AT7576 2A Step Down Voltage Regulator with Operational Amplifier

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1 FEATURES DESCRIPTION Output oltage Range, 1.23 to 37 ±3% Guaranteed 2A Output Current Wide Input oltage Range, 40 52KHz Fixed Frequency Oscillator TTL Shutdown capability, Low Power Standby Mode High Efficiency Thermal Shutdown and Current Limit Protection Low Input Offset oltage and offset Current of OpAmp for OCP Internal Frequency Compensation of OpAmp Over oltage Protect (OP) APPLICATION Car Charger with OP and OCP The AT7576 allows introducing an additional adjustment for the Over Current Protection (OCP) and Over oltage Protection (OP). In this case the OCP and OP value can be changed with help external resistors. The AT7576 provides all the active functions for a step-down (buck) switching regulator and is capable of driving 2A load with excellent line and load regulation. It includes an internal frequency compensation components and a fixed-frequency oscillator. Among other features are a guaranteed ±3% tolerance on an output voltage within the specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 120μA (Typical) standby current. The output switch includes cycle-by-cycle current limiting and thermal shutdown elements for a full protection under fault conditions. The high gain, internally frequency-compensated operational amplifiers were designed specifically to operate from a single power supply over a wide range of voltages. ORDER INFORMATION AT X.X SF8 R PIN CONFIGURATIONS (TOP IEW) IAT Circuit Type Output oltage: A: ADJ; 5.0: 5.0 Shipping: R: Tape & Reel SF8: PSOP-8 1

2 PIN DESCRIPTIONS Pin Name IN Input supply voltage. Pin Description ON /OFF ON/OFF Shutdown. Active is Low or floating. GND FB SW OP CCN CCP Thermal Pad Ground. Output voltage feedback. Switching Output. Over voltage protection. CC-Amp-inverting input. CC-Amp-noninverting input. Pad for heatsinking purpose. Connect to ground plane using multiple vias. Not electrically connected internally. TYPICAL APPLICATION CIRCUIT OUT FB (R1 R2) R2 R3 OCP I OUT OCP Rs R4 Figure 1: AT7576-ASF8 BLOCK DIAGRAM 2

3 ABSOLUTE MAXIMUM RATINGS (Note1) Parameter Symbol Max alue Unit Maximum supply oltage CC 45 FB Pin oltage FB IN ON/OFF Pin oltage ON/OFF IN Output Pin oltage OUT -1 + IN +0.3 Maximum Junction Temperature T J(max) 150 C Input Differential voltage Range idr 45 Input Common Mode voltage Range icr -0.3 to +45 Lead Temperature (Soldering, 5sec) T LEAD 260 C Power Dissipation P T A =25 C Thermal Resistance (Note 2) PSOP-8(Exposed Pad) P D 2770 mw PSOP-8 Θ JA 36 C /W Thermal Resistance PSOP-8 Θ JC 5.5 C /W ESD Rating (Human Body Model) (Note 3) ESD 2 k RECOMMENDED OPERATING CONDITIONS (Note 4) Parameter Symbol Operation Conditions Unit Supply oltage IN 5 to 40 Operating Junction Temperature Range T J -40 to +125 C Operating Ambient Temperature Range T A -40 to +85 C Note 1: Stresses listed as the above Absolute Maximum Ratings may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2: 2 square inch of FR-4, double sided, 1 oz. minimum copper weight. Note 3: Devices are ESD sensitive. Handling precaution recommended. Note 4: The device is not guaranteed to function outside its operating conditions. 3

4 ELECTRICAL CHARACTERISTICS Unless otherwise specified, IN =12. Note: T A =25 C. * denotes the specifications, which apply over full operating temperature range T J =-40 C to +125 C. Parameter OUT AT7576-ADJ Tolerance of OUT AT7576-ADJ Efficiency OUT AT Symbol OUT Condition Note Min Typ Max Unit SYSTEM PARAMETERS IN =12, I LOAD = 0.5A OUT programmed for 5 AT7576 (Note 5, 13) IN 40, 0.5A I LOAD 2A OUT programmed for 5 * TOL IN =10-30, I LOAD =0.5-2A % η OUT IN =12, I LOAD =2A OUT programmed for 5 77 % IN =12, I LOAD = 0.5A IN 40, 0.5A I LOAD 2A DEICE PARAMETERS * Feedback Bias Current I FB OUT =5, FB =1.3, CCN - CCP =0.1 * 500 Oscillator Frequency F OSC (Note 10) Saturation oltage SAT I OUT =2A (Note 6) * * 1.35 Max Duty Cycle (ON) DC (Note 7) % Current Limit I CL Peak Current (Note 6, 10) SW Leakage Current ON /OFF Pin Logic Input Level ON /OFF Pin Input I OL IH IL I IH * (Note 8, 9) SW = SW = OUT =0 OUT = nominal output voltage * * 0.8 khz ON /OFF pin = μa Current I IL ON /OFF pin = μa A ma 4

5 ELECTRICAL CHARACTERISTICS (CONTINUED) Unless otherwise specified, IN =12. Note: T A =25 C. * denotes the specifications, which apply over full operating temperature range T J =-40 C to +125 C. Parameter High oltage Threshold OP Pin Low oltage Threshold OP Pin Symbol OP H (Note 11) OP Pin Input current I OP OP =1.3 Input Offset oltage Average Temperature Coefficient of Input Offset oltage Condition Note Min Typ Max Unit DEICE PARAMETERS AT7576 (Note 5, 13) * 1.35 OP L (Note 11) 0.74 io αio Input Offset Current Iio CM = 0 Average Temperature Coefficient of Input Offset Current Input Bias Current Iib CM = 0 Common-Mode Input oltage Range High Level Output oltage Low Level Output oltage Common-Mode Rejection Ratio Power Supply Rejection Ratio OPERATIONAL AMPLIFIER CC-AMP * 500 CC = 5 to m ic = 0, FB =1.5 * u/ C CC = 5 to 40 ic = 0, FB =1.5 * 10 μ/ C * 300 αi io * 20 pa/ C icr FB_H FB_L CC = 5 to * -800 * 0 to CC to CC - R L 15K, CC = (Note 12) * 37 R L 10K * 30 CMRR ic =0 to IN db PSRR db m 5

6 ELECTRICAL CHARACTERISTICS (CONTINUED) Unless otherwise specified, IN =12. Note: T A =25 C. * denotes the specifications, which apply over full operating temperature range T J =-40 C to +125 C. Parameter Output Current Short-Circuit Output Current to GND Symbol Io Condition Note Min Typ Max Unit AT7576 (Note 5, 13) OPERATIONAL AMPLIFIER CC-AMP CC = 12, io=1, FB =1.5 * I SC FB =0, io= ma Quiescent Current I Q (Note 8) No-Load OpAmp ma Standby Quiescent Current Istby ON /OFF Pin=5 No-Load OpAmp ma ua Note 5: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. Note 6: Output pin sourcing current, No diode, inductor or capacitor connected to output. Note 7: Feedback pin removed from output and connected to 0. Note 8: Feedback pin removed from output and connected to +12 for the Adjustable, 3.3 and 5, versions, and +25 for the 12 and 15 versions, to force the output transistor OFF. Note 9: IN = 40. Note 10: The oscillator frequency reduces to approximately 11kHz in the event of an output short or an overload, which causes the regulated output voltage to drop approximately 40% from the nominal output voltage. This self-protection feature lowers the average power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%. Note 11: When oltage of OP pin > OP H, the circuit is OFF. When oltage of OP pin decrease less than OP L, the circuit is ON. Note 12: R L between FB and GND. Note 13: Good use of the PC board s ground plane can help considerably to dissipate heat. The exposed pad on the bottom of the IC package must be soldered to a ground plane and that plane should extend out from beneath the IC to help dissipate the heat. 6

7 PACKAGE OUTLINE DIMENSIONS Note : Information provided by IAT is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an IAT product; nor for any infringement of patents or other rights of third parties that may result from its use. We reserve the right to change the circuitry and specifications without notice. Life Support Policy: IAT does not authorize any IAT product for use in life support devices and/or systems. Life support devices or systems are devices or systems which, (I) are intended for surgical implant into the body or (II) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. Typical numbers are at 25 C and represent the most likely norm. 7