: Programming AAT1239-1 LED Current with RBALLAST = 30.1.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
rising edges of the EN/SET input and decodes them into 16 individual states. Each state corresponds to a reference feedback voltage setting on the FB pin, as shown in Table 2. Alternatively, toggling the SEL logic pin from low to high implements stepped or pulsed LED currents by increasing the FB pin voltage. Figure 6 illustrates the SELECT pin scaling factor, defined as the LED current with SEL=HIGH divided by the LED current with SEL=LOW. In the AAT1239-1, the possible scaling factors are 3.0x to 1.5x with the internal default setting of 1.5x.
3. 5
S2Cwire Serial Interface Timing
The S2Cwire single wire serial interface data can be clocked-in at speeds up to 1MHz. After data has been submitted, EN/SET is held high to latch the data for a period TLAT. The FB pin voltage is subsequently changed to the level as defined by the state of the SEL logic pin. When EN/SET is set low for a time greater than TOFF, the AAT1239-1 is disabled. When the AAT1239-1 is disabled, the register is reset to its default value. In the AAT1239-1, the FB pin voltage is set to 0.3V if the EN/SET pin is subsequently pulled HIGH.
Select Pin Scaling Factor (Low to High)
3. 0 2. 5 2. 0 (Default) 1. 5 1. 0 1 4 7 10 13 16
S2Cwire Data Register
S2Cwire Feedback Voltage Programming
The FB pin voltage is set to the default level at initial powerup. The AAT1239-1 is programmed through the S2Cwire interface. Table 2 illustrates FB pin voltage programming for the AAT1239-1. The rising clock edges applied at the EN/SET pin determine the FB pin voltage. If a logic LOW is applied at the SEL pin of the AAT1239-1, the default feedback voltage range becomes 0.4V to 0.1V and 0.6V to 0.3V for a logic HIGH condition at the SEL pin.
Figure 6: AAT1239-1 SEL Pin Scaling Factor: ILED (SEL = High) Divided by ILED (SEL = Low).
S2Cwire Serial Interface
AnalogicTech's S2Cwire single wire serial interface is a proprietary high-speed single-wire interface available only from AnalogicTech. The S2Cwire interface records
THI TLO T LAT TOFF
EN/SET
1 2 n-1 n 16
Data Reg
0
n-1
0
Figure 7: AAT1239-1 S2Cwire Timing Diagram to Program the Output Voltage.
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1239-1.2008.10.1.2
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Rising Clock Edges/Data Register
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
40V Step-Up Converter for 4 to 10 White LEDs
SEL = Low Reference Voltage (V)
0.4 (default) 0.38 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.20 0.18 0.16 0.14 0.12 0.10
SEL = High Reference Voltage (V)
0.6 (default) 0.58 0.56 0.54 0.52 0.50 0.48 0.46 0.44 0.42 0.40 0.38 0.36 0.34 0.32 0.30
LED Current (mA); RBALLAST = 30.1
13.29 12.62 11.96 11.30 10.63 9.97 9.30 8.64 7.97 7.31 6.64 5.98 5.32 4.65 3.99 3.32
LED Current (mA); RBALLAST = 30.1
19.93 19.27 18.60 17.94 17.28 16.61 15.95 15.28 14.62 13.95 13.29 12.62 11.96 11.30 10.63 9.97
Table 2: AAT1239-1 S2Cwire Reference Feedback Voltage Control Settings With RBALLAST = 30.1 (Assumes Nominal Values)*.
Selecting the Schottky Diode
To ensure minimum forward voltage drop and no recovery, high voltage Schottky diodes are considered the best choice for the AAT1239-1 boost converter. The output diode is sized to maintain acceptable efficiency and reasonable operating junction temperature under full load operating conditions. Forward voltage (VF) and package thermal resistance (JA) are the dominant factors to consider in selecting a diode. The diode non-repetitive peak forward surge current rating (IFSM) should be considered for high pulsed load applications, such as camera flash. IFSM rating drops with increasing conduction period. Manufacturers' datasheets should be consulted to verify reliability under peak loading conditions. The diode's published current rating may not reflect actual operating conditions and should be used only as a comparative measure between similarly rated devices. 40V rated Schottky diodes are recommended for outputs less than 30V, while 60V rated Schottky diodes are recommended for outputs greater than 35V.
The switching period is divided between ON and OFF time intervals.
1 = TON + TOFF FS
During the ON time, the N-channel power MOSFET is conducting and storing energy in the boost inductor. During the OFF time, the N-channel power MOSFET is not conducting. Stored energy is transferred from the input battery and boost inductor to the output load through the output diode. Duty cycle is defined as the ON time divided by the total switching interval.
D=
TON TON + TOFF
= TON FS
*All table entries are preliminary and subject to change without notice.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
high efficiency under light load. The rectifier reverse current increases dramatically at elevated temperatures. The maximum duty cycle can be estimated from the relationship for a continuous mode boost converter. Maximum duty cycle (DMAX) is the duty cycle at minimum input voltage (VIN(MIN)).
Selecting the Boost Inductor
The AAT1239-1 controller utilizes hysteretic control and the switching frequency varies with output load and input voltage. The value of the inductor determines the maximum switching frequency of the boost converter. Increased output inductance decreases the switching frequency and switching loss, but results in higher peak currents and increased output voltage ripple. To maintain 2MHz maximum switching frequency and stable operation, an output inductor sized from 1.5H to 2.7H is recommended. For higher efficiency in Li-ion battery applications (VIN from 3.0V to 4.2V) and stable operation, increasing the inductor size up to 10H is recommended. Figure 15 and 16 show the special enhanced efficiency application. A better estimate of DMAX is possible once VF is known.
V - VIN(MIN) DMAX = OUT VOUT
The average diode current is equal to the output current.
IAVG(TOT) = IOUT
The average output current multiplied by the forward diode voltage determines the loss of the output diode.
PLOSS(DIODE) = IAVG(TOT) * VF = IOUT * VF
For continuous LED currents, the diode junction temperature can be estimated.
DMAX =
(VOUT + VF - VIN(MIN)) (VOUT + VF)
TJ(DIODE) = TAMB + JA * PLOSS(DIODE)
Output diode junction temperature should be maintained below 110C, but may vary depending on application and/or system guidelines. The diode JA can be minimized with additional PCB area on the cathode. PCB heat-sinking the anode may degrade EMI performance. The reverse leakage current of the rectifier must be considered to maintain low quiescent (input) current and
Where VF is the Schottky diode forward voltage. If not known, it can be estimated at 0.5V. Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and peak inductor current rating, which is determined by the saturation characteristics. Measurements at full load and high ambient temperature should be completed to ensure that the inductor does not saturate or exhibit excessive temperature rise.
Manufacturer
Taiwan Semiconductor Co., Ltd. Diodes, Inc Zetex
Part Number
SS16L SS15L SS14L B340LA ZHCS350
Rated Forward Current (A)
1.1 3 0.35
Non-Repetitive Peak Surge Current (A)
30 30 30 70.0 4.2
Rated Voltage (V)
60 50 40 40 40
Thermal Resistance (JA, C/W)
45 45 45 25 330
Size (mm) (LxWxH)
3.8x1.9x1.43 3.8x1.9x1.43 3.8x1.9x1.43 5.59x2.92x2.30 1.7x0.9x0.8
Case
Sub SMA Sub SMA Sub SMA SMA SOD523
Table 3: Typical Surface Mount Schottky Rectifiers for Various Output Levels.
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1239-1.2008.10.1.2
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
be compared against the manufacturer's temperature rise, or thermal derating, guidelines. The output inductor (L) is selected to avoid saturation at minimum input voltage, maximum output load conditions. Peak current may be estimated using the following equation, assuming continuous conduction mode. Worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. Switching frequency (FS) can be estimated from the curves and assumes a 2.2H inductor.
IRMS =
IPEAK
3
IPEAK =
IOUT D * VIN(MIN) + MAX (1 - DMAX) (2 * FS * L)
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.
At light load and low output voltage, the controller reduces the operating frequency to maintain maximum operating efficiency. As a result, further reduction in output load does not reduce the peak current. Minimum peak current can be estimated from 0.5A to 0.75A. At high load and high output voltages, the switching frequency is somewhat diminished, resulting in higher IPEAK. Bench measurements are recommended to confirm actual IPEAK and ensure that the inductor does not saturate at maximum LED current and minimum input voltage. The RMS current flowing through the boost inductor is equal to the DC plus AC ripple components. Under worst-case RMS conditions, the current waveform is critically continuous. The resulting RMS calculation yields worst-case inductor loss. The RMS current value should
PLOSS(INDUCTOR) = IRMS2 * DCR
To ensure high reliability, the inductor case temperature should not exceed 100C. In some cases, PCB heatsinking applied to the LIN node (non-switching) can improve the inductor's thermal capability. PCB heatsinking may degrade EMI performance when applied to the SW node (switching) of the AAT1239-1. Shielded inductors provide decreased EMI and may be required in noise sensitive applications. Unshielded chip inductors provide significant space savings at a reduced cost compared to shielded (wound and gapped) inductors. In general, chip-type inductors have increased winding resistance (DCR) when compared to shielded, wound varieties.
Manufacturer
Sumida www.sumida.com
Part Number
CDRH2D14-2R2 CDRH2D14-4R7 CDRH4D22/HP-4R7 CDRH3D18-100NC SD3814-2R2 SD3110-2R2 SD3118-4R7 SD3118-100 NP03SB-2R0M NR3010T-2R2M NP03SB4R7 NP03SB100M
Inductance (H)
2.2 4.7 4.7 10 2.2 2.2 4.7 10 2 2.2 4.7 10
Maximum DC ISAT Current (mA)
1500 1000 2200 900 1900 910 1020 900 1900 1100 1200 800
DCR (m)
75 135 66 164 77 161 162 295 32 95 47 100
Size (mm) LxWxH
3.2x3.2x1.55 3.2x3.2x1.55 5.0x5.0x2.4 4.0x4.0x2.0 4.0x4.0x1.0 3.1x3.1x1.0 3.1x3.1x1.8 3.1x3.1x1.8 4.0x4.0x1.8 3.0x3.0x1.0 4.0x4.0x1.8 4.0x4.0x1.8
Type
Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded Shielded
Cooper Electronics www.cooperet.com
Taiyo Yuden www.t-yuden.com
Table 4: Recommended Inductors for Various Output Levels (Select IPEAK < ISAT).
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17
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Inductor Efficiency Considerations
The efficiency for different inductors is shown in Figure 8 for ten white LEDs in series. Smaller inductors yield increased DCR and reduced operating efficiency.
75 CDRH5D16F-2R2 (29m)
40V Step-Up Converter for 4 to 10 White LEDs
recommended to ensure good capacitance stability over the full operating temperature range. The output capacitor is sized to maintain the output load without significant voltage droop (VOUT) during the power switch ON interval, when the output diode is not conducting. A ceramic output capacitor from 2.2F to 4.7F is recommended (see Table 5). Typically, 50V rated capacitors are required for the 40V maximum boost output. Ceramic capacitors sized as small as 0805 or 1206 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 acceptable. Voltage derating can minimize this factor, but results may vary with package size and among specific manufacturers. Output capacitor size can be estimated at a switching frequency (FS) of 500kHz (worst case).
Efficiency (%)
72 SD3814-2R2 (77m)
69
66
63
2
5
8
11
14
17
20
LED Current (mA)
Figure 8: AAT1239-1 Efficiency for Different Inductor Types (VIN = 3.6V; Ten White LEDs in Series).
COUT =
IOUT * DMAX FS * VOUT
Selecting the Boost Capacitors
The high output ripple inherent in the boost converter necessitates 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 AAT1239-1 boost regulator. MLC capacitors of type X7R or X5R are
To maintain stable operation at full load, the output capacitor should be sized 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.
Manufacturer
Murata Murata Murata Murata Murata
Part Number
GRM188R60J225KE19 GRM188R61A225KE34 GRM21BR71E225KA73L GRM31CR71H225KA88 GRM31CR71H475K
Value (F)
2.2 2.2 2.2 2.2 4.7
Voltage Rating
6.3 10 25 50 50
Temp Co
X5R X5R X7R X7R X7R
Case Size
0603 0603 0805 1206 1206
Table 5: Recommended Ceramic Capacitors.
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1239-1.2008.10.1.2
PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
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 AAT1239-1 boost converter is shown in Figures 9 and 10. The following PCB layout guidelines should be considered: 1. Minimize the distance from Capacitor C1 and C2 negative terminal to the PGND pins. This is especially true with output capacitor C2, which conducts high ripple current from the output diode back to the PGND pins.
40V Step-Up Converter for 4 to 10 White LEDs
Minimize the distance between L1 to DS1 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 GND terminals of C1 and C2. 4. Consider additional PCB area on DS1 cathode to maximize heatsinking capability. This may be necessary when using a diode with a high VF and/or thermal resistance. 5. To avoid problems at startup, add a 10k resistor between the VIN, VP and EN/SET pins (R4). This is critical in applications requiring immunity from input noise during "hot plug" events, e.g. when plugged into an active USB port. 2.
Figure 9: AAT1239-1 Evaluation Board Top Side Layout (with ten LEDs and microcontroller).
Figure 10: AAT1239-1 Evaluation Board Bottom Side Layout (with ten LEDs and microcontroller).
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM 40V Step-Up Converter for 4 to 10 White LEDs
VCC
S2Cwire Microcontroller
R8 330
R7 1k
R6 1k
R5 1k
1 2
U2 PIC12F675
C3 0.1F
VDD GP5 GP4 GP3
VSS GP0 GP1 GP2
8 7 6 5
S1 Select S2 Down S3 Up
3 4
D12 Red
R9 330
D11 Green
JP2 R4 10k
JP3
DC-
DC+
U1 AAT1239-1
L1 10H
12
DS1 Schottky
VOUT R2 374k R3 12k JP4
D1 WLED D2 WLED D3 WLED D4 WLED
AAT1239-1 White LED Driver
C2 2.2F
C 10F
VCC 123 JP1
1 2
VIN EN 3 SEL
4
LIN 11 OVP 10 FB GND 8 PGND SW
7 9
C1 4.7F
5 6
VP N/C SW
R1 30.1
D10 WLED D9 WLED D8 WLED D7 D6 WLED WLED
D5 WLED
Figure 11: AAT1239-1 Evaluation Board Schematic (with ten LEDs and microcontroller).
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Additional Applications
Efficiency vs. LED Current
L1 2.2H DS1 Schottky R2 158k C2 2.2F Up to 17V/ 30mA max
D1 LED
40V Step-Up Converter for 4 to 10 White LEDs
(4 White LEDs; RBALLAST = 30.1)
84 83 82
PVIN
Li-Ion VIN = 2.7V to 5.5V C1 2.2F
LIN
VIN = 5V
Efficiency (%)
VIN
SW AAT1239-1 OVP
D2 LED D3 LED D4 LED
R3 12k
81 80 79 78 77 76 75 74 2 4 6 8 10 12 14 16 18 20
PGND EN/SET SEL FB AGND
R1 30.1 20mA
VIN = 4.2V
VIN = 3.6V
ILED (mA)
Figure 12: Four LEDs In Series Configuration.
Efficiency vs. LED Current
L1 2.2H DS1 Schottky R2 287k C2 2.2F Up to 30V/ 30mA max
D1 LED
(8 White LEDs; RBALLAST = 30.1) VIN = 5V
80 78
PVIN
Li-Ion VIN = 2.7V to 5.5V C1 2.2F
LIN
Efficiency (%)
VIN
SW AAT1239-1 OVP
D2 LED D3 LED D4 LED D5 LED
76 74 72 70 68 66 2 4 6 8 10 12 14 16 18 20
R3 12k
PGND EN/SET SEL FB AGND
R1 30.1 20mA
D8 LED D7 LED D6 LED
VIN = 4.2V
VIN = 3.6V
ILED (mA)
Figure 13: Eight LEDs In Series Configuration.
Efficiency vs. LED Current
L1 2.2H DS1 Schottky R2 324k C2 2.2F Up to 34V/ 30mA max
D1 LED
(9 White LEDs; RBALLAST = 30.1)
78 76
VIN = 5V
PVIN
Li-Ion VIN = 2.7V to 5.5V C1 2.2F
LIN
VIN
SW AAT1239-1 OVP
Efficiency (%)
D2 LED D3 LED D4 LED D5 LED
R3 12k
74 72 70 68 66
PGND EN/SET SEL FB AGND
R1 30.1 20mA
D9 LED D8 LED D7 LED D6 LED
VIN = 4.2V
VIN = 3.6V
2
4
6
8
10
12
14
16
18
20
ILED (mA)
Figure 14: Nine LEDs In Series Configuration.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
L1 10H
40V Step-Up Converter for 4 to 10 White LEDs
90.0
DS1 R2 374k C2 2.2F
D1 D2 D3 D4 D5 D6
87.5
PVIN
Li-Ion VIN = 3.0V to 4.2V C1 4.7F
LIN SW
Efficiency (%)
85.0 82.5 80.0 77.5 75.0 72.5 70.0 2 4 6 8 10 12 14 16 18 20
VIN AAT1239-1
R3 12k
OVP PGND EN/SET SEL
C1 10V 0805 X5R 4.7F GRM219R61A475KE19 C2 50V 1206 X7R 2.2F GRM31CR71H225KA88 L1 10H CDRH3D18-100NC DS1 SS16L
FB
D10 D9 D8 D7
AGND
R1 30.1
20mA
VIN = 3.0V VIN = 3.6V VIN = 4.2V
IOUT (mA)
Figure 15: Enhanced Efficiency Configuration for Li-ion Battery Ten WLEDs Series-Connected Application.
L1 4.7H
85.0
DS1
82.5
D2 D3 D4 D5 D12 D13 D14 D15 D16 D17 D18 D19 D20
Li-Ion VIN=3.0V to 4.2V
C1 4.7F
VIN
SW AAT1239 -1 OVP
R3 12k
C2 2.2F
Efficiency (%)
PVIN
LIN
R2 374k
D1
D11
80.0 77.5 75.0 72.5 70.0 67.5 65.0 5 10 15 20 25 30 35 40
PGND EN/SET SEL FB AGND
R1 15 40mA
D6 D7 D8
VIN = 3.0V VIN = 3.6V VIN = 4.2V
C1 10V 0805 X5R 4.7F GRM219R61A475KE19 C2 50V 1206 X7R 2.2F GRM31CR71H225KA88 L1 4.7H CDRH4D22/HP-4R7 DS1 SS16L
D9 D10
IOUT (mA)
Figure 16: Enhanced Efficiency Configuration for Li-ion Battery, Two Branch, Ten WLEDs Series-Connected Application.
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PRODUCT DATASHEET
AAT1239-1
SwitchRegTM
Ordering Information
Package
TSOPJW-12
40V Step-Up Converter for 4 to 10 White LEDs
Marking1
ZLXYY
Part Number (Tape and Reel)2
AAT1239ITP-1-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 Information
TSOPJW-12
0.10 0.20 + 0.05 -
2.40 0.10
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
2.85 0.20
7 NOM 3.00 0.10
0.9625 0.0375 + 0.10 1.00 - 0.065
0.04 REF 0.15 0.05 4 4
0.010
0.055 0.045
0.45 0.15 2.75 0.25
All dimensions in millimeters.
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.
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.
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