19-5481; Rev 5; 6/12 KIT ATION EVALU LE B A IL A AV 2.1MHz, High-Voltage, 600mA Mini-Buck Converter Features The MAX16904 is a small, synchronous buck converter with integrated high-side and low-side switches. The device is designed to deliver 600mA with input voltages from +3.5V to +28V while using only 25µA quiescent current at no load. Voltage quality can be monitored by observing the PGOOD signal. The MAX16904 can operate in dropout by running at 97% duty cycle, making it ideal for automotive and industrial applications. The MAX16904 operates at a 2.1MHz frequency, allowing for small external components and reduced output ripple. It guarantees no AM band interference. SYNC input programmability enables three frequency modes for optimized performance: forced fixed-frequency operation, SKIP mode (ultra-low quiescent current of 25µA), and synchronization to an external clock. The MAX16904 can be ordered with spread-spectrum frequency modulation, designed to minimize EMI-radiated emissions due to the modulation frequency. o Wide +3.5V to +28V Input Voltage Range o Tolerates Input Voltage Transients to +42V o 600mA Minimum Output Current with Overcurrent Protection o Fixed Output Voltages (+3.3V and +5V) o 2.1MHz Switching Frequency with Three Modes of Operation 25µA Ultra-Low Quiescent Current SKIP Mode Forced Fixed-Frequency Operation External Frequency Synchronization o Optional Spread-Spectrum Frequency Modulation o Power-Good Output o Enable-Pin Compatible from +3.3V Logic Level to +42V o Thermal Shutdown Protection o -40°C to +125°C Automotive Temperature Range o 10-Pin TDFN-EP or 16-Pin TSSOP-EP Packages The MAX16904 is available in a thermally enhanced, 3mm x 3mm, 10-pin TDFN package or a 16-pin TSSOP package. The MAX16904 operates over the -40°C to +125°C automotive temperature range. o AEC-Q100 Qualified Ordering Information Applications Automotive Industrial Military PART SPREAD TEMP PINSPECTRUM RANGE PACKAGE MAX16904RATB__/V+ Disabled -40°C to 10 TDFN-EP* +125°C MAX16904RAUE__/V+ Disabled -40°C to 16 TSSOP-EP* +125°C MAX16904SATB__/V+ Enabled -40°C to 10 TDFN-EP* +125°C MAX16904SAUE__/V+ Enabled -40°C to 16 TSSOP-EP* +125°C High-Voltage Input-Power DC-DC Applications Note: Insert the desired suffix letters (from Selector Guide) into the blanks to indicate the output voltage. Alternative output voltages available upon request. +Denotes a lead(Pb)-free/RoHS-compliant package. /V denotes an automotive qualified part. *EP = Exposed pad. Selector Guide appears at end of data sheet. For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX16904 General Description 2.1MHz, High-Voltage, 600mA Mini-Buck Converter MAX16904 Typical Operating Circuits 33kΩ SUP 4.7µF VBAT LEVEL SIGNAL EN * MAX16904_50/V+ SYNC BST GND 0.1µF 4.7µH 5V AT 600mA PGOOD LX 10µF 20kΩ PGND BIAS OUTS 2.2µF 33kΩ SUP 4.7µF VBAT LEVEL SIGNAL EN * MAX16904_33/V+ SYNC BST GND 0.1µF 3.3µH 3.3V AT 600mA LX PGOOD 10µF 20kΩ PGND OUTS BIAS 2.2µF *PLACE INPUT SUPPLY CAPACITORS AS CLOSE AS POSSIBLE TO THE SUP PIN. SEE THE APPLICATIONS INFORMATION SECTION FOR MORE DETAILS. 2 2.1MHz, High-Voltage, 600mA Mini-Buck Converter (Voltages referenced to GND.) SUP, EN..................................................................-0.3V to +42V BST to LX..................................................................-0.3V to +6V LX..............................................................-0.3V to (VSUP + 0.3V) BST .........................................................................-0.3V to +47V OUTS ......................................................................-0.3V to +12V SYNC, PGOOD, BIAS............................................-0.3V to +6.0V PGND to GND .......................................................-0.3V to +0.3V LX Continuous RMS Current .................................................1.0A OUTS Short-Circuit Duration ......................................Continuous ESD Protection Human Body Model .........................................................±2kV Machine Model ..............................................................±200V Continuous Power Dissipation (TA = +70°C) TDFN (derate 24.4 mW/°C above +70°C)......................1951mW TSSOP (derate 26.1 mW/°C above +70°C) ...................2089mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 affect device reliability. PACKAGE THERMAL CHARACTERISTICS (Note 1) TDFN Junction-to-Ambient Thermal Resistance (θJA) ...........41°C/W Junction-to-Case Thermal Resistance (θJC) ..................9°C/W TSSOP Junction-to-Ambient Thermal Resistance (θJA) ........38.3°C/W Junction-to-Case Thermal Resistance (θJC) ..................3°C/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. ELECTRICAL CHARACTERISTICS (VSUP = +14V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER Supply Voltage Range Supply Current SYMBOL VSUP I SUP CONDITIONS (Note 2) MIN 3.5 42 EN = low 4 8 EN = high, no load 25 35 VUVLO Bias rising VUVLO,HYS Hysteresis Bias Voltage VBIAS Bias Current Limit IBIAS MAX 28 t < 1s EN = high, continuous, no switching UV Lockout TYP 1 2.8 3 V µA mA 3.2 0.4 +5.5V VSUP +42V UNITS 5 V V 10 mA BUCK CONVERTER VOUT = 5V, fixed frequency VOUT,5V Voltage Accuracy VOUT = 5V, SKIP mode (Note 3) VOUT = 3.3V, fixed frequency VOUT,3.3V VOUT = 3.3V, SKIP mode (Note 3) 6V VSUP 18V, ILOAD = 0 to 600mA, TA = -40°C to +125°C -2.0% 5 +2.5% -2.0% 5 +4% -2.0% 3.3 +2.5% -2.0% 3.3 +4% V 3 MAX16904 ABSOLUTE MAXIMUM RATINGS MAX16904 2.1MHz, High-Voltage, 600mA Mini-Buck Converter ELECTRICAL CHARACTERISTICS (continued) (VSUP = +14V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL SKIP-Mode Peak Current I SKIP High-Side DMOS RDSON R ON,HS Low-Side DMOS RDSON R ON,LS DMOS Peak Current-Limit Threshold Soft-Start Ramp Time LX Rise Time TYP MAX 350 VBIAS = 5V UNITS mA 400 800 m 250 450 m 0.85 1.05 1.22 A t SS 7 8 9 ms tRISE,LX t ON PWM Switching Frequency f SW Spread-Spectrum Range MIN IMAX Minimum On-Time SYNC Input Frequency Range CONDITIONS 5 80 Internally generated f SYNC SS ns 1.925 2.1 1.8 Spread-spectrum option only +6 VTHR,PGD VOUT rising 93 VTHF,PGD VOUT falling ns 2.275 MHz 2.6 MHz % PGOOD PGOOD Threshold PGOOD Debounce 88 tDEB 91 94 10 % µs PGOOD High Leakage Current ILEAK,PGD TA = +25°C 1 µA PGOOD Output Low Level VOUT,PGD Sinking 1mA 0.4 V LOGIC LEVELS EN Level EN Input Current SYNC Switching Threshold SYNC Internal Pulldown VIH,EN 2.4 0.6 VIL,EN I IN,EN VEN = V SUP = +42V, TA = +25°C VIH,SYNC 1 1.4 0.4 VIL,SYNC V µA V RPD,SYNC 200 k T SHDN 175 °C T SHDN,HYS 15 °C THERMAL PROTECTION Thermal Shutdown Thermal Shutdown Hysteresis Note 2: When the typical minimum on-time of 80ns is violated, the device skips pulses. Note 3: Guaranteed by design; not production tested. 4 2.1MHz, High-Voltage, 600mA Mini-Buck Converter NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE (SKIP MODE) 5V, FFF MODE 3.3V, FFF MODE 40 30 20 40 5V PART 30 20 3.3V PART 10 10 0 0.2 0.3 0.4 0 0.6 0.5 2 1 0 -1 -2 -3 6 8 10 12 14 16 18 20 22 24 26 28 LOAD CURRENT (A) 6 8 10 12 14 16 18 20 22 24 26 28 INPUT VOLTAGE (V) INPUT VOLTAGE (V) SHUTDOWN SUPPLY CURRENT vs. INPUT VOLTAGE LOAD REGULATION 4 3 SKIP MODE 2 1 0 FFF MODE -1 15 12 SUPPLY CURRENT (µA) 0.1 3 -4 MAX16904 toc04 0 4 -2 MAX16904 toc05 50 50 SUPPLY CURRENT (µA) 70 OUTPUT-VOLTAGE CHANGE (%) EFFICIENCY (%) 80 60 60 MAX16904 toc03 3.3V, SKIP MODE MAX16904 toc02 5V, SKIP MODE 90 MAX16904 toc01 100 LINE REGULATION (ILOAD = 600mA) OUTPUT VOLTAGE CHANGE (%) EFFICIENCY vs. LOAD CURRENT 9 6 3 -3 0 -4 0 0.1 0.2 0.3 0.4 0.5 6 0.6 STARTUP RESPONSE (ILOAD = 600mA) 1ms/div 8 10 12 14 16 18 20 22 24 26 28 INPUT VOLTAGE (V) LOAD CURRENT (A) SHUTDOWN WAVEFORM (ILOAD = 600mA) MAX16904 toc06 MAX16904 toc07 VEN 5V/div EN 5V/div IL 1A/div IINDUCTOR 0.5A/div VOUT 5V/div PGOOD 5V/div VPGOOD 5V/div VOUT 5V/div 20µs/div 5 MAX16904 Typical Operating Characteristics (VSUP = +14V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VSUP = +14V, TA = +25°C, unless otherwise noted.) LOAD TRANSIENT RESPONSE (3.3V, SKIP MODE) LOAD TRANSIENT RESPONSE (3.3V, FIXED MODE) MAX16904 toc09 MAX16904 toc08 600mA IL 500mA/div 100mA 600mA IL 500mA/div 100mA VOUT 50mV/div AC-COUPLED 5V VBIAS 5V/div VOUT 50mV/div AC-COUPLED 5V VBIAS 5V/div 5V VPGOOD 5V/div 5V VPGOOD 5V/div 40µs/div 40µs/div LOAD TRANSIENT RESPONSE (5V, SKIP MODE) LOAD TRANSIENT RESPONSE (5V, FIXED MODE) MAX16904 toc11 MAX16904 toc10 600mA IL 500mA/div 100mA 600mA IL 500mA/div 100mA VOUT 50mV/div AC-COUPLED VOUT 50mV/div AC-COUPLED 5V VBIAS 5V/div 5V VBIAS 5V/div 5V VPGOOD 5V/div 5V VPGOOD 5V/div 40µs/div 40µs/div UNDERVOLTAGE PULSE (COLD CRANK) STANDBY CURRENT vs. LOAD CURRENT MAX16904 toc12 MAX16904 toc13 500 450 VSUP 10V/div 400 350 VOUT 5V/div VPGOOD 5V/div IIN (µA) MAX16904 2.1MHz, High-Voltage, 600mA Mini-Buck Converter 300 250 200 150 100 ILOAD 500mA/div 50 0 10ms/div 0.01 0.1 ILOAD (mA) 6 1 2.1MHz, High-Voltage, 600mA Mini-Buck Converter TOP VIEW BST 1 SUP 2 LX 3 PGND 4 OUTS 5 + MAX16904 EP 10 EN 9 GND 8 BIAS 7 SYNC 6 PGOOD TDFN + BST 1 16 N.C. SUP 2 15 EN SUP 3 14 GND LX 4 LX 5 12 SYNC PGND 6 11 PGOOD PGND 7 OUTS 8 MAX16904 13 BIAS 10 N.C. EP 9 N.C. TSSOP Pin Description PIN TDFN-EP TSSOP-EP 1 1 NAME FUNCTION BST Bootstrap Capacitor for High-Side Driver (0.1µF) Voltage Supply Input. Connect a 4.7µF ceramic capacitor from SUP to PGND. Place the capacitor very close to the SUP pin. For the TSSOP-EP package, connect both SUP pins together for proper operation. 2 2, 3 SUP 3 4, 5 LX 4 6, 7 PGND Power Ground. For the TSSOP-EP package, connect both PGND pins together for proper operation. 5 8 OUTS Buck Regulator Voltage-Sense Input. Bypass OUTS to PGND with a 10µF or larger X7R ceramic capacitor. 6 11 PGOOD 7 12 SYNC 8 13 BIAS +5V Internal Logic Supply. Connect a 2.2µF ceramic capacitor from BIAS to GND. 9 14 GND Analog Ground 10 15 EN 9, 10, 16 N.C. EP Buck Switching Node. LX is high impedance when the device is off. For the TSSOP package, connect both LX pins together for proper operation. Open-Drain Power-Good Output. External pullup resistor required for automatic SKIP mode operation. Sync Input. SYNC allows the device to synchronize to other supplies. When connected to GND or unconnected, SKIP mode is enabled under light loads. When connected to a clock source or BIAS, forced PWM mode is enabled. Enable Input. EN is high-voltage compatible. Drive EN HIGH for normal operation. No Connection. Not internally connected. Exposed Pad. Connect EP to PGND. Do not use EP as the only ground connection. 7 MAX16904 Pin Configurations 2.1MHz, High-Voltage, 600mA Mini-Buck Converter MAX16904 Functional Diagram SYNC REF EN HVLDO BANDGAP OSC BST BIAS SUP CLK HSD SOFT-START CURRENT-SENSE AND SLOPE COMPENSATION LOGIC CONTROL LX BIAS OUTS PWM LSD EAMP COMP VGOOD MAX16904 PGND PGOOD 8 GND 2.1MHz, High-Voltage, 600mA Mini-Buck Converter The MAX16904 is a small, current-mode buck converter that features synchronous rectification and requires no external compensation network. The device is designed for 600mA output current, and can stay in dropout by running at 97% duty cycle. It provides an accurate output voltage within the +6.5V to +18V input range. Voltage quality can be monitored by observing the PGOOD signal. The device operates at 2.1MHz (typ) frequency, which allows for small external components, reduced output ripple, and guarantees no AM band interference. The device features an ultra-low 25µA (typ) quiescent supply current in standby mode. Standby mode is entered when load currents are below 5mA and when SYNC is low. The device operates from a +3.5V to +28V supply voltage and tolerates transients up to +42V, making it ideal for automotive applications. The device is available in factory-trimmed output voltages from 1.8V to 10.7V in 100mV steps. Contact the factory for availability of voltage options. Enable (EN) The device is activated by driving EN high. EN is compatible from a +3.3V logic level to automotive battery levels. EN can be controlled by microcontrollers and automotive KEY or CAN inhibit signals. The EN input has no internal pullup/pulldown current to minimize overall quiescent supply current. To realize a programmable undervoltage lockout level, use a resistordivider from SUP to EN to GND. BIAS/UVLO The device features undervoltage lockout. When the device is enabled, an internal bias generator turns on. LX begins switching after VBIAS has exceeded the internal undervoltage lockout level VUVLO = 3V (typ). Soft-Start The device features an internal soft-start timer. The output voltage soft-start ramp time is 8ms (typ). If a short circuit or undervoltage is encountered, after the softstart timer has expired, the device is disabled for 30ms (typ) and it reattempts soft-start again. This pattern repeats until the short circuit has been removed. Oscillator/Synchronization and Efficiency (SYNC) The device has an on-chip oscillator that provides a switching frequency of 2.1MHz (typ). Depending on the condition of SYNC, two operation modes exist. If SYNC is unconnected or at GND, the device must operate in highly efficient pulse-skipping mode if the load current is below the SKIP mode current threshold. If SYNC is at BIAS or has a frequency applied to it, the device is in forced PWM mode. The device offers the best of both worlds. The device can be switched during operation between forced PWM mode and SKIP mode by switching SYNC. SKIP Mode Operation SKIP mode is entered when the SYNC pin is connected to ground or is unconnected and the peak load current is < 350mA (typ). In this mode, the high-side FET is turned on until the current in the inductor is ramped up to 350mA (typ) peak value and the internal feedback voltage is above the regulation voltage (1.2V typ). At this point, both the high-side and low-side FETs are turned off. Depending on the choice of the output capacitor and the load current the high-side FET turns on when OUTS (valley) drops below the 1.2V (typ) feedback voltage. Achieving High Efficiency at Light Loads The device operates with very low quiescent current at light loads to enhance efficiency and conserve battery life. When the device enters SKIP mode the output current is monitored to adjust the quiescent current. When the output current is < 5mA, the device operates in the lowest quiescent current mode also called the standby mode. In this mode, the majority of the internal circuitry (excluding that necessary to maintain regulation) in the device, including the internal high-voltage LDO, is turned off to save current. Under no load and with SKIP mode enabled, the device draws only 25µA (typ) current. For load currents > 5mA, the device enters normal SKIP mode while still maintaining very high efficiency. Controlled EMI with Forced-Fixed Frequency In forced PWM mode, the device attempts to operate at a constant switching frequency for all load currents. For tightest frequency control, apply the operating frequency to SYNC. The advantage of this mode is a constant switching frequency, which improves EMI performance; the disadvantage is that considerable current can be thrown away. If the load current during a switching cycle is less than the current flowing through the inductor, the excess current is diverted to GND. With no external load present, the operating current is in the 10mA range. Extended Input Voltage Range In some cases, the device is forced to deviate from its operating frequency independent of the state of SYNC. For input voltages above 18V, the required duty cycle to regulate its output may be smaller than the minimum on-time (80ns, typ). In this event, the device is forced to lower its switching frequency by skipping pulses. 9 MAX16904 Detailed Description MAX16904 2.1MHz, High-Voltage, 600mA Mini-Buck Converter If the input voltage is reduced and the device approaches dropout, it tries to turn on the high-side FET continuously. To maintain gate charge on the highside FET, the BST capacitor must be periodically recharged. To ensure proper charge on the BST capacitor when in dropout, the high-side FET is turned off every 6.5µs and the low-side FET is turned on for about 150ns. This gives an effective duty cycle of > 97% and a switching frequency of 150kHz when in dropout. Spread-Spectrum Option The device has an optional spread-spectrum version. If this option is selected, then the internal operating frequency varies by +6% relative to the internally generated operating frequency of 2.1MHz (typ). Spread spectrum is offered to improve EMI performance of the device. By varying the frequency 6% only in the positive direction, the device still guarantees that the 2.1MHz frequency does not drop into the AM band limit of 1.8MHz. Additionally, with the low minimum on-time of 80ns (typ) no pulse skipping is observed for a 5V output with 18V input maximum battery voltage in steady state. The internal spread spectrum does not interfere with the external clock applied on the SYNC pin. It is active only when the device is running with internally generated switching frequency. Power-Good (PGOOD) The device features an open-drain power-good output. PGOOD is an active-high output that pulls low when the output voltage is below 91% of its nominal value. PGOOD is high impedance when the output voltage is above 93% of its nominal value. Connect a 20kΩ (typ) pullup resistor to an external supply or the on-chip BIAS output. Overcurrent Protection The device limits the peak output current to 1.05A (typ). To protect against short-circuit events, the device shuts off when OUTS is below 1.5V (typ) and one overcurrent event is detected. The device attempts a soft-start restart every 30ms and stays off if the short circuit has not been removed. When the current limit is no longer present, it reaches the output voltage by following the normal soft-start sequence. If the device die reaches the thermal limit of +175°C (typ) during the current-limit event, it immediately shuts off. Thermal-Overload Protection The device features thermal-overload protection. The device turns off when the junction temperature exceeds 10 +175°C (typ). Once the device cools by 15°C (typ), it turns back on with a soft-start sequence. Applications Information Inductor Selection Three key inductor parameters must be specified for operation with the device: inductance value (L), peak inductor current (IPEAK), and inductor saturation current (ISAT). The minimum required inductance is a function of operating frequency, input-to-output voltage differential, and the peak-to-peak inductor current (∆IP-P). Higher ∆IP-P allows for a lower inductor value, while a lower ∆IP-P requires a higher inductor value. A lower inductor value minimizes size and cost, improves large-signal and transient response, but reduces efficiency due to higher peak currents and higher peak-topeak output-voltage ripple for the same output capacitor. On the other hand, higher inductance increases efficiency by reducing the ripple current. Resistive losses due to extra wire turns can exceed the benefit gained from lower ripple current levels especially when the inductance is increased without also allowing for larger inductor dimensions. A good compromise is to choose ∆IP-P equal to 30% of the full load current. Use the following equation to calculate the inductance: L= VOUT (VIN − VOUT ) VIN × fSW × ∆IP − P VIN and VOUT are typical values so that efficiency is optimum for typical conditions. The switching frequency is ~2.1MHz. The peak-to-peak inductor current, which reflects the peak-to-peak output ripple, is worse at the maximum input voltage. See the Output Capacitor section to verify that the worst-case output ripple is acceptable. The inductor saturation current is also important to avoid runaway current during continuous output short circuit. The output current may reach 1.22A since this is the maximum current limit. Choose an inductor with a saturation current of greater than 1.22A to ensure proper operation and avoid runaway. Input Capacitor The discontinuous input current of the buck converter causes large input ripple current. The switching frequency, peak inductor current, and the allowable peak-topeak input-voltage ripple dictate the input capacitance requirement. Increasing the switching frequency or the inductor value lowers the peak-to-average current ratio yielding a lower input capacitance requirement. The input ripple comprises mainly of ∆VQ (caused by the capacitor discharge) and ∆VESR (caused by the 2.1MHz, High-Voltage, 600mA Mini-Buck Converter I × D(1 − D) CIN = OUT ∆VQ × fSW where: ∆IP − P = (VIN − VOUT ) × VOUT VIN × fSW × L and: V D = OUT VIN where IOUT is the output current, D is the duty cycle, and f SW is the switching frequency. Use additional input capacitance at lower input voltages to avoid possible undershoot below the UVLO threshold during transient loading. Output Capacitor The allowable output-voltage ripple and the maximum deviation of the output voltage during step load currents determine the output capacitance and its ESR. The output ripple comprises of ∆VQ (caused by the capacitor discharge) and ∆VESR (caused by the ESR of the output capacitor). Use low-ESR ceramic or aluminum electrolytic capacitors at the output. For aluminum electrolytic capacitors, the entire output ripple is contributed by ∆VESR. Use the ESROUT equation to calculate the ESR requirement and choose the capacitor accordingly. If using ceramic capacitors, assume the contribution to the output ripple voltage from the ESR and the capacitor discharge to be equal. The following equations show the output capacitance and ESR requirement for a specified output-voltage ripple. ESR = COUT = ∆VESR ∆IP − P ∆IP − P 8 × ∆VQ × fSW where: ∆IP − P = (VIN − VOUT ) × VOUT VIN × fSW × L VOUT _ RIPPLE ≅ ∆VESR + ∆VQ ∆IP-P is the peak-to-peak inductor current as calculated above and fSW is the converter’s switching frequency. The allowable deviation of the output voltage during fast transient loads also determines the output capacitance and its ESR. The output capacitor supplies the step load current until the converter responds with a greater duty cycle. The response time (t RESPONSE ) depends on the closed-loop bandwidth of the converter. The device’s high switching frequency allows for a higher closed-loop bandwidth, thus reducing tRESPONSE and the output capacitance requirement. The resistive drop across the output capacitor’s ESR and the capacitor discharge causes a voltage droop during a step load. Use a combination of low-ESR tantalum and ceramic capacitors for better transient load and ripple/noise performance. Keep the maximum output-voltage deviations below the tolerable limits of the electronics being powered. When using a ceramic capacitor, assume an 80% and 20% contribution from the output capacitance discharge and the ESR drop, respectively. Use the following equations to calculate the required ESR and capacitance value: ESROUT = ∆VESR ISTEP I × tRESPONSE COUT = STEP ∆VQ where I STEP is the load step and t RESPONSE is the response time of the converter. The converter response time depends on the control-loop bandwidth. PCB Layout Guidelines Careful PCB layout is critical to achieve low switching power losses and clean stable operation. Use a multilayer board wherever possible for better noise immunity. Refer to the MAX16904 Evaluation Kit for recommended PCB layout. Follow these guidelines for a good PCB layout: 1) The input capacitor (4.7µF, see the applications schematic in the Typical Operating Circuits) should be placed right next to the SUP pins (pins 2 and 3 on the TSSOP-EP package). Because the device operates at 2.1MHz switching frequency, this placement is critical for effective decoupling of high-frequency noise from the SUP pins. 11 MAX16904 ESR of the input capacitor). The total voltage ripple is the sum of ∆VQ and ∆VESR. Assume the input-voltage ripple from the ESR and the capacitor discharge is equal to 50% each. The following equations show the ESR and capacitor requirement for a target voltage ripple at the input: ∆VESR ESR = ∆IP − P ⎞ ⎛ ⎜⎝ IOUT + ⎟ 2 ⎠ MAX16904 2.1MHz, High-Voltage, 600mA Mini-Buck Converter 2) Solder the exposed pad to a large copper plane area under the device. To effectively use this copper area as heat exchanger between the PCB and ambient, expose the copper area on the top and bottom side. Add a few small vias or one large via on the copper pad for efficient heat transfer. Connect the exposed pad to PGND ideally at the return terminal of the output capacitor. 3) Isolate the power components and high current paths from sensitive analog circuitry. 4) Keep the high current paths short, especially at the ground terminals. The practice is essential for stable jitter-free operation. 5) Connect the PGND and GND together preferably at the return terminal of the output capacitor. Do not connect them anywhere else. 1MΩ CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE CS 100pF ESD Protection The device’s ESD tolerance is rated for Human Body Model and Machine Model. The Human Body Model discharge components are CS = 100pF and RD = 1.5kΩ (Figure 1). The Machine Model discharge components are CS = 200pF and RD = 0Ω (Figure 2). RD 1.5kΩ RD 0Ω CHARGE-CURRENTLIMIT RESISTOR DISCHARGE RESISTANCE STORAGE CAPACITOR Figure 1. Human Body ESD Test Circuit 12 6) Keep the power traces and load connections short. This practice is essential for high efficiency. Use thick copper PCB to enhance full load efficiency and power dissipation capability. 7) Route high-speed switching nodes away from sensitive analog areas. Use internal PCB layers as PGND to act as EMI shields to keep radiated noise away from the device and analog bypass capacitor. DEVICE UNDER TEST HIGHVOLTAGE DC SOURCE CS 200pF DISCHARGE RESISTANCE STORAGE CAPACITOR Figure 2. Machine Model ESD Test Circuit DEVICE UNDER TEST 2.1MHz, High-Voltage, 600mA Mini-Buck Converter OUTPUT VOLTAGE (V) PIN-PACKAGE SPREAD-SPECTRUM SWITCHING FREQUENCY TOP MARK MAX16904RATB50+ 5.0 10 TDFN-EP* (3mm x 3mm x 0.75mm) ⎯ AYG MAX16904RATB50/V+ 5.0 10 TDFN-EP* (3mm x 3mm x 0.75mm) ⎯ AVY MAX16904RAUE50/V+ 5.0 16 TSSOP-EP* (5mm x 4.4mm) ⎯ ⎯ MAX16904SATB50/V+ 5.0 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AWA MAX16904SATB51/V+† 5.1 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AYX MAX16904SATB52/V+† 5.2 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AYY MAX16904SAUE50/V+ 5.0 16 TSSOP-EP* (5mm x 4.4mm) Yes ⎯ MAX16904RATB33/V+ 3.3 10 TDFN-EP* (3mm x 3mm x 0.75mm) ⎯ AVX MAX16904RAUE33/V+ 3.3 16 TSSOP-EP* (5mm x 4.4mm) ⎯ ⎯ MAX16904SATB33/V+ 3.3 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AVZ MAX16904SAUE33/V+ 3.3 16 TSSOP-EP* (5mm x 4.4mm) Yes ⎯ MAX16904RAUE18/V+† 1.8 16 TSSOP-EP* (5mm x 4.4mm) ⎯ ⎯ MAX16904SATB60/V+† 6.0 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AYO MAX16904SATB80/V+† 8.0 10 TDFN-EP* (3mm x 3mm x 0.75mm) Yes AYN PART Note: All devices operate over the -40°C to +125°C automotive temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. /V denotes an automotive qualified part. *EP = Exposed pad. †Future product–contact factory for availability. Chip Information PROCESS: BiCMOS Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 10 TDFN-EP T1033+1 21-0137 90-0003 16 TSSOP-EP U16E+3 21-0108 90-0120 13 MAX16904 Selector Guide MAX16904 2.1MHz, High-Voltage, 600mA Mini-Buck Converter Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 9/10 Initial release — 1 11/10 Added new output voltage trim to Selector Guide 12 2 3/11 Updated the Voltage Accuracy and the DMOS Peak Current-Limit Threshold parameters in the Electrical Characteristics, updated TOCs 1, 6, and 8–13 3 7/11 Added the MAX16904RATB50+ part number to the Selector Guide 13 4 3/12 Added new future part numbers to the Selector Guide 13 5 6/12 Updated Selector Guide to include MAX16904SATB51/V+ and the MAX16904SATB52/V+ 13 3, 4, 5, 6 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 14 _______________Maxim Integrated Products, Inc. 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 © 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.