DATA SHEET AAT1232 24V, 100mA Step-Up Converter General Description Features The AAT1232 is a high frequency, high efficiency boost converter capable of 24V maximum output voltage. The internal power switch can deliver 100mA load current. It is the ideal power solution to power OLED, LCD, and CCD applications operating from a single cell lithium-ion battery. • • • • • The high switching frequency (up to 2MHz) provides fast response to load transients with small external components. The fully integrated control IC simplifies the design while reducing the total PCB footprint. The AAT1232 offers a true load disconnect feature which isolates the load from the power source when EN/SET is pulled low. This eliminates leakage current and maintains zero voltage at the output while disabled. The output voltage can be dynamically set by activating one of two reference levels (FB1 or FB2) through the SEL logic pin. Optionally, Skyworks' Simple Serial Control™ (S2Cwire™) interface provides dynamic programmability across a wide output voltage range through the EN/SET pin. The AAT1232 is available in a Pb-free, thermally-enhanced 16-pin 3x4mm TDFN low-profile package or a Pb-free 12-pin TSOPJW package. • • • • • • • • • • VIN Range: 2.7V to 5.5V Maximum Output: 24V @ 100mA True Load Disconnect Dynamic Voltage Control Options Hysteretic Control ▪ No External Compensation Components ▪ Excellent Load Transient Response ▪ High Efficiency at Light Load Up to 2MHz Switching Frequency Ultra-Small Inductor and Capacitors Integrated Low RDS(ON) MOSFET Switches Up to 85% Efficiency <1μA Shutdown Current Integrated Soft Start Cycle-by-Cycle Current Limit Short-Circuit, Over-Temperature Protection Available in TSOPJW-12 or TDFN34-16 Package -40°C to +85°C Temperature Range Applications • • • • • • • CCD Bias Circuit Digital Still Cameras LCD Bias Circuit Mobile Handsets MP3 Players OLED Displays PDAs and Notebook PCs Typical Application L1 2.2μH Input: 2.7V~5.5V C1 2.2μF VP VIN D1 Schottky 24V @ 100mA LIN AAT1232 R1 576kΩ C2 2.2μF, 25V SW FB1 PGND R2 10.0kΩ EN/SET FB2 SEL GND R3 20.0kΩ Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 1 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Pin Descriptions Pin # TSOPJW-12 TDFN34-16 Symbol 1 15, 16 VP 2 14 EN/SET 3 13 SEL 4 5 12 11 VIN N/C 6, 7 9, 10 SW 8 6, 7, 8 PGND 9 5 GND 10 4 FB2 11 3 FB1 12 1, 2 LIN N/A EP Function Input power pin; connected to the source of the P-channel MOSFET. Connect a 2.2μF or larger capacitor from these pins to PGND. IC active high enable pin. Alternative input pin for S2Cwire control utilizing FB2 reference. Logic high selects FB1 high output reference; logic low selects FB2 low output reference. Pull low for S2Cwire control. See Tables 1 and 2. Input voltage for the converter. Connect this pin directly to the VP pin. No connection. Do not make any connection to this pin. Boost converter switching node. Connect the power inductor between the SW pin and the LIN pin. Power ground for the boost converter; connected to the source of the internal N-channel MOSFET. Connect input and output capacitor returns to PGND. Ground pin. Feedback pin for low output voltage set point. Pin set to 0.6V when SEL is low and disabled when SEL is high. Voltage is set from 0.6V to 1.2V using S2Cwire control. Feedback pin for high output voltage set point. Pin set to 1.2V when SEL is high and disabled when SEL is low. Disabled with S2Cwire control. Switched power input. Connected to the power inductor. Exposed paddle (bottom). Internally connected to SW. May be externally connected to SW pins or left floating. Do not connect to GND or PGND. Pin Configuration TSOPJW-12 (Top View) VP EN/SET SEL VIN N/C SW 2 1 12 2 11 3 10 4 9 5 8 6 7 TDFN34-16 (Top View) LIN FB1 FB2 GND PGND SW LIN LIN FB1 FB2 GND PGND PGND PGND 1 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 VP VP EN/SET SEL VIN N/C SW SW Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Absolute Maximum Ratings1 TA = 25°C, unless otherwise noted. Symbol Description Value Units VIN, VP SW LIN, EN/SET, SEL, FB1, FB2 TJ TS TLEAD Input Voltage Switching Node -0.3 to 6.0 28 V V VIN + 0.3 V -40 to 150 -65 to 150 300 °C °C °C Value Units Maximum Rating Operating Temperature Range Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec) Recommended Operating Conditions Symbol Description JA Thermal Resistance PD Maximum Power Dissipation (TA = 25°C) TDFN34-16 TSOPJW-12 TDFN34-16 TSOPJW-12 44 160 2270 625 °C/W mW 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. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 3 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Electrical Characteristics1 TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C, VIN = 3.6V. Symbol Description Conditions Min Power Supply VIN Input Voltage Range VOUT(MAX) Maximum Output Voltage 2.7 VLOADREG VLINEREG/ VIN RDS(ON)L RDS(ON)IN Load Regulation VIN Rising Hysteresis VIN Falling SEL = GND, VOUT = 18V, IOUT = 0, R3 = 20k2, Switching SEL = GND, FB2 = 1.5V, Not Switching EN/SET = GND 2.7V < VIN < 5.5V, VOUT = 24V IOUT = 0 to 100mA, VIN = 2.7V to 5.0V, SEL = High IOUT = 0 to 100mA, VIN = 2.7V to 5.0V, SEL = Low IOUT = 0 to 100mA, R3 = 20k3 Line Regulation VIN = 2.7V to 5.5V, R3 = 20k TSS Soft-Start Time VUVLO IQ UVLO Threshold Quiescent Current ISHDN IOUT VIN Pin Shutdown Current Output Current FB1 FB1 Reference Voltage FB2 FB2 Reference Voltage 2.7V 5.5V 2.7V 5.5V 5.5 24 2.7 V V V mV V 0.3 40 mA 70 1.0 100 μA mA μA 1.164 1.2 1.236 V 0.582 0.6 0.618 V 3 VIN = 3.6V = = = = Units 150 From Enable to Output Regulation; VOUT = 15V VIN VIN VIN VIN Max 1.8 Low Side Switch On Resistance Input Disconnect Switch On Resistance TSD Over-Temperature Shutdown Threshold THYS Shutdown Hysteresis ILIM N-Channel Current Limit SEL, EN/SET SEL Threshold Low VSEL(L) VSEL(H) SEL Threshold High VEN/SET(L) Enable Threshold Low VEN/SET(H) Enable Threshold High TEN/SET LO EN/SET Low Time TEN/SET HI MIN Minimum EN/SET High Time TEN/SET HI MAX Maximum EN/SET High Time TOFF EN/SET Off Timeout TLAT EN/SET Latch Timeout IEN/SET EN/SET Input Leakage Typ 0.02 %/mA 0.6 %/V 0.08 0.18 0.35 ms 140 15 3.0 °C °C A 0.4 1.4 0.4 1.4 0.3 75 50 -1 75 500 500 1 V V V V μs ns μs μs μs μA 1. The AAT1232 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. Switching input current will vary with R1, R2, R3 resistor values. 3. Some improvement in line and load regulation is possible with smaller resistor values. 4 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Typical Characteristics Efficiency vs. Output Current Output Error vs. Output Current (VOUT = 18V; R3 = 20kΩ Ω) 90 70 VIN = 3.6V VIN = 4.2V 60 Output Error (%) VIN = 5V 80 Efficiency (%) (VOUT = 18V; R3 = 20kΩ Ω) 1.5 50 40 30 VIN = 5V 1.0 0.5 VIN = 4.2V 0.0 VIN = 3.6V -0.5 VIN = 2.7V -1.0 -1.5 20 0.1 1 10 0.1 100 Output Current (mA) 1.5 Output Error (%) Efficiency (%) (VOUT = 20V; R3 = 20kΩ Ω) VIN = 5V 70 VIN = 3.6V VIN = 4.2V 60 50 40 30 1 10 VIN = 5V 1.0 0.5 VIN = 4.2V 0.0 VIN = 3.6V -0.5 VIN = 2.7V -1.0 -1.5 20 0.1 100 0.1 Output Current (mA) Output Error (%) Efficiency (%) 1.5 70 VIN = 3.6V VIN = 4.2V 100 (VOUT = 24V; R3 = 20kΩ Ω) VIN = 5V 60 10 Output Error vs. Output Current (VOUT = 24V; R3 = 20kΩ) 80 1 Output Current (mA) Efficiency vs. Output Current 90 100 Output Error vs. Output Current (VOUT = 20V; R3 = 20kΩ Ω) 80 10 Output Current (mA) Efficiency vs. Output Current 90 1 50 40 30 VIN = 5V VIN = 4.2V 1.0 0.5 0.0 VIN = 3.6V -0.5 VIN = 2.7V -1.0 -1.5 20 0.1 1 10 Output Current (mA) 100 0.1 1 10 100 Output Current (mA) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 5 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Typical Characteristics Line Regulation Output Voltage Error vs. Temperature (VOUT = 18V; R3 = 20kΩ Ω) (VIN = 5V; VOUT = 18V; IOUT = 100mA) 0.2 2.5 2.0 0.1 Output Error (%) Accuracy (%) 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 0.0 -0.1 -0.2 -0.3 -0.4 -2.0 -2.5 2.5 3 3.5 4 4.5 5 5.5 -0.5 -40 6 -15 No Load Quiescent Current vs. Input Voltage 1.1 Supply Current (mA) Supply Current (mA) 0.4 0.36 0.32 0.28 0.24 0.2 0.16 0.12 0.08 4 4.5 5 5.5 0.9 0.8 0.6 0.5 0.3 0.2 0.0 -40 10 35 Output Ripple Output Ripple (VIN = 4.2V; VOUT = 18V; IOUT = 100mA) (VIN = 4.2V; VOUT = 18V; No Load) 60 85 18.2 1.0 18.0 4.0 18.0 0.8 17.8 3.0 17.8 0.6 17.6 2.0 17.6 0.4 17.4 1.0 17.4 0.2 17.2 0.0 17.2 0.0 -1.0 17.0 Time (500ns/div) Output Voltage (top) (V) 5.0 -0.2 17.0 Time (100µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 Inductor Current (bottom) (A) 18.2 Inductor Current (bottom) (A) Output Voltage (top) (V) -15 Temperature (°°C) Input Voltage (V) 6 85 (VIN = 3.6V; VOUT = 18V) 1.2 3.5 60 No Load Input Current vs. Temperature (VOUT = 18V; EN_High) 3 35 Temperature (°°C) Input Voltage (V) 2.5 10 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Load Transient Response Load Transient Response (VIN = 4.2V; IOUT = 20mA–60mA; VOUT = 18V) (VIN = 3.6V; IOUT = 20mA–60mA; VOUT = 12V) 18.05 1.2 18.00 0.9 17.95 0.6 17.90 0.3 17.85 0.0 17.80 -0.3 Output Voltage (V) (top) 1.5 12.10 1.50 12.05 1.20 12.00 0.90 11.95 0.60 11.90 0.30 11.85 0.00 -0.30 11.80 Time (200µs/div) Time (200µs/div) P-Channel RDS(ON) vs. Input Voltage N-Channel RDS(ON) vs. Input Voltage 160 300 280 140 120°C 260 100°C 240 RDS(ON) (mΩ) RDS(ON) (mΩ Ω) Inductor Current (A) (bottom) 18.10 Inductor Current (A) (bottom) Output Voltage (V) (top) Typical Characteristics 220 200 180 25°C 160 140 2.5 3 120°C 120 80 25°C 60 85°C 3.5 4 4.5 5 5.5 6 Input Voltage (V) 100°C 100 85°C 40 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage (V) Soft Start 16 2.8 12 2.4 8 2.0 4 1.6 0 1.2 -4 0.8 -8 0.4 -12 0.0 -16 -0.4 Input Current (bottom) (A) Enable Voltage (middle) (V) Output Voltage (top) (V) (VIN = 3.6V; CIN = 2.2µF; IOUT = 100mA; VOUT = 12V) Time (200µs/div) Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 7 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Functional Block Diagram VIN LIN VP Output Timer EN/SET SW Control FB1 1.2V VREF Output Select FB2 SEL GND Functional Description The AAT1232 consists of a DC/DC boost controller, an integrated slew rate controlled input disconnect MOSFET switch, and a MOSFET power switch. A high voltage rectifier, power inductor, output capacitor, and resistor divider network are required to implement a DC/DC boost converter. Control Loop The AAT1232 provides the benefits of current mode control with a simple hysteretic feedback loop. The device maintains exceptional DC regulation, transient response, and cycle-by-cycle current limit without additional compensation components. 8 PGND The AAT1232 modulates the power MOSFET switching current in response to changes in output voltage. This allows the voltage loop to directly program the required inductor current in response to changes in the output load. The switching cycle initiates when the N-channel MOSFET is turned ON and current ramps up in the inductor. The ON interval is terminated when the inductor current reaches the programmed peak current level. During the OFF interval, the input current decays until the lower threshold, or zero inductor current, is reached. The lower current is equal to the peak current minus a preset hysteresis threshold which determines the inductor ripple current. The peak current is adjusted by the controller until the output current requirement is met. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter The magnitude of the feedback error signal determines the average input current. Therefore, the AAT1232 controller implements a programmed current source connected to the output capacitor and load resistor. There is no right-half plane zero, and loop stability is easily achieved with no additional compensation components. Increased load current results in a drop in the output feedback voltage (FB1 or FB2) sensed through the feedback resistors (R1, R2, R3). The controller responds by increasing the peak inductor current, resulting in higher average current in the inductor. Alternatively, decreased output load results in an increase in the output feedback voltage (FB1 or FB2 pin). The controller responds by decreasing the peak inductor current, resulting in lower average current in the inductor. At light load, the inductor OFF interval current goes below zero and the boost converter enters discontinuous mode operation. Further reduction in the load results in a corresponding reduction in the switching frequency. AAT1232 pulsed frequency operation reduces switching losses and maintains high efficiency at light loads. Operating frequency varies with changes in the input voltage, output voltage, and inductor size. Once the boost converter has reached continuous mode, further increases in the output load will not significantly increase the operating frequency. A small 2.2μH (±20%) inductor is selected to maintain high frequency switching (up to 2MHz) and high efficiency operation for outputs from 10V to 24V. Output Voltage Programming The output voltage may be programmed through a resistor divider network located from output capacitor to FB1/ FB2 pins to ground. Pulling the SEL pin high activates the FB1 pin which maintains a 1.2V reference voltage, while the FB2 reference is disabled. Pulling the SEL pin low activates the FB2 pin which maintains a 0.6V reference, while the FB1 reference is disabled. This function allows dynamic selection between two distinct output voltages across a 2X range (maximum). An additional resistor between FB1 and FB2 allows the designer to program the outputs across a reduced <2X range. Alternatively, the output voltage may be programmed to any of 16 voltage levels using the S2Cwire serial digital input. The single wire S2Cwire interface provides highspeed output voltage programmability across a 2X output voltage range. S2Cwire functionality is enabled by pulling the SEL pin low and providing S2Cwire input to the EN/SET pin. Table 2 details the FB2 reference voltage versus S2Cwire rising edges. Soft Start / Enable The input disconnect switch is activated when a valid input voltage is present and the EN/SET pin is pulled high. The slew rate control on the P-channel MOSFET ensures minimal inrush current as the output voltage is charged to the input voltage, prior to switching of the N-channel power MOSFET. Monotonic turn-on is guaranteed by the built-in soft-start circuitry. Soft-start eliminates output voltage overshoot across the full input voltage range and all loading conditions. Some applications may require the output to be active when a valid input voltage is present. In these cases, add a 10k resistor between the VIN, VP, and EN/SET pins to avoid startup issues. Current Limit and Over-Temperature Protection The switching of the N-channel MOSFET terminates when current limit of 3.0A (typical) is exceeded. This minimizes power dissipation and component stresses under overload and short-circuit conditions. Switching resumes when the current decays below the current limit. Thermal protection disables the AAT1232 when internal dissipation becomes excessive. Thermal protection disables both MOSFETs. The junction over-temperature threshold is 140°C with 15°C of temperature hysteresis. Once an over-temperature or over-current fault condition is removed, the output voltage automatically recovers. Under-Voltage Lockout Internal bias of all circuits is controlled via the VIN input. Under-voltage lockout (UVLO) guarantees sufficient VIN bias and proper operation of all internal circuitry prior to activation. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 9 DATA SHEET AAT1232 24V, 100mA Step-Up Converter R4 10k JP1 VIN 3 2 1 Enable JP2 3 2 1 C1 2.2μF 1 2 3 4 5 6 VP LIN EN/SET FB1 SEL FB2 VIN GND N/C PGND SW SW D1 Schottky L1 2.2μH U1 12 11 10 9 8 7 VOUT R1 576k C2 2.2μF R2 10k R3 20k Select U1 AAT1232 TSOPJW12 C1 10V 0805 2.2μF C2 25V 0805 2.2μF D1 30V 0.5A MBR0530T SOD-123 L1 2.2μH NR4018T2R2 R1 576k 0603 R2, R4 10k 0603 R3 20k 0603 R4 10k 0603 Figure 1: AAT1232 Demo Board Schematic. Application Information capacitors sized as small as 0603 are available which meet these requirements. Selecting DC/DC Boost Capacitors Large capacitance tantalum or solid-electrolytic capacitors may be necessary to meet stringent output ripple and transient load requirements. These can replace (or be used in parallel with) ceramic capacitors. Both tantalum and OSCON-type capacitors are suitable due to their low ESR and excellent temperature stability (although they exhibit much higher ESR than MLC capacitors). Aluminumelectrolytic types are less suitable due to their high ESR characteristics and temperature drift. Unlike MLC capacitors, these types are polarized and proper orientation on input and output pins is required. 30% to 70% voltage derating is recommended for tantalum capacitors. The high output ripple inherent in the boost converter necessitates low impedance output filtering. Multi-layer ceramic (MLC) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (ESR) and equivalent series inductance (ESL), and are well suited for use with the AAT1232 boost regulator. MLC capacitors of type X7R or X5R are recommended to ensure good capacitance stability over the full operating temperature range. The output capacitor is sized to maintain the output load without significant voltage droop during the power switch ON interval, when the output diode is not conducting. A ceramic output capacitor from 2.2μF to 4.7μF is recommended. Typically, 25V rated ceramic capacitors are required for the 24V boost output. Ceramic capacitors sized as small as 0805 are available which meet these requirements. MLC capacitors exhibit significant capacitance reduction with applied voltage. Output ripple measurements should confirm that output voltage droop is acceptable. The boost converter input current flows during both ON and OFF switching intervals. The input ripple current is less than the output ripple and, as a result, less input capacitance is required. A ceramic output capacitor from 1μF to 3.3μF is recommended. Minimum 6.3V rated ceramic capacitors are required at the input. Ceramic 10 Selecting the Output Diode To ensure minimum forward voltage drop and no recovery, high voltage Schottky diodes are considered the best choice for the AAT1232 boost converter. The AAT1232 output diode is sized to maintain acceptable efficiency and reasonable operating junction temperature under full load operating conditions. Forward voltage (VF) and package thermal resistance (JA) are the dominant factors to consider in selecting a diode. The diode’s published current rating may not reflect actual operating conditions and should be used only as a comparative measure between similarly rated devices. 20V rated Schottky diodes are recommended for outputs less than 15V, while 30V rated Schottky diodes are recommended for outputs greater than 15V. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter The average diode current is equal to the output current. IAVG = IOUT The average output current multiplied by the forward diode voltage determines the loss of the output diode. PLOSS_DIODE = IAVG · VF = IOUT · VF Diode junction temperature can be estimated. TJ = TAMB + ΘJA · PLOSS_DIODE The junction temperature should be maintained below 110ºC, but may vary depending on application and/or system guidelines. The diode JA can be minimized with additional PCB area on the cathode. PCB heatsinking the anode may degrade EMI performance. The reverse leakage current of the rectifier must be considered to maintain low quiescent (input) current and high efficiency under light load. The rectifier reverse current increases dramatically at high temperatures. The maximum duty cycle can be estimated from the relationship for a continuous mode boost converter. Maximum duty cycle (DMAX) is the duty cycle at minimum input voltage (VIN(MIN)): DMAX = Where VF is the Schottky diode forward voltage and can be estimated at 0.5V. Manufacturer’s specifications list both the inductor DC current rating, which is a thermal limitation, and peak inductor current rating, which is determined by the saturation characteristics. Measurements at full load and high ambient temperature should be completed to ensure that the inductor does not saturate or exhibit excessive temperature rise. The output inductor (L) is selected to avoid saturation at minimum input voltage, maximum output load conditions. Peak current may be calculated from the following equation, again assuming continuous conduction mode. Worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. Switching frequency can be estimated at 500kHz with a 2.2μH inductor. Selecting the Boost Inductor The AAT1232 controller utilizes hysteretic control and the switching frequency varies with output load and input voltage. The value of the inductor determines the maximum switching frequency of the AAT1232 boost converter. Increased output inductance decreases the switching frequency, resulting in higher peak currents and increased output voltage ripple. To maintain 2MHz maximum switching frequency, an output inductor sized from 1.5μH to 2.7μH is recommended. The switching period is divided between ON and OFF time intervals. 1 = TON + TOFF FS The ON time is the period which the N-channel power MOSFET is conducting and storing energy in the boost inductor. Duty cycle is defined as the ON time divided by the total switching interval. D= TON TON + TOFF (VOUT + VF - VIN(MIN)) (VOUT + VF) IPEAK = IOUT D · VIN(MIN) + MAX (1 - DMAX) (2 · FS · L) The RMS current flowing through the boost inductor is equal to the DC plus AC ripple components. Under worstcase RMS conditions, the current waveform is critically continuous. The resulting RMS calculation yields worstcase inductor loss. The RMS value should be compared against the manufacturer’s temperature rise, or thermal derating, guidelines. IRMS = IPEAK 3 For a given inductor type, smaller inductor size leads to an increase in DCR winding resistance and, in most cases, increased thermal impedance. Winding resistance degrades boost converter efficiency and increases the inductor operating temperature. PLOSS_INDUCTOR = IRMS2 · DCR = TON ⋅ FS Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 11 DATA SHEET AAT1232 24V, 100mA Step-Up Converter To ensure high reliability, the inductor temperature should not exceed 100°C. Manufacturer’s recommendations should be consulted. In some cases, PCB heatsinking applied to the AAT1232 LIN node (non-switching) can improve the inductor’s thermal capability. PCB heatsinking may degrade EMI performance when applied to the SW node (switching) of the AAT1232. Shielded inductors provide decreased EMI and may be required in noise sensitive applications. Unshielded chip inductors provide significant space savings at a reduced cost compared to shielded (wound and gapped) inductors. Chip-type inductors have increased winding resistance when compared to shielded, wound varieties. Setting the Output Voltage The output voltage may be programmed through a resistor divider network located from the output to FB1 and FB2 pins to ground. Pulling the SEL pin high activates the FB1 pin which maintains a 1.2V reference voltage, while the FB2 reference is disabled. Pulling the SEL pin low activates the FB2 pin which maintains a 0.6V reference, while the FB1 reference is disabled. The AAT1232 output voltage can be programmed by one of three methods. First, the output voltage can be static by pulling the SEL logic pin either high or low. Second, the output voltage can be dynamically adjusted between two pre-set levels within a 2X operating range by toggling the SEL logic pin. Third, the output can be dynamically adjusted to any of 16 preset levels within a 2X operating range using the integrated S2Cwire single wire interface via the EN/SET pin. Option 1: Static Output Voltage A static output voltage can be configured by pulling the SEL either high or low. SEL pin high activates the FB1 reference pin to 1.2V (nominal). Alternatively, the SEL pin is pulled low to activate the FB2 reference at 0.6V (nominal). Table 1 provides details of resistor values for common output voltages from 10V to 24V for SEL = High and SEL = Low options. In the static configuration, the FB1 pin should be directly connected to FB2. The resistor between FB1 and FB2 pins is not required. Option 2: Dynamic Voltage Control Using SEL Pin The output may be dynamically adjusted between two output voltages by toggling the SEL logic pin. Output voltages VOUT(1) and VOUT(2) correspond to the two output 12 references, FB1 and FB2. Pulling the SEL logic pin high activates VOUT(1), while pulling the SEL logic pin low activates VOUT(2). The minimum output voltage must be greater than the specified maximum input voltage plus margin to maintain proper operation of the AAT1232 boost converter. In addition, the ratio of output voltages VOUT(2)/VOUT(1) is always less than 2.0, corresponding to a 2X (maximum) programmable range. Table 1 is provided to allow programming of common output voltages using Option 1 or 2. The feedback references FB1 and FB2 are enabled or disabled using the SEL logic pin, corresponding to VOUT(1) and VOUT(2). Option 3: Dynamic Voltage Control Using S2Cwire Interface The output can be dynamically adjusted by the host controller to any of 16 pre-set output voltage levels using the integrated S2Cwire interface. The EN/SET pin serves as the S2Cwire interface input. The SEL pin must be pulled low when using the S2Cwire interface. S2Cwire Serial Interface Skyworks' S2Cwire serial interface is a proprietary highspeed single-wire interface available only from Skyworks. The S2Cwire interface records rising edges of the EN/SET input and decodes into 16 different states. Each state corresponds to a voltage setting on the FB2 pin. S2Cwire Serial Interface Timing The S2Cwire serial interface has flexible timing. Data can be clocked-in at speeds up to 1MHz. After data has been submitted, EN/SET is held high to latch the data for a period TLAT. The output is subsequently changed to the predetermined voltage. When EN/SET is set low for a time greater than TOFF, the AAT1232 is disabled. When disabled, the register is reset to the default value, which sets the FB2 pin to 0.6V if EN is subsequently pulled high. S2Cwire Output Voltage Programming The AAT1232 is programmed through the S2Cwire interface according to Table 2. The rising clock edges received through the EN/SET pin determine the feedback reference and output voltage set-point. Upon power up with the SEL pin low and prior to S2Cwire programming, the default feedback reference voltage is set to 0.6V. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter R3 = 4.99kΩ R3 = 20.0kΩ VOUT (SEL = High) VOUT (SEL = Low) R1 (kΩ) R2 (kΩ) R1 (kΩ) R2 (kΩ) 10.0 12.0 15.0 16.0 18.0 20.0 24.0 12.0 15.0 16.0 18.0 15.0 16.0 18.0 18.0 20.0 24.0 24.0 10.0 12.0 15.0 16.0 18.0 20.0 24.0 10.0 10.0 10.0 10.0 12.0 12.0 12.0 15.0 15.0 15.0 18.0 36.5 44.2 57.6 61.9 69.8 78.7 95.3 78.7 95.3 121 127 143 162 196 75.0 76.8 76.8 78.7 90.9 93.1 93.1 115 118 118 143 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3.32 1.65 1.24 0.562 3.01 2.49 1.65 3.32 2.49 1.24 2.49 147 182 232 249 280 316 383 316 383 487 511 590 649 787 301 309 309 316 374 374 374 464 475 475 576 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13.0 6.65 4.99 2.21 12.1 10.0 6.65 13.3 10.0 4.99 10.0 Table 1: SEL Pin Voltage Control Resistor Values (1% resistor tolerance). EN/SET Rising Edges FB2 Reference Voltage (V) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0.60 (Default) 0.64 0.68 0.72 0.76 0.80 0.84 0.88 0.92 0.96 1.00 1.04 1.08 1.12 1.16 1.20 Table 2: S2Cwire Voltage Control Settings (SEL = Low). Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 13 DATA SHEET AAT1232 24V, 100mA Step-Up Converter THI TLO TOFF T LAT EN/SET 1 2 Data Reg n-1 n ≤ 16 0 n 0 Figure 3: S2Cwire Timing Diagram to Program the Output Voltage. PCB Layout Guidelines Boost converter performance can be adversely affected by poor layout. Possible impact includes high input and output voltage ripple, poor EMI performance, and reduced operating efficiency. Every attempt should be made to optimize the layout in order to minimize parasitic PCB effects (stray resistance, capacitance, inductance) and EMI coupling from the high frequency SW node. 3. 4. 5. A suggested PCB layout for the AAT1232 boost converter is shown in Figures 4 and 5. The following PCB layout guidelines should be considered: 6. 1. 7. 2. Minimize the distance from capacitor C1 and C2 negative terminal to the PGND pins. This is especially true with output capacitor C2, which conducts high ripple current from the output diode back to the PGND pins. Place the feedback resistors close to the output terminals. Route the output pin directly to resistor R1 Figure 4: AAT1232 Evaluation Board Top Side Layout. 14 to maintain good output regulation. R3 should be routed close to the output GND pin. Minimize the distance between L1 to D1 and switching pin SW; minimize the size of the PCB area connected to the SW pin. Maintain a ground plane and connect to the IC RTN pin(s) as well as the GND terminals of C1 and C2. Consider additional PCB area on D1 cathode to maximize heatsinking capability. This may be necessary when using a diode with a high thermal resistance. When using the TDFN34-16 package, connect paddle to SW pin or leave floating. Do not connect to RTN/ GND conductors. To avoid problems at startup, add a 10k resistor between the VIN, VP and EN/SET pins (R4). This is critical in applications requiring immunity from input noise during “hot plug” events, e.g. when plugged into an active USB port. Figure 5: AAT1232 Evaluation Board Bottom Side Layout. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Manufacturer Part Number Rated IF(AV) Current (A)1 Rated Voltage (V) Thermal Resistance (ΘJA, °C/W)1 Case Diodes, Inc. Diodes, Inc. Diodes, Inc. Diodes, Inc. ON Semi ON Semi Zetex Zetex B340LA SD103AWS BAT42WS B0520WS MBR130LSFT MBR0530T ZHCS350 BAT54 3.00 0.35 0.20 0.50 1.00 0.50 0.35 0.20 40 30 30 20 30 30 40 30 25 625 625 426 325 206 330 330 SMA SOD-323 SOD-323 SOD-323 SOD-123 SOD-123 SOD-523 SOT-23 Table 3: Typical Surface Mount Schottky Rectifiers for Various Output Loads (select TJ < 110°C in application circuit). Manufacturer Part Number Inductance (μH) Max DC ISAT Current (A) DCR (Ω) Size (mm) LxWxH Type Sumida Sumida Sumida Murata Murata Taiyo Yuden Taiyo Yuden Coiltronics Coiltronics Coiltronics CDRH4D22/HP-2R2 CDR4D11/HP-2R4 CDRH4D18-2R2 LQH662N2R2M03 LQH55DN2R2M03 NR4018T2R2 NR3015T2R2 SD3814-2R2 SD3114-2R2 SD3112-2R2 2.2 2.4 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.50 1.70 1.32 3.30 3.20 2.70 1.48 1.90 1.48 1.12 35 105 75 19 29 60 60 77 86 140 5.0x5.0x2.4 4.8x4.8x1.2 5.0x5.0x2.0 6.3x6.3x4.7 5.0x5.7x4.7 4.0x4.0x1.8 3.0x3.0x1.5 3.8x3.8x1.4 3.1x3.1x1.4 3.1x3.1x1.2 Shielded Shielded Shielded Shielded Non-Shielded Shielded Shielded Shielded Shielded Shielded Table 4: Typical Surface Mount Inductors for Various Output Loads (select IPEAK < ISAT). Manufacturer Part Number Type Value (μF) Voltage (V) Temp. Co. Footprint LxWxH (mm) Murata Murata Murata Murata Murata GRM188R60J475KE19D GRM188R61A225KE34D GRM188R61C225KA88 GRM21BR61E225KA12L GRM188R61E105KA12D Ceramic Ceramic Ceramic Ceramic Ceramic 2.2 2.2 2.2 2.2 1.0 6.3 10 16 25 25 X5R X5R X5R X5R X5R 0603 0603 0805 0805 0603 Table 5: Typical Surface Mount Capacitors for Various Output Loads. 1. Results may vary depending on test method used and specific manufacturer. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 15 DATA SHEET AAT1232 24V, 100mA Step-Up Converter Ordering Information Package Marking1 Part Number (Tape and Reel)2 TSOPJW-12 TDFN34-16 SXXYY SXXYY AAT1232ITP-T1 AAT1232IRN-T1 Skyworks Green™ products are compliant with all applicable legislation and are halogen-free. For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074. Package Information3 TSOPJW-12 2.85 ± 0.20 2.40 ± 0.10 0.20 + 0.10 - 0.05 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 7° NOM 0.04 REF 0.055 ± 0.045 0.15 ± 0.05 + 0.10 1.00 - 0.065 0.9625 ± 0.0375 3.00 ± 0.10 4° ± 4° 0.45 ± 0.15 0.010 2.75 ± 0.25 All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. 16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 DATA SHEET AAT1232 24V, 100mA Step-Up Converter TDFN34-16 3.000 ± 0.050 1.600 ± 0.050 Detail "A" 3.300 ± 0.050 4.000 ± 0.050 Index Area 0.350 ± 0.100 Top View 0.230 ± 0.050 Bottom View C0.3 (4x) 0.050 ± 0.050 0.450 ± 0.050 0.850 MAX Pin 1 Indicator (optional) 0.229 ± 0.051 Side View Detail "A" All dimensions in millimeters. Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes. No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. 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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012 17