Advanced Analog Technology, Inc. AAT1102 Product information presented is current as of publication date. Details are subject to change without notice ADVANCED PWM DC-DC CONVERTER WITH INTERNAL SWITCH AND SOFT-START FEATURES GENERAL DESCRIPTION High Efficiency: 90% Adjustable Output: VDD to 12.5V Adjustable Frequency: 640kHz or 1.3MHz The AAT1102 is a step-up DC-DC converter with a 1.6A, 0.23Ω internal switch. Equipped with an external compensation pin, this device offers user flexibility in determining loop dynamic and adjusting operating frequency. AAT1102 also allows the use of small, low equivalent resistance (ESR) ceramic output capacitor, and it’s capable of converting a standard input of 3.3V to multiple outputs of 8V, − 8V , and 23V. Furthermore, filtering and loop performance are facilitated and enhanced by a high switching frequency of either 640 kHz or1.3MHz. 1.6A, 0.23Ω, Internal Switch Wide Input Range: +2.6V to +5.5V Low Shutdown Current: 0.1µA Programmable Soft-Start Small 8-Pin MSOP Package PIN CONFIGURATION TOP VIEW EO 1 8 IN 2 7 FREQ 6 VDD SS AAT1102 SHDN GND 3 4 5 8-Pin MSOP – SW The AAT1102’s versatility comes with a power-smart design. A soft-start programmed with an external capacitor that sets the input current ramp rate, reduces the current consumption to 0.1µA in shutdown mode. When operating, a mere 2.6V input yields an impressive output voltage as high as 12.5V. High switching frequency and economical design allow AAT1102 to be less than 1.1mm high. Its compact 8-pin MSOP package and superior performance make it an ideal part for biasing TFT displays. – – Advanced Analog Technology, Inc. – Page 1 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 PIN DESCRIPTIONS PIN NAME FUNCTION 1 EO Compensation Pin for Error Amplifier 2 IN Feedback Pin with a Typical Reference Voltage of 1.24V, VOUT = IN(1+ 3 4 5 6 SHDN GND SW VDD 7 FREQ 8 SS R1 ) R2 Shutdown Control Pin. The Device Will Turn Off When SHDN is Low Ground Switch Pin Power Supply Pin Frequency Select Pin. Switch Oscillator Frequency to 640kHz When FREQ is Low, and 1.3MHz When FREQ is High Soft-Start Control Pin. No Soft-Start When the Pin is Left Open ABSOLUTE MAXIMUM RATINGS PARAMETER SW to GND IN, SHDN, VDD , FREQ to GND SS, EO to GND SYMBOL VALUE − 0.3 to +18 UNIT V − 0.3 to +6 V − 0.3 V to ( VDD + 0.3V) V RMS SW Pin Current I SW 1.2 A Continuous Power Dissipation ( TC = + 70 ) 8-Pin MSOP (De-Rate 4.1 mW / above +70) Operation Temperature Range Pd 330 mW TC − 20 to +85 Tstorage − 45 to +125 TL +300 Storage Temperature Range Lead Temperature (Soldering for 10 seconds) Note: 1. Absolute Maximum Ratings are threshold limit values that must not be exceeded. 2. Operation above these absolute maximum ratings may cause degradation or permanent damage to the device. 3. These are stress ratings only and do not necessarily imply functional operation below these limits. – – – Advanced Analog Technology, Inc. – Page 2 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 ELECTRICAL CHARACTERISTICS VDD = SHDN = 3V , FREQ = GND, unless otherwise specified. Typical values are at TC = +25 o C ) PARAMETER Input Supply Voltage Range VDD Under Voltage Lockout SYMBOL CONDITIONS VDD UVLO Quiescent Current I DD Shutdown Current I SC MIN TYP 2.6 MAX UNITS 5.5 V V When VDD is rising, typical hysteresis is 40mV; SW 2.25 remains off below this level VIN = 1.3V, not switching 2.38 2.52 0.21 0.35 VIN = 1.0V, switching 1.2 5.0 SHDN = 0.1 10.0 GND mA µA ERROR AMPLIFIER PARAMETER SYMBOL Feedback Voltage VIN VDD Input Bias Current I IN Feedback-Voltage Line Regulation Transconductance Voltage Gain gm AV CONDITIONS MIN TYP MAX UNITS Level to produce VEO = 1.222 1.240 1.258 V 1.24V VIN= 1.24V 0 40 nA Level to produce VEO = 1.24V, 0.05 0.15 %/V 2.6V < VDD < 5.5V ∆I = 5 µA µA /V 70 105 240 V/V 1,500 OSCILLATOR PARAMETER Frequency Maximum Duty Cycle SYMBOL f OSC D MAX CONDITIONS FREQ = GND FREQ = VDD FREQ = GND FREQ = VDD MIN 540 1,100 79 TYP MAX UNITS 640 740 kHz 1,320 1,600 85 92 % 85 – – – Advanced Analog Technology, Inc. – Page 3 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 ELECTRICAL CHARACTERISTICS VDD = SHDN = 3V , FREQ = GND, unless otherwise specified. Typical values are at TC = +25o C ) N-CHANNEL SWITCH PARAMETER Current Limit On-Resistance SYMBOL CONDITIONS I LIM R ON VDD = 1V, Duty Cycle = 65% I SW = 1.2A I SWOFF Leakage Current MIN 1.2 VSW = 12V TYP MAX UNITS 1.6 2.3 A 0.23 0.50 Ω µA 0.01 20.00 TYP MAX UNITS SOFT-START PARAMETER SYMBOL Reset Switch Resistance Charge Current CONDITIONS VSS = 1.2V MIN Ω 1.5 4.0 300 7.0 MIN TYP MAX UNITS µA CONTROL INPUTS PARAMETER SYMBOL Input Low Voltage VIL Input High Voltage VIH Hysteresis CONDITIONS SHDN, FREQ; VDD = 2.6V to 5.5V SHDN, FREQ; VDD = 2.6V to 5.5V 0.3˙ VDD 0.7˙ VDD FREQ Pull-Down Current I FREQ SHDN Input Current I V 0.1˙ VDD SHDN, FREQ 1.8 SHDN V V 5.0 9.0 µA 0.001 1.000 µA – – – Advanced Analog Technology, Inc. – Page 4 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Typical Operating Characteristics S TEP - UP REG ULATOR OUTP UT V OLTAG E v s . LOAD CURRENT(V MAIN= 8 . 3 V ) LOAD CURRENT(mA) M AX IM UM IND UC TOR C UR R ENT(VMAIN= 8 . 3 V) v s . INPUT VOLTAGE INDUCTOR CURRENT(mA) INPUT VOLTAGE(V) – – – Advanced Analog Technology, Inc. – Page 5 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Fig. 1 TYPICAL APPLICATION CIRCUIT VDD 2.6V TO 5V ON/ OFF – – – Advanced Analog Technology, Inc. – Page 6 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Fig. 2 BLOCK DIAGRAM Σ – – – Advanced Analog Technology, Inc. – Page 7 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Fig. 3 AAT1102 IN A SEPIC CONFIGURATION VDD 2.6V TO 5V – – – Advanced Analog Technology, Inc. – Page 8 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Fig. 4 MULTIPLE-OUTPUT TFT LCD POWER SUPPLY – – – Advanced Analog Technology, Inc. – Page 9 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Inductor selection V D I L ( peak ) = I IN + IN , where D is duty cycle 2 Lf s I V And I IN = o , D = 1 − IN , 1− D Vo The inductor current rating must be greater than Power Stage Transfer Functions The duty to output voltage transfer function T p is: T p ( s) = vo ( s + w )(s − w z 2 ) = T p 0 2 esr 2 d s + 2ξwn s + wn I L(peak) . Where T p 0 = VO Loop Compensation Design And − rc 1 , wesr = (1 − D )(RL + rc ) Crc RL (1 − D ) − r , wn = L (1 − D )2 RL + r LC (RL + rc ) 2 C[r (R L + rc ) + R L rc (1 − D ) ] + L = , 2 2 LC (R L + rc )[r + (1 − D ) R L ] 2 wz 2 = ξ r = rL + DrDS + (1 − D ) R F rL is the inductor equivalent series resistance, rc is capacitor ESR, RL is the converter load resistance, C is output filter capacitor, rDS is the Fig.1. Closed-current loop for boost with PCM transistor on-resistance, and RF is the diode forward resistance. The duty to inductor current transfer function T pi is: T pi ( s ) = s + w zi il = T pi 0 2 2 d s + 2ξwn s + wn Where Tpi 0 = VO (RL + 2rc ) 1 , wzi = L(RL + rc ) C (RL / 2 + rc ) Fig.2. Block diagram of boost converter with PCM – – – Advanced Analog Technology, Inc. – Page 10 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 Current Sampling Transfer Function = β g m Rc Error voltage to duty transfer function Fm is: ( Where wsh = 2 s + w c 12 f s T p 0 × s R cs T pi 0 (s + wz1 )(s − wz 2 ) (s + wzi )( s 2 + sws h + 12 f s 2 ) ) 2 f s s 2 + 2ξwn s + wn d = Fm (s ) = v ei T pi 0 Rcs s (s + w zi )(s + wsh ) 2 2 Where β = 3ws 1 − α M − Ma , ,α = 2 π 1 + α M1 + M a ws = 2π . f s V FB , Vo The compensator transfer function Therefore, Fm depends on duty to inductor current T ( s ) = vc = g R s + wc , where w = 1 c m c c v fb s Rc C c transfer function T pi , and f s is the clock switching frequency; Rcs is the current-sense amplifier transresistance. For the boost converter M 1 = V IN / L and M 2 = ( VO - V IN )/ L For AAT1102 , Rcs = 0.275 V/A, M a is slope compensation, M a =0.8106. is: The closed-current loop transfer function Ticl Ticl ( s ) = ( ) 12 f s s 2 + 2ξwn s + wn × Rcs T pi 0 (s + w zi ) s 2 + wsh s + 12 f s 2 2 ( 2 ) Fig.3. Voltage loop compensator Compensator design guide: The Voltage-Loop Gain With Current Loop Closed 1. Crossover frequency f ci < 2. Gain margin>10dB The control to output voltage transfer function Td is: v ( s) Td ( s ) = o = Ticl ( s )T p ( s ) v c (s ) The voltage-loop gain with current loop closed is: 1 fs 2 3. Phase margin>40 4. The Lvi ( s ) = 1 at crossover frequency, Therefore, the compensator resistance, Rc is determined by: Lvi ( s ) = βTc ( s )Td ( s ) – – – Advanced Analog Technology, Inc. – Page 11 of 18 V4.0 Advanced Analog Technology, Inc. Rc = AAT1102 (RL + 2rc ) Vo 2πf ci CRcs VFB kg m r (1 − D )RL − (1 − D ) VFB is equal to reference voltage, VREF . VREF =1.24V, k is the correct factor, and k = (6 − 8) 5. The output filter capacitor is chosen so C . RL pole cancels Rc . C c zero Rc C c = C RL + rc , and (1 − 3) 2 C RL + rc (1 − 3)Rc 2 Example: V IN =5V, VO =9.6V, I O =250mA, f s =600 kHz, Cc = Fig.5. Bode diagram using Matlab simulation VFB =1.25V, L = 6.8uH , g m = 105uS , Rcs = 0.275 V/A, rL = 0.1Ω , rDS = 0.23Ω , rC = 50mΩ , k =7 RF = 1.4Ω , f ci = 21.4 kHz, C c =1.3nF, Rc = 27k , C =4.7uF Fig.4. CH1: PWM waveform, CH2, v p − p for Vo – – – Advanced Analog Technology, Inc. – Page 12 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 PACKAGE DIMENSION MSOP-8 – – – Advanced Analog Technology, Inc. – Page 13 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 PACKAGE DIMENSION (CONT.) MSOP-8 – – – Advanced Analog Technology, Inc. – Page 14 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 TAPE AND REEL PACKING METHOD: 2,500PCS/REEL, 1 REEL/BOX – – – Advanced Analog Technology, Inc. – Page 15 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 TAPE AND REEL (CONT.) PACKING METHOD: 2,500PCS/REEL, 1 REEL/BOX – – – Advanced Analog Technology, Inc. – Page 16 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 PART MARKING MSOP8 TOP MARKING 1102 MAAC MSOP8 BACK MARKING YYWW – – – Advanced Analog Technology, Inc. – Page 17 of 18 V4.0 Advanced Analog Technology, Inc. AAT1102 ORDERING INFORMATION – – – Advanced Analog Technology, Inc. – Page 18 of 18 V4.0