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High Current LED Flash Driver Charge Pump IC General Description
The AAT3170 is a high output current, high efficiency, low noise, low profile charge pump DC/DC converter, ideal for multi-function LED photo-flash applications where solution cost, size, and efficiency are critical. The dual charge pump in the AAT3170 is capable of delivering 600mA output current. Two currentcontrolled paths are available for users of dual flash LEDs that prefer current matching. Each LED channel can be easily programmed in 32 steps with a single GPIO output through the AS2CwireTM (Advanced Simple Serial ControlTM) interface. This allows smooth transitions and flexible adjustment of brightness in flash or other lighting modes. The tri-mode (1X/1.5X/2X) operation of the internal charge pump offers excellent power efficiency for both flash and movie modes. Combined with a low external parts count (two 1F flying capacitors and one small bypass capacitor at VIN and OUT), the AAT3170 is ideally suited for small, battery-powered applications. The AAT3170 has a thermal management system to protect the device in the event of a short-circuit condition at the output pin. Built-in soft-start circuitry prevents excessive inrush current during start-up. The shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1.0A. The AAT3170 is available in the Pb-free, thermallyenhanced, 12-pin 3x3mm TDFN package.
AAT3170
Features
* * * * * * * * * * * * * *
ChargePumpTM
VIN Range: 2.7V to 5.5V 600mA Output Current Tri-Mode 1X/1.5X/2X in Current Mode Voltage Mode Operation: 1.5X, 200mA Dual Regulated Current Sinks Current Match Between Current Sinks 32 Current Steps Set by AS2Cwire 1F Input, Output, and Flying Capacitors <1.0A of Shutdown Small Application Circuit No Inductors Automatic Soft Start 12-Pin TDFN 3x3mm Package -40C to +85C Temperature Range
Applications
* * * * Camera Phones Digital Still Cameras (DSCs) PDAs and Notebook PCs Smart Phones
Typical Application
C1 1F C2 1F
C1+
C1-
C2+
C2-
2.7V to 5.5V
C IN 4.7F
VIN
VOUT
AAT3170
C OUT 2.2F
Flash LED 1
Flash LED 2
EN/SET
EN/SET F1 CT
CT 0.1F
F2 GND
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High Current LED Flash Driver Charge Pump IC Pin Descriptions
Pin #
1, 12 2 3 4 5 6 7 8 9 10 11 EP
AAT3170
Symbol
VIN C1+ C1GND F1 F2 EN/SET CT C2C2+ VOUT
Function
Input power supply pin. Requires 4.7F or larger ceramic bypass capacitor to ground. Flying capacitor C1 positive terminal. Connect a 1F ceramic capacitor between C1+ and C1-. Flying capacitor C1 negative terminal. Ground connection. Current sink input #1. Current sink input #2. AS2Cwire serial interface control pin. Flash timer control capacitor input. Connect a 100nF capacitor from CT to GND for a one second timeout duration. Flying capacitor C2 negative terminal. Flying capacitor C2 positive terminal. Connect a 1F ceramic capacitor between C2+ and C2-. Charge pump output. Requires 2.2F or larger ceramic capacitor connected between this pin and ground. Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
TDFN33-12 (Top View)
VIN C1+ C1GND F1 F2
1 2 3 4 5 6
12 11 10 9 8 7
VIN VOUT C2+ C2CT EN/SET
2
3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC Absolute Maximum Ratings1
TA = 25C, unless otherwise noted. Symbol
VIN VEN VEN(MAX) IOUT TJ TS TLEAD
AAT3170
Description
Input Voltage EN to GND Voltage Maximum EN to Input Voltage Maximum DC Output Current Operating Junction Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6.0 -0.3 to 6.0 VIN + 0.3 700 -40 to 150 -65 to 150 300
Units
V V V mA C C C
Thermal Information2, 3
Symbol
JA PD
Description
Maximum 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. 2. Mounted on an FR4 board. 3. Derate 20mW/C above 40C ambient temperature. 3170.2006.11.1.1
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High Current LED Flash Driver Charge Pump IC Electrical Characteristics1
CIN = 4.7F, COUT = 2.2F, C1 = C2 = 1.0F; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C, VIN = 3.6V. Symbol Description Conditions Min
2.7 ON/OFF Standby Mode, Code Address = 4, Data = 2 1X, No Load Current 3.0 VIN 5.5, 1.5X Mode, No Load Current 3.0 VIN 5.5, 2X Mode, No Load Current EN = 0 VF = 3.6V VIN = 3.6V, TA = 25C, 428mA Code Address = 3, Data = 2; Code Address = 0, Data = 4 VIN = 3.6V, TA = 25C, 100mA Code Address = 3, Data =1; Code Address = 0, Data = 1 TA = 25C, Code 1, HI Scale EN/SET Code Address = 6, Data = 2 10 A 300 2.0 3.0 600 8 4.0 6.0 1.0 mA A mA %
AAT3170
Typ Max Units
5.5 V
Power Supply VIN Input Voltage Range
ICC
Operating Current
ISHDN(MAX) IOUT(MAX) I(D-Match) I(D-Match) IDX FCLK VREG TSS EN/SET VIL VIH TEN/SET LO TEN/SET HI MIN TEN/SET HI MAX TOFF TLAT Input Current
VIN Pin Shutdown Current Maximum Output Current Current Matching Between Outputs; High Current Current Matching Between Outputs; Low Current Output Current Accuracy Clock Frequency Voltage Mode Regulation Soft-Start Time
8 270 4.1 1 4.5 200 330 4.9
% mA MHz V s V V s ns s s s A
Enable Threshold Low VIN = 2.7V Enable Threshold High VIN = 5.5V EN/SET Low Time Minimum EN/SET High Time Maximum EN/SET High Time EN/SET Off Timeout EN/SET Latch Timeout EN/SET Input Leakage
0.4 1.4 0.3 50 75 500 500 1 75
-1
1. The AAT3170 is guaranteed to meet performance specifications from 0C to 70C. Specification over the -40C to +85C operating temperature range is assured by design, characterization, and correlation with statistical process controls.
4
3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC Typical Characteristics
VIN = 3.6V, CIN = 4.7F, COUT = 2.2F, C1 = C2 = 1F, TA = 25C, unless otherwise noted.
Efficiency vs. Supply Voltage
100 90 50mA/ch VF = 2.9V 152mA/ch VF = 3.2V
AAT3170
Turn-On to 1X Mode
(VIN = 4.2V; 50mA/ch Load)
Efficiency (%)
80 70 60 50 40 30 20
EN (2V/div) VOUT (2V/div) VSINK (1V/div) IIN (200mA/div)
95mA/ch VF = 3.1V
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
Supply Voltage (V)
Time (200s/div)
Turn-On to 1.5X Mode
(VIN = 3.2V; 50mA/ch Load)
Turn-On to 1X Mode
(VIN = 4.2V; 300mA/ch Load)
EN (2V/div) VOUT (2V/div) VSINK (1V/div) IIN (200mA/div)
EN (2V/div) VOUT (2V/div) VSINK (1V/div) IIN (500mA/div)
Time (200s/div)
Time (500s/div)
Turn-On to 2X Mode
(VIN = 3.2V; 300mA/ch Load) EN (2V/div) VF (1V/div)
Turn-Off from 1.5X Mode
(VIN = 3.2V; 50mA/ch Load)
EN (2V/div) VOUT (2V/div) VSINK (1V/div) IIN (500mA/div)
IIN (200mA/div)
Time (500s/div)
Time (200s/div)
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High Current LED Flash Driver Charge Pump IC Typical Characteristics
VIN = 3.6V, CIN = 4.7F, COUT = 2.2F, C1 = C2 = 1F, TA = 25C, unless otherwise noted.
Load Characteristic
(VIN = 3.0V; 1.5X Mode; 50mA/ch Load)
AAT3170
Load Characteristic
(VIN = 3.6V; 1.5X Mode; 152mA/ch Load)
VIN (100mV/div) VOUT (200mV/div) VSINK (200mV/div)
VIN (100mV/div) VOUT (200mV/div) VSINK (200mV/div)
Time (2s/div)
Time (2s/div)
Load Characteristic
(VIN = 2.8V; 2X Mode; 152mA/ch Load)
4.8
Voltage Mode Line Regulation
Output Voltage (V)
VIN (100mV/div) VOUT (200mV/div)
4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
IOUT = 10mA
IOUT = 80mA IOUT = 120mA
IOUT = 30mA
VSINK (200mV/div)
Time (2s/div)
Supply Voltage (V)
Voltage Mode Load Regulation
4.8 1.8 1.6
Flash Timer Duration
(CT = 0.1F; Data = 1)
Output Voltage (V)
4.7
Flash Time (s)
85C
4.6
1.4 1.2 1.0 0.8 0.6 0.4
VIN = 4.2V
4.5 4.4 4.3 4.2 0 50 100 150 200
VIN = 3.7V
25C -40C
VIN = 3.3V
250 300
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Load Current (mA)
Supply Voltage (V)
6
3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC Typical Characteristics
VIN = 3.6V, CIN = 4.7F, COUT = 2.2F, C1 = C2 = 1F, TA = 25C, unless otherwise noted.
Flash Timer Duration
(CT = 0.1F; Data = 16)
AAT3170
EN/SET Latch Timeout vs. Supply Voltage
EN/SET Latch Timeout (s)
350 300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
140 120
Flash Time (ms)
100 80 60 40 20
85C
-40C
25C
25C -40C
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
85C
Supply Voltage (V)
Supply Voltage (V)
EN/SET Off Timeout vs. Supply Voltage
EN/SET High Threshold Voltage (V)
350 1.0 0.9 0.8 0.7
EN/SET High Threshold Voltage vs. Supply Voltage and Temperature
-40C
EN/SET Off Timeout (s)
300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
-40C
25C
85C 25C
85C
0.6 0.5 0.4 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Supply Voltage (V)
Supply Voltage (V)
EN/SET Low Threshold Voltage (V)
EN/SET Low Threshold Voltage vs. Supply Voltage and Temperature
1.0 0.9 0.8 0.7 0.6 0.5 0.4 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
-40C
85C 25C
Supply Voltage (V)
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High Current LED Flash Driver Charge Pump IC Functional Block Diagram
C1+ C1C2+ C2-
AAT3170
VIN
Charge Pump Section 1 Charge Pump Section 2
1MHz Oscillator Soft Start Control
OUT
F1
EN/SET
System Control; AS 2Cwire; Timing
F2
GND
CT
Functional Description
The AAT3170 is a high efficiency, low noise, dual stage tri-mode 1X/1.5X/2X charge pump device intended for photo-flash LED applications. The AAT3170 requires only four external components: two 1.0F ceramic capacitors for the charge pump flying capacitors, one 4.7F ceramic capacitor for CIN, and one 2.2F ceramic capacitor for COUT. The charge pump is designed to deliver load currents up to 600mA. The dual stage charge pump section contains soft-start circuitry to prevent excessive in-rush current during start-up. System efficiency is maximized with a tri-mode, dual stage charge pump topology. The internal clock oscillator, which operates at 1MHz, allows the use of small external components. The tri-mode charge pump architecture optimizes power conversion efficiency. Depending upon the combination of load current, input voltage, and nominal LED forward voltage, the charge pump will 8
operate in a 1X, 1.5X, or 2X mode to generate the output voltage required to power the load for a programmed constant current setting. This results in significant power savings over voltage doubling architectures, especially when the LEDs are continuously operated at lower current levels in movie viewing or flashlight modes.
Constant Current Channels
The AAT3170 contains two programmable constant current sinks for integrated flash circuit control. Efficiency is optimized with the low dropout characteristic of the current sinks. The low dropout performance extends the battery operating range for 1X and 1.5X modes, improving efficiency and extending battery life. Each constant current sink is programmable through the AS2Cwire serial interface. Independent current settings can be used for a multistage flash LED control. This feature allows users to conveniently drive separate dual flash LEDs directly while achieving good brightness
3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC
matching. Also, F1 and F2 can be connected together for single output configuration. The AAT3170 also includes a regulated output voltage mode setting. By setting Register 6 with Data = 2 for voltage mode, the charge pump delivers a regulated 4.5V output that continuously operates in 1.5X mode. It is suitable for driving loads of up to 200mA. The voltage mode may be used to drive LEDs with ballast resistors. Driving either F1 or F2 in current mode will override the voltage mode state until F1 and F2 are set back to zero current by either data or mode register. Setting Register 5 with Data = 1 will reset the mode back to current mode and the charge pump output voltage will regulate appropriately.
AAT3170
Modes of Operation
In addition to the data registers that set the current levels for the two current sinks, the AAT3170 has three mode registers. Register 3 is the HI/LO mode register. It sets the maximum per channel current level to either 300mA or 50mA. Each channel can be set independently so one channel can be for flash while the other can be in a low constant current mode. Register 4 is the ON/OFF register. When set with Data = 1, both current sources are enabled (default); when set with Data = 2, both current sources are disabled. When Register 4 is set to OFF, the device is in standby mode with significantly reduced quiescent current. The AAT3170 has a software programmable timer function to automatically adjust the flash on-time duration. This feature can be used directly to set the flash on-time, or it can be used indirectly for fault tolerant flash protection. When used for flash protection, the user can be sure that the flash will still turn off in the event of any system software or hardware malfunction. Write to Address 5 to enable the flash timer and flash channels. When the timer register is addressed and data is latched, the ON/OFF register is automatically switched to ON, enabling the current sinks for the duration of the programmed time. When the timer expires, the ON/OFF register is switched to OFF, disabling the current sinks. The on-time T depends on the combination of the setting of the timer register and the value of the timing capacitor, which are listed in the "Timer Register" table. Calculate the timer capacitor value according to the following formula:
AS2Cwire Serial Interface
The AAT3170 utilizes the AS2Cwire serial interface to enable/disable the charge pump, set the operating mode, and adjust the output current level of each constant current sink. Each current sink can be independently programmed with sixteen current levels (see table below). AS2Cwire incorporates addressing to program the operating modes and current level settings.
Constant Current Sink Nominal Programming Levels
Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
300mA HI Scale ISINK (mA/chnl)
300 267 238 214 190 167 152 133 119 105 95 86 76 67 62 0
50mA LO Scale ISINK (mA/chnl)
50 44 40 36 32 28 25 22 20 17 16 14 13 11 10 0
T (seconds) = 10 * CT (F)
where CT is in micro-farads. For example, using a 0.1F timer capacitor value results in an on-time duration of one second.
AS2Cwire relies on the number of rising edges of the EN/SET pin to address and load the registers.
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High Current LED Flash Driver Charge Pump IC
AS2Cwire latches data or address after the EN/SET pin has been held high for time TLAT (500s). Address or data is differentiated by the number of EN/SET rising edges. Since the data registers are 4 bits each, the differentiating number of pulses is 24 or 16, so that Address 0 is signified by 17 rising edges, Address 1 by 18 rising edges, and so forth. Data is set to any number of rising edges between 1 and including 16. A typical write protocol is a burst of EN/SET rising edges, signifying a particular address, followed by a pause with EN/SET held high for the TLAT timeout period, a burst of rising edges signifying data, and a TLAT timeout for the data registers. Once an address is set, then multiple writes to that address are allowed where only data is issued. When EN/SET is held low for an amount of time greater than TOFF (500s), the AAT3170 enters into shutdown mode and draws less than 1A from the supply. Address 0 is the default address on the first rising edge after the AAT3170 has been disabled. After shutdown, if only data is issued with the first rising edge (i.e., 1 - 16 edges, no address given), both current sinks will be programmed since the default will be Address 0.
AAT3170
ON/OFF Register (Address 4)
Data
1 2
MODE
ON OFF
Timer Register (Address 5)
Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
On-Time T (sec) = 10 * CT (F)
16/16 x T 15/16 x T 14/16 x T 13/16 x T 12/16 x T 11/16 x T 10/16 x T 9/16 x T 8/16 x T 7/16 x T 6/16 x T 5/16 x T 4/16 x T 3/16 x T 2/16 x T 1/16 x T
AS2Cwire Serial Interface Addressing
EN/SET Address Rising Edges
0 1 2 3 4 5 6 17 18 19 20 21 22 23
Data Register
F1 and F2 Current Scale F1 Current Scale F2 Current Scale HI/LO ON/OFF Timer Voltage/Current Mode
Voltage Register (Address 6)
Data
1 2
MODE
Current Voltage
Thermal Protection
The AAT3170 has a thermal protection circuit that will shut down the charge pump if the die temperature rises above the thermal limit, as is the case during a short circuit of the OUT pin.
HI/LO Scale Register (Address 3)
Data
1 2 3 4
F1
LO HI LO HI
F2
LO HI HI LO
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3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC
AS2Cwire Serial Interface Timing
Address
T HI T LO TLAT TLAT
AAT3170
Data
EN/SET
1 2 17 18 1 2... n <= 16
Address
0
1
Data Reg 1
0
n-1
Data Reg 2
0
Applications Information
AS2Cwire Programming
Generally, programming the AAT3170 is achieved by submitting bursts of address and data edges to the EN/SET pin. However, in some cases multiple bursts of address and data are needed to enable a particular operating mode. In other cases, only a single burst of data edges is required. To enable both flash channels to a current setting on the LO scale, the user submits a single burst of address and data edges. To enable both flash channels to a current setting on the HI scale, the user must submit a burst of address and data edges to program the current setting level, and then submit a second burst of address and data edges to program the HI/LO scale register to the HI scale. Shortcuts can also be used. If the device is in shutdown, both flash channels can be enabled to a setting on the LO scale by just giving a single burst of data edges. The address edges are not needed because all registers are reset during shutdown and address 0 is the default. Further, a single burst of data edges can be used to change from one set-
ting to another for the last address. The address register is not reset after each write; therefore, submitting address edges is only required when changing the address.
Additional Applications
The constant voltage mode feature of the AAT3170 allows the user to combine the flash feature with additional applications. Additional applications such as auxiliary lighting and status LEDs can be added while eliminating the need for an additional power supply, which is normally required. Since the constant voltage mode can supply a regulated output at up to 200mA load, it is capable of driving ten LEDs at 20mA each. It is suitable for keypad lighting, status lighting, and other applications where a 4.5V power supply could be used. When enabling constant voltage mode, the LED channels F1 and F2 are automatically disabled so current does not flow through the flash LED during constant voltage mode. Because of this, very little programming is required. The user just addresses the voltage mode register and programs it to voltage mode.
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High Current LED Flash Driver Charge Pump IC
C1 1F C2 1F
AAT3170
C1+
C1-
C2+
C2-
2.7V to 5.5V
C IN 4.7F
VIN
VOUT
AAT3170
C OUT 2.2F
Flash LED
EN/SET
EN/SET CT GND
F1 F2 AUX_EN
Figure 1: Flash Plus Auxiliary Lighting.
C1 1F C2 1F
C1+
C1-
C2+
C2+
2.7V to 5.5V
CIN 4.7F
VIN
VOUT
AAT3170
C OUT 2.2F
Flash LED
EN/SET
EN/SET CT GND
F1 F2
STAT1
STAT2
Figure 2: Flash Plus Status Lighting.
LED Selection
The AAT3170 is designed to drive high-intensity white LEDs. It is particularly suitable for LEDs with an operating forward-voltage in the range of 4.2V to 1.5V. The charge pump device can also drive other loads that have similar characteristics to white LEDs. For various load types, the AAT3170 provides a high-current, programmable ideal constant current source.
Device Power Efficiency
The AAT3170 power conversion efficiency depends on the charge pump mode. By definition, device efficiency is expressed as the output power delivered to the LED divided by the total input power consumed.
=
POUT PIN
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3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC
When the input voltage is sufficiently greater than the LED forward voltage, the device optimizes efficiency by operating in 1X mode. In 1X mode, the device is working as a bypass switch and passing the input supply directly to the output. The power conversion efficiency can be approximated by:
VF * ILED VF VIN * IIN VIN
AAT3170
Capacitor Selection
Careful selection of the four external capacitors (CIN, C1, C2, and COUT) is important because they will affect turn-on time, output ripple, and transient performance. Optimum performance will be obtained when low equivalent series resistance (ESR) (<100m) ceramic capacitors are used. A value of 1F for the flying capacitors is a good starting point when choosing capacitors. If the LED current sinks are only programmed for light current levels, then the capacitor size may be decreased. Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3170. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is lowest cost, has a smaller PCB footprint, and is non-polarized. Low ESR ceramic capacitors help maximize charge pump transient response.
=
Due to the very low 1X mode quiescent current, the input current nearly equals the current delivered to the LED. Further, the low-impedance bypass switch introduces negligible voltage drop from input to output. The AAT3170 further maintains optimized performance and efficiency by detecting when the input voltage is not sufficient to sustain LED current. The device automatically switches to 1.5X mode when the input voltage drops too low in relation to the LED forward voltage. In 1.5X mode, the output voltage can be boosted to 3/2 the input voltage. The 3/2 conversion ratio introduces a corresponding 1/2 increase in input current. For ideal conversion, the 1.5X mode efficiency is given by:
VF VF * ILED = VIN * 1.5IIN 1.5 * VIN
Equivalent Series Resistance
ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors.
=
Similarly, when the input falls further, such that 1.5X mode can no longer sustain LED current, the device will automatically switch to 2X mode. In 2X mode, the output voltage can be boosted to twice the input voltage. The doubling conversion ratio introduces a corresponding doubling of the input current. For ideal conversion, the 2X mode efficiency is given by:
VF VF * ILED = VIN * 2IIN 2 * VIN
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F are typically made from NPO or C0G materials. NPO and C0G materials typically have tight tolerance and are stable over temperature. Large capacitor values are typically composed of X7R, X5R, Z5U, or Y5V dielectric materials. Large ceramic capacitors are often available in lower-cost dielectrics, but capacitors greater than 4.7F are not typically required for AAT3170 applications. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when compared to an equivalent material, smaller capacitor. These larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size.
=
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High Current LED Flash Driver Charge Pump IC
PCB Layout
To achieve adequate electrical and thermal performance, careful attention must be given to the PCB layout. In the worst-case operating condition, the chip must dissipate considerable power at full load. Adequate heat-sinking must be achieved to ensure intended operation. Figure 3 illustrates an example of an adequate PCB layout. The bottom of the package features an exposed metal paddle. The exposed paddle acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. The junction-to-ambient thermal resistance (JA) for the package can be significantly reduced by following a couple of important PCB design guidelines. The PCB area directly underneath the package should be plated so that the exposed paddle can be mated to the top layer PCB copper during the re-flow process. This area should also be connected to the top layer ground pour when available. Further, multiple copper plated thru-holes should be used to electrically and thermally connect the top surface paddle area to additional ground plane(s) and/or the bottom layer ground pour. The chip ground is internally connected to both the paddle and the GND pin. The GND pin conducts large currents and it is important to minimize any differences in potential that can result between the GND pin and exposed paddle. It is good practice to connect the GND pin to the exposed paddle area using a trace as shown in Figure 3. The flying capacitors C1 and C2 should be connected close to the chip. Trace length should be kept short to minimize path resistance and potential coupling. The input and output capacitors should also be placed as close to the chip as possible.
AAT3170
Figure 3: Example PCB Layout.
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3170.2006.11.1.1
High Current LED Flash Driver Charge Pump IC Ordering Information
Package
TDFN33-12
AAT3170
Marking1
QLXYY
Part Number (Tape and Reel)2
AAT3170IWP-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/pbfree.
Package Information
TDFN33-12
Index Area (D/2 x E/2) Detail "B"
3.00 0.05
2.40 0.05
0.3 0.10 0.16 0.375 0.125 0.075 0.075 0.1 REF
Top View
Bottom View
Pin 1 Indicator (optional)
7.5 7.5
+ 0.05 0.8 -0.20
0.229 0.051
0.05 0.05
Option A: C0.30 (4x) max Chamfered corner
Option B: R0.30 (4x) max Round corner
Detail "B"
Side View
All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.
(c) Advanced Analogic Technologies, Inc.
Detail "A"
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. Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737- 4600 Fax (408) 737- 4611
3170.2006.11.1.1
0.23 0.05
0.45 0.05
Detail "A"
3.00 0.05
1.70 0.05
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