A6210GEUTR-T

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The A6210 is a buck regulator that uses valley current-mode control. This control scheme allows very short switch on-times to be achieved, making it ideal for applications that require high switching frequencies combined with high input voltages and low output LED span voltages. Low system cost is accomplished through high switching frequencies of up to 2.0 MHz, allowing smaller and lower value inductors and capacitors. In addition, few external components are required through high levels of integration. Optimal drive circuits minimize switching losses. The switching frequency is maintained constant, as the on-time is modulated by the input voltage. This feed-forward control ensures excellent line correction. The on-time is set by an external resistor pulled-up to the input supply. Internal housekeeping and bootstrap supplies are provided which require the addition of only one small ceramic capacitor. A top-off charge pump ensures correct operation at light loads. Internal diagnostics provide comprehensive protection against input undervoltages and overtemperatures. The device package is a 16-contact, 4 mm × 4 mm, 0.75 mm nominal overall height QFN, with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte tin leadframe plating. 6210-DS, Rev. 1 Features and Benefits ▪ User-configurable on-time, achieving switching frequencies up to 2.0 MHz ▪ Brightness control through PWM of DIS pin ▪ Minimal external components required ▪ No output capacitor required ▪ Wide input voltage range: 9 to 46 V ▪ Low 0.18 V sense voltage for higher efficiency ▪ Output Current: up to 3.0 A ▪ Low standby current <100 μA ▪ Thermal shutdown ▪ Supplied in a thermally-enhanced 4 mm QFN package

3 A, 2 MHz Buck-Regulating LED Driver

Applications: Typical Application A6210 GNDNC L D1 LED1 LED2 LED3 68 μH LX VIN ISEN SGND A6210 TON 22 nF 150 kΩ 1.0 μF 390 mΩ DIS PWM or Switch C2BOOT VIN 24 V LED span voltage = 10.5 V Average LED current = 500 mA Peak to peak current = 60 mA Switching frequency = 1.4 MHz Efficiency = 90.5% Package 16-contact QFN (suffix EU): ▪ High brightness LEDs ▪ LED driver modules, power supplies and lamps, such as MR16 and MR11 4 mm × 4 mm × 0.75 mm Suggested Parts Name Description Manufacturer - Part Number C1 1 μF, 25V, X5R or X7R ceramic, 1210 Taiyo Yuden, TDK C2 22 nF, 50V, X5R or X7R ceramic, 0805 D1 1 A, 30 V, Schottky diode L1 68 μH, 1 A inductor Taiyo Yuden - NR 6045T 680M R1 180 k Ω, 1%, 0805 R2 390 m Ω, 1%, 0805

3 A, 2 MHz Buck-Regulating LED DriverA6210

2Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A. Absolute Maximum Ratings (reference to GND) Characteristic Symbol Notes Rating Units VIN Pin Supply Voltage V IN –0.3 to 50 V LX Pin Switching Node Voltage V LX –1 to 50 V ISEN Pin Current Sense Voltage V ISEN –1.0 to 0.5 V DIS Pin Disable Voltage V DIS –0.3 to 7 V TON Pin On-Time Voltage V TON –0.3 to 50 V Operating Ambient Temperature T A Range G –40 to 105 ºC Maximum Junction Temperature T J(max) 150 ºC Storage Temperature T stg –55 to 150 ºC Selection Guide Part Number Packing Package A6210GEUTR-T 1500 pieces per reel 16-contact 4 mm × 4 mm QFN with exposed thermal pad Thermal Characteristics may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions* Value Units Package Thermal Resistance, Junction to Ambient RθJA On 4-layer PCB based on JEDEC standard 36 ºC/W Package Thermal Resistance, Junction to Pad RθJP On 4-layer PCB based on JEDEC standard 2 ºC/W *Additional thermal information available on the Allegro website. Recommended Operating Conditions Characteristic Symbol Conditions Min. Typ. Max. Units Supply Voltage V IN 9 – 46 V Switching Node V LX –0.7 – 46 V Switching Frequency Range f SW Continuous conduction mode 0.1 – 2.0 MHz Operating Ambient Temperature T A –40 – 105 ºC Junction Temperature T J –40 – 125 ºC

3Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Reg Ref Control Logic On Timer Regulator Comparator Off Timer Driver Linear Regulator Fault VIN UVLO TSD Linear OK VIN DIS GND TON BOOT LX ISEN VIN 24 V VIN Sleep Circuit SGNDSwitch Closed = On NC 1.0 μF 68 μH 390 mΩ Blank Top-off Charge Pump 22 nF 180 kΩ Switching Frequency = 1.4 MHz All capacitors are X5R or X7R ceramic Resistor R2 should be surface mount, low inductance type, rated at 250 mW at 70°C LED1 LED2 LED3 Functional Block Diagram Pin-out Diagram Terminal List Table Number Name Function

1 VIN Input supply

2, 7, 13, 14, 15, 16 NC No connection; tie to GND

3 TON Terminal for on-time setting with external resistor

4, 5, 6 GND Ground terminal

8 ISEN Current sense input

9 SGND Current sense ground reference

10 DIS Disable/enable logic input; active high

11 BOOT Bootstrap supply node

12 LX Switch node

–P A D Exposed thermal pad; connect to ground plane (GND) by through-hole vias NC NC NC NC GND GND NC ISEN LX BOOT DIS SGND PAD VIN NC TON GND (Top View)

4Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. ELECTRICAL CHARACTERISTICS* valid at TJ = 25°C, VIN = 9 to 46 V, unless otherwise noted Characteristic Symbol Conditions Min. Typ. Max. Units General VIN Quiescent Current I VINOFF DIS = high, VIN = 46 V – – 100 μA Current Sense Voltage V SENSE 176 183 190 mV On-Time Tolerance ∆TON Based on selected value –15 – 15 % Minimum On-Time Period T on(min) – 50 60 ns Minimum Off-Time Period T off(min) – – 350 ns Start-Up Time t START Using application circuit on page 1; time from application of ¯D¯ ¯I¯ ¯S¯ (enable) to reaching target current –1 5– μs Buck Switch On-Resistance R DS(on) TJ = 25°C, ILOAD = 3 A – 350 – m Ω TJ = 125°C, ILOAD = 3 A – 550 – m Ω Input DIS Input Voltage Threshold V DIS Device enabled – – 1 V DIS Open-Circuit Voltage V DISOC Device disabled 2 – 7 V DIS Input Current I IN DIS = 0 V –10 – –1 μA Protection VIN Undervoltage Shutdown Threshold V INUV Voltage rising 6.3 – 7.5 V VIN Undervoltage Shutdown Hysteresis V INUV(hys) 0.7 – 1.1 V Overtemperature Shutdown Threshold T JTSD Temperature rising – 165 – °C Overtemperature Shutdown Hysteresis T JTSD(hys) Recovery = TJTSD – TJTSD(hys) – 15 – °C *Specifications over the junction temperature range of –40°C to 125°C are assured by design and characterization.

5Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Basic Operation The A6210 is a buck regulator that utilizes valley current mode control. The on-time is set by the amount of current that flows into the TON pin. This is determined by the value of the TON resistor chosen (R1 in the Functional Block diagram) and the magnitude of the input voltage, V IN. Under a specific set of conditions, an on-time can be set that then dictates the switching frequency. This switching frequency remains reasonably con- stant throughout load and line conditions as the on-time varies inversely with the input voltage. At the beginning of the switching cycle, the buck switch is turned on for a fixed period that is determined by the current flowing into TON. Once the current comparator trips, a one-shot mono- stable, the On Timer, is reset, turning off the switch. The current through the inductor then decays. This current is sensed through the external sense resistor (R2), and then compared against the current-demand signal. After the current through the sense resis- tor decreases to the valley of the current-demand signal, the On Timer is set to turn the buck switch back on again and the cycle is repeated. Disable/Enable The regulator is enabled by pulling the DIS pin low. To disable the regulator, the DIS pin can simply be discon- nected (open circuit). Shutdown The regulator is disabled in the event of either an overtemperature event, or an undervoltage on VIN (V INUV) or on an internal housekeeping supply. As soon as any of the above faults have been removed and assuming DIS = 0, the output is restored. Switch On Time and Switching Frequency The switch on-time effectively determines the operating frequency of the converter. To minimize the size of the power inductor and input filtering it is recommended to run with as high a frequency as possible. The MOSFET drivers are optimized to minimize switching losses. An important consideration in selecting the switching frequency is to ensure that the on time (60 ns) and off time (350 ns) limita- tions are not reached under extreme conditions:

• the minimum on time occurs at maximum input voltage
• the maximum off time occurs at minimum input voltage The following table takes into account the above maximum off time figure and outlines the typical switching frequencies that can be achieved for a given number of LEDs and input voltage. Note that it is highly recommended that worst case values are used when considering any design. Switching Frequency (MHz) Input Voltage

12 V 24 V 36 V

(V) Quantity of LEDs LED Span Voltage (V) Quantity of LEDs LED Span Voltage (V) 2.0 1 3.5 2 7.0 3 10.5 1.7 1 3.5 3 10.5 4 14.0 1.0 2 7.0 4 14.0 6 21.0 0.300 3 10.5 6 21.0 9 31.5 The switch on time is programmed by the current flowing into the TON pin. The current is determined by the input voltage, VIN , and the resistor, R1. The on time, Ton , can be found: Ton = .VIN × 2.05 × 1010 10 × 10–9R1 + (1) To calculate the actual switching frequency, fsw , the Ton from the above calculation can be used in conjunction with the transfer function of the converter, as follows: fSW = .×VOUT + Vf VIN + Vf Ton (2) A simplified approach to selecting the Ton resistor (R1), to accomplish an approximate switching frequency, can be found from the following formula: R1 fSW = .VIN × 2.05 × 1010 (3) Figure 1 illustrates a range of switching frequencies that can be achieved with a given resistor and LED voltage. Each LED is assumed to have a voltage drop of 3.5 V . High Brightness LED Driving The A6210 can be configured as a very simple, low cost, high brightness LED driver. The solution can drive high brightness LEDs up to more than 3 A, while achieving very high efficien- cies, in excess of 90%. The solution uses valley current mode control. This architecture is optimized for high switching frequencies, allowing the use Functional Description

Worcester, Massachusetts 01615-0036 U.S.A. able/Enable) pin. See figure 4. the inductor ripple current, as shown in figure 2. not develop a ripple voltage of less than 20 mV . sense voltage (183 mV) divided by the sense resistor.

3 LEDs producing VLED = 12 V ,

LED ripple current, IRIPPLE = 60 mA . Figure 2. Current controlFigure 1. Switching frequency versus value of external resistor R1 on the

1 LED

2 LEDs

3 LEDs

4 LEDs

5 LEDs

7Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. off-time of 350 ns. A minimum off-time is required to ensure the bootstrap supply operates correctly. It can be shown that: fSW = ,toff (min) 1 – D (8) where toff is 350 ns maximum. Therefore: fSW == .350 × 10–9 1.4 MHz1 – 0.51 The ton resistor (R1) value can be found: R1 = VLED × 2.051 × 1010 fSW 1.4 × 106 176 × 103 . (9) Choose R1 = 180 kΩ. The inductor (L1) can now be found using the target LED ripple current of 60 mA: L1 = (VIN – VLED) × D IRIPPLE × fSW 60 × 10–3 × 1.4 × 106 72 × 10–6 . (10) Choose L1 = 68 μH. The inductor current rating should exceed the average current plus half of the ripple current. In addition, it is recommended that a margin of at least 20% be allowed. In this example, the inductor current rating, IL , should be: The valley control current is simply the average LED current minus half the ripple current. Therefore: IVALLEY = IRIPPLE = = 2 .60 × 10–3 500 × 10–3 – 470 mA Iav – (11) The sense resistor (R3) value can be found: R3 = VSENSE IVALLEY ==183 × 10–3 470 × 10–3 0.36 . (12) Choose R3 = 390 mΩ. The ripple voltage developed across the sense resistor (R2) is 60 mA × 390 mΩ = 23 mV , which is greater than the minimum required value of 20 mV . Measured switching waveforms From figure 3, it can be seen that the average current through the LED string is 484 mA. This represents an error of 3.2% with respect to the target current of 500 mA.

Worcester, Massachusetts 01615-0036 U.S.A. Figure 4. PWM on DIS pin at 400 Hz: (A) narrow duty cycle, (B) wide duty cycle. Figure 3. Switching voltage versus current through L1 and LED string

9Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. TON DIS PWM or Switch GNDNC L 47 μH LX VIN ISEN SGND A6210 22 nF 910 kΩ 1.0 μF 150 mΩ C2BOOT VIN 42 V 910 kΩ LED Assembly Average LED current = 1.34 A Peak to peak current = 200 mA LED Assembly voltage = 24 V Switching frequency = 1.0 MHz Efficiency = 90.5% Other Application Circuits Application Circuit 1 Suggested Parts Name Description Manufacturer - Part Number C1 1 μF, 25V, X5R or X7R ceramic, 1210 Taiyo Yuden, TDK C2 22 nF, 50V, X5R or X7R ceramic, 0805 D1 3 A, 60 V, Schottky diode L1 47 μH, 1.4 A inductor Taiyo Yuden - NR 8040T 470M R1, R3 910 k Ω, 1%, 0603 R2 150 m Ω, 1%, 1206 Plot 1. Average current = 1.34 A Plot 2. Peak to peak current = 200 mA Plot 3. PWM frequency = 10 kHz, maximum duty cycle Plot 4. PWM frequency = 10 kHz, minimum duty cycle Plot 5. Plot 4 with expanded time scale Plot 6. PWM frequency = 10 kHz, turn off Channel 1 – Current through inductor and LED Assembly, Channel 2 – Main switching voltage (LX node)

10Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. LED Assembly GNDNC L 22 μH LX VIN ISEN SGND A6210 TON 22 nF 310 kΩ 1.0 μF 150 mΩ DIS PWM or Switch 180 mΩ C2BOOT VIN 24 V Average LED current = 2.4 A Peak to peak current = 260 mA LED Assembly voltage = 15 V Switching frequency = 1.0 MHz Efficiency = 94% Application Circuit 2 Suggested Parts Name Description Manufacturer - Part Number C1 1 μF, 25V, X5R or X7R ceramic, 1210 Taiyo Yuden, TDK C2 22 nF, 50V, X5R or X7R ceramic, 0805 D1 3 A, 60 V, Schottky diode L1 22 μH, 2.8 A inductor Coilcraft - MSS1048-223ML R1 310 k Ω, 1%, 0603 R2 150 m Ω, 1%, 0805 R4 180 m Ω, 1%, 0805 Channel 1 – Current through inductor and LED Assembly, Channel 2 – Main switching voltage (LX node) Plot 1. Average current = 2.4 A Plot 2. Peak to peak current = 260 mA Plot 3. PWM frequency = 10 kHz, maximum duty cycle Plot 4. PWM frequency = 10 kHz, minimum duty cycle Plot 5. Plot 4 with expanded time scale Plot 6. PWM frequency = 10 kHz, turn off

11Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Package EU, 16-Contact QFN For the latest version of this document, visit our website: www.allegromicro.com Copyright ©2008-2009, Allegro MicroSystems, Inc. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. 0.95 CSEATING PLANEC0.08 17X A Terminal #1 mark area Coplanarity includes exposed thermal pad and terminals B Exposed thermal pad (reference only, terminal #1 identifier appearance at supplier discretion) For Reference Only (reference JEDEC MO-220WGGC) Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown C D D C Reference land pattern layout (reference IPC7351 QFN65P400X400X80-17W2M) All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) 4.10 0.35 0.65 4.10 0.65 0.40 ±0.10 2.70 2.70 4.00 ±0.15 4.00 ±0.15 2.70 2.70 B PCB Layout Reference View