AAT1121 AAT, AAT1121 Datasheet

Page 1

... AAT1121 the ideal choice for portable applications. The AAT1121 delivers 250mA of load current, while maintaining a low 30µA no load quiescent current. The 1.5MHz switching frequency minimizes the size of external components, while keeping switching losses low ...

Page 2

... Input power return pin; connected to the source of the N-channel MOSFET. Connect to the output and input capacitor return. EP Exposed paddle (bottom): connect to ground directly beneath the package. Pin Configuration 2 1.5MHz, 250mA Step-Down Converter TDFN22-8/STDFN22-8 (Top View) VP PGND 1 8 VIN GND N AAT1121 1121.2007.03.1.2 ...

Page 3

... Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi- tions 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. 1121.2007.03.1.2 1.5MHz, 250mA Step-Down Converter 1 2 AAT1121 Value Units 6 0.3 ...

Page 4

... Enable Threshold High EN(H) I Input Low Current EN 1. The AAT1121 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. Output voltage tolerance is independent of feedback resistor network accuracy 1.5MHz, 250mA Step-Down Converter ...

Page 5

... Step-Down Converter 1.0 0.5 0.0 -0.5 -1.0 100 1000 0.1 1.0 0 3. 4.2V IN -1.0 0.1 100 1000 1.0 0.5 0.0 -0.5 -1.0 100 1000 0.1 AAT1121 DC Load Regulation (V = 1.2V 1.5µH) OUT 100 Output Current (mA) DC Load Regulation (V = 1.8V 3.3µH) OUT = 2. 100 Output Current (mA) DC Load Regulation (V = 3.0V 4.7µH) OUT = 4. 3.6V ...

Page 6

... No Load Quiescent Current vs. Input Voltage 85°C 35 25° -40° 4.7 5.1 5.5 2.7 AAT1121 Line Regulation (V = 1.8V) OUT I = 0mA OUT I = 50mA OUT I = 150mA OUT I = 10mA OUT I = 250mA OUT 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Switching Frequency Variation vs. Temperature (V = 3.6V 1.8V) IN OUT - ...

Page 7

... V OUT 2.0 1.9 1.8 1.7 250mA 1.6 10mA 0.2 0.0 -0.2 = 100pF) 5.0 4.5 4.0 3.5 3.0 AAT1121 N-Channel R vs. Input Voltage DS(ON) 120°C 100°C 85°C 25°C 3.0 3.5 4.0 4.5 5.0 Input Voltage (V) Load Transient Response = 3.6V 1.8V 4.7µF) IN OUT OUT V O 250mA I O 10mA I LX Time (25µs/div) 5 ...

Page 8

... Typical Characteristics Output Ripple (V = 3.6V 1.8V OUT OUT - Time (2µs/div) 8 1.5MHz, 250mA Step-Down Converter = 1mA 0.04 -20 0.03 0.02 0.01 0.00 -0.01 AAT1121 Output Ripple (V = 3.6V 1.8V 250mA) IN OUT OUT Time (200ns/div) 1121.2007.03.1.2 0.3 0.2 0.1 0.0 ...

Page 9

... Voltage Reference EN INPUT Functional Description The AAT1121 is a high performance 250mA, 1.5MHz monolithic step-down converter designed to operate with an input voltage range of 2.7V to 5.5V. The converter operates at 1.5MHz, which minimizes the size of external components. Typical values are 3.3µH for the output inductor and 4.7µF for the ceramic output capacitor ...

Page 10

... A In this case, a standard 4.7µH value is selected. For most designs, the AAT1121 operates with an inductor value of 1µH to 4.7µH. Table 1 displays inductor values for the AAT1121 with different output voltage options. Manufacturer's specifications list both the inductor DC current rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation characteristics ...

Page 11

... The input capacitor provides a low impedance loop . The calculated for the edges of pulsed current drawn by the AAT1121. Low ESR/ESL X7R and X5R ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as closely as possible to the IC. This keeps the high frequency content of the input current localized, minimizing EMI and input voltage ripple ...

Page 12

... With enhanced transient response for extreme pulsed load application, an external feed-forward estimated by: capacitor, (C3 in Figure 1), can be added OUT 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.8 1.85 2.0 2.5 3.3 Table 2: Adjustable Resistor Values For AAT1121 1 V · OUT IN(MAX) OUT = · L · F · · 3 IN(MAX) V 3.3V ⎞ ⎛ ⎞ OUT -1 · · ...

Page 13

... Thermal Calculations There are three types of losses associated with the AAT1121 step-down converter: switching loss- es, conduction losses, and quiescent current loss- es. Conduction losses are associated with the R characteristics of the power output switch- DS(ON) ing devices. Switching losses are dominated by the gate charge of the power output switching devices ...

Page 14

... Layout The suggested PCB layout for the AAT1121 is shown in Figures 2, 3, and 4. The following guide- lines should be used to help ensure a proper layout. 1. The input capacitor (C1) should connect as closely as possible to VP (Pin 1), PGND (Pin 8), and GND (Pin and L1 should be connected as closely as possible ...

Page 15

... I = 5mΩ · (66mA esr RMS 1121.2007.03.1.2 1.5MHz, 250mA Step-Down Converter = 200mA LOAD ⋅ 1.8V = 3µH (use 3.0µH; see Table 1) ⎛ ⎞ 1.8V ⋅ 228mA ⎝ ⎠ 4.2V = 4µF (use 4.7µF) 1 1.8V · (4.2V - 1.8V) · = 66mArms = 3.0µH · 1.5MHz · 4.2V 2 · 21.8µW AAT1121 15 ...

Page 16

... ESR · 4 · ⎝ I ⎠ ⎝ 0. 0.1Arms RMS esr · 5mΩ · (0.1A 0.05mW RMS AAT1121 Losses I 2 · (R · DSON(HS) O DSON(LS TOTAL · F · · 0.2 2 · (0.59 Ω · 1.8V + 0.42Ω · [4.2V - 1.8V ...

Page 17

... AAT1121 1 L1 (µH) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2.2 2.7 3.0/3.3 3.0/3.3 3.0/3.3 3.9/4.2 5.6 DCR Size (mm) (mΩ) LxWxH Type 88 3.0x3.0x1.0 Shielded 115 3.0x3.0x1.0 Shielded 135 3.0x3.0x1.0 Shielded 150 3.0x3.0x1.0 Shielded 180 3.0x3.0x1.0 Shielded 230 3 ...

Page 18

... Manufacturer Part Number Murata GRM118R60J475KE19B Murata GRM188R60J106ME47D 18 1.5MHz, 250mA Step-Down Converter Value (µF) 4.7 10 Table 5: Surface Mount Capacitors. AAT1121 Voltage Temp. Case Rating Co. Size 6.3 X5R 0603 6.3 X5R 0603 1121.2007.03.1.2 ...

Page 19

... Step-Down Converter Package Marking 1 TDFN22-8 RWXYY RWXYY TDFN22-8 0.600 ± 0.050 Detail "A" Bottom View AAT1121 Part Number (Tape and Reel) AAT1121IPS-0.6-T1 AAT1121IES-0.6-T1 0.350 ± 0.100 0.1 REF (optional) C0.3 Pin 1 Indicator (optional) Detail "A" ...

Page 20

... 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 20 1.5MHz, 250mA Step-Down Converter STDFN22-8 Detail "A" 0.80 ± 0.05 Bottom View 0.35 ± 0.05 Pin 1 Indicator (optional) Detail "A" AAT1121 1121.2007.03.1.2 ...