RTQ2132BGCP-QT

® RTQ2132B-QT 1.2A, 36V, 2.1MHz Synchronous Step-Down Converter General Description Features The RTQ2132B is a 1.2A, high-efficiency, current mode synchronous step-down converter which is optimized for automotive applications. The device operates with input voltages from 3V to 36V and is protected from load dump transients up to 42V, eases input surge protection design. The device can program the output voltage between 0.8V to VIN. The integrated low R DS(ON) power MOSFETs achieves high efficiency over the wide load range. The peak current mode control with simple external compensation allows the use of small inductors and results in fast transient response and good loop stability.  The RTQ2132B provides complete protection functions such as input under-voltage lockout, output-under voltage protection, over-current protection, and thermal shutdown. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. The RTQ2132B is available in TSSOP-14 (Exposed Pad) package.              Ordering Information RTQ2132B (- ) -QT Grade QT : AEC-Q100 Qualified Package Type CP : TSSOP-14 (Exposed Pad-Option 2)     Fixed Output Voltage 50 : 5V  Richtek products are :  Automotive Systems Car Camera Module and Car Cockpit Systems Connected Car Systems Point of Load Regulator in Distributed Power Systems Digital Set Top Boxes Broadband Communications Pin Configuration (TOP VIEW) RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.  Applications Lead Plating System G : Green (Halogen Free and Pb Free) Note :   AEC-Q100 Grade 1 Qualified Wide Input Voltage Range  3V to 36V Tight Switching Frequency Variation 2.1MHz ±10% Over Operating Ambient Temperature Wide Output Voltage Range : 0.8V to VIN 5V Fixed Output Voltage (see Ordering Information for availability) Maximum Output Current : 1.2A Peak Current Mode Control Integrated 200mΩ Ω Switch and 160mΩ Ω Synchronous Rectifier Built-In Spread-Spectrum Frequency Modulation for Low EMI Externally Adjustable Soft-Start Power Good Indication Enable Control 0.8V ±1.5% CV Reference Accuracy Adjacent Pin-Short Protection Built-In UVLO, UVP, OTP Suitable for use in SnPb or Pb-free soldering processes. VIN NC BOOT SW NC PGND SS 14 2 13 3 4 12 PAD 5 6 7 11 10 15 9 8 VCC PGOOD EN NC FB/VS COMP AGND TSSOP-14 (Exposed Pad) Copyright © 2018 Richtek Technology Corporation. All rights reserved. DSQ2132B-QT-01 August 2018 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RTQ2132B-QT Marking Information RTQ2132B-50GCP-QT RTQ2132BGCP-QT RTQ2132B50GCP-QT : Product Number RTQ2132BGCP-QT : Product Number RTQ2132B GCP-QTYMDNN RTQ2132B50 GCP-QTYMDNN YMDNN : Date Code YMDNN : Date Code Functional Pin Description Pin No. Pin Name Pin Function 1 VIN Power input. The input voltage range is from 3V to 36V after soft-start is finished. Connect input capacitors between this pin and PGND. It is recommended to use a 2.2F, X7R and a 0.1F, X7R capacitors. 2, 5, 11 NC No internal connection. 3 BOOT Bootstrap capacitor connection node to supply the high-side gate driver. Connect a 0.1F, X7R ceramic capacitor between this pin and SW pin. 4 SW Switch node. SW is the switching node that supplies power to the output and connect the output LC filter from SW to the output load. 6 PGND Power ground. 7 SS Soft-start capacitor connection node. Connect an external capacitor between this pin and ground to set the soft-start time. 8 AGND Analog ground. 9 COMP Compensation node. Connect external compensation elements to this pin to stabilize the control loop. 10 FB/VS Output voltage sense. There are two output voltage setting options : one is that trimmed output voltage options for a fixed output voltage are available for the VS pin, and the other is through a resistive divider to sense the output voltage at the FB pin. The feedback reference voltage is 0.8V typically. 12 EN Enable control input. A logic-high enables the converter; a logic-low forces the device into shutdown mode. 13 PGOOD Open-drain power-good indication output. Once soft-start is finished, PGOOD will be pulled low to ground if any internal protection is triggered. 14 VCC Linear regulator output. VCC is the output of the internal 5V linear regulator powered by VIN. Decouple with a 1F, X7R ceramic capacitor from VCC to ground for normal operation. 15 (Exposed Pad) PAD Exposed pad. The exposed pad is internally unconnected and must be soldered to a large PGND plane. Connect this PGND plane to other layers with thermal vias to help dissipate heat from the device. Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DSQ2132B-QT-01 August 2018 RTQ2132B-QT Functional Block Diagram Adjustable Output Voltage PGOOD - EN Enable Threshold UVLO + Enable Comparator 0.8V VCC HS Switch Current Comparator + EA + ISS 6µA BOOT SW Current Sense LS Switch Current Comparator PGND Slope Compensation Oscillator SS Current Sense Power Stage & Dead-time Control Fold-back Control FB Internal Regulator BOOT UVLO + PGOOD Threshold PGOOD Logic & Comparator Protection Control AGND VCC VIN COMP Fixed 5V Output Voltage PGOOD EN Enable Threshold UVLO + Enable Comparator VCC AGND HS Switch Current Comparator + EA + ISS 6µA SS Oscillator BOOT Slope Compensation SW LS Switch Current Comparator Current Sense PGND COMP Copyright © 2018 Richtek Technology Corporation. All rights reserved. DSQ2132B-QT-01 August 2018 Current Sense Power Stage & Dead-time Control Fold-back Control 0.8V Internal Regulator BOOT UVLO + PGOOD Logic & Threshold PGOOD Comparator Protection Control VS VCC VIN is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RTQ2132B-QT Operation Control Loop The RTQ2132B is a high efficiency step down converter utilizes the peak current mode control. An internal oscillator initiates turn-on of the high-side MOSFET switch. At the beginning of each clock cycle, the internal highside MOSFET switch turns on, allowing current to rampup in the inductor. The inductor current is internally monitored during each switching cycle. The output voltage is sensed on the FB pin via the resistor divider, R1 and R2, and compared with the internal reference voltage (VREF) to generate a compensation signal (VCOMP) on the COMP pin. A control signal derived from the inductor current is compared to the voltage at the COMP pin, derived from the feedback voltage. When the inductor current reaches its threshold, the high-side MOSFET switch is turned off and inductor current ramps-down. While the high-side switch is off, inductor current is supplied through the low-side MOSFET switch. This cycle repeats at the next clock cycle. In this way, duty-cycle and output voltage are controlled by regulating inductor current. Input Voltage Range The minimum on-time, tON_MIN, is the smallest duration of time in which the high-side MOSFET switch can be in its “on” state. Considering the minimum on-time, the allowed maximum input voltage, VIN_MAX, is calculated by : VOUT VIN_MAX  tON_MIN  fSW where the minimum on-time of the RTQ2132B is 60ns (typically) ; fSW is the maximum operating frequency. The maximum operating frequency of the RTQ2132B is 2.3MHz. In contrast, the minimum off-time determines the allowed minimum operating input voltage, VIN_MIN, to maintain the fixed frequency operation. The minimum off-time, tOFF_MIN, is the smallest amount of time that the RTQ2132B is capable of turning on the low-side MOSFET switch, tripping the current comparator and turning the MOSFET switch back off. Below shows minimum off-time calculation that considers the loss terms, Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 4   VOUT + IOUT_MAX  RDS(ON)_L + DCR VIN_MIN   1 tOFF_MIN  fsw    + IOUT_MAX  RDS(ON)_H  RDS(ON)_L      where the minimum off-time of the RTQ2132B is 65ns (typically) ; RDS(ON)_H is the on resistance of the high-side MOSFET switch; RDS(ON)_L is the on resistance of the low-side MOSFET switch; DCR is the DC resistance of inductor. Maximum Duty Cycle Operation The RTQ2132B is designed to operate in dropout at the high duty cycle approaching 100%. If the operational duty cycle is large and the required off time becomes smaller than minimum off time, the RTQ2132B starts to enable skip off time function and keeps high-side MOSFET switch on continuously. The RTQ2132B implements skip off time function to achieve high duty approaching 100%. Therefore, the maximum output voltage is near the minimum input supply voltage of the application. The input voltage at which the devices enter dropout changes depending on the input voltage, output voltage, switching frequency, load current, and the efficiency of the design. BOOT UVLO The BOOT UVLO circuit is implemented to ensure a sufficient voltage of BOOT capacitor for turning on the highside MOSFET switch at any condition. The BOOT UVLO usually actives at extremely high conversion ratio. With such conditions, the low-side MOSFET switch may not have sufficient turn-on time to charge the BOOT capacitor. The device monitors BOOT pin capacitor voltage and force to turn on the low-side MOSFET switch when the BOOT to SW voltage falls below VBOOT_UVLO_L (typically, 2.3V). Meanwhile, the minimum off time is extended to 100ns (typically) hence prolong the BOOT capacitor charging time. The BOOT UVLO is sustained until the VBOOT−SW is higher than VBOOT_UVLO_H (typically, 2.4V). Internal Regulator The device integrates a 5V linear regulator (VCC) that is supplied by VIN and provides power to the internal circuitry. is a registered trademark of Richtek Technology Corporation. DSQ2132B-QT-01 August 2018 RTQ2132B-QT The internal regulator operates in low dropout mode when VVIN is below 5V. The VCC can be used as the PGOOD pull-up supply but it is “NOT” allowed to power other device or circuitry. In many applications, a 1μF, X7R is recommended and it needs to be placed as close as possible to the VCC pin. Be careful to account for the voltage coefficient of ceramic capacitors when choosing the value and case size. Many ceramic capacitors lose 50% or more of their rated value when used near their rated voltage. the converter can have a monotonic smooth start-up. For soft-start control, the SS pin should never be left unconnected. After the SS pin voltage rises above 2V (typically), the PGOOD pin will be in high impedance and VPGOOD will be held high. The typical start-up waveform shown in Figure 1 indicate the sequence and timing between the output voltage and related voltage. VIN = 12V VIN VCC = 5V VCC Enable Control The RTQ2132B provides an EN pin, as an external chip enable control, to enable or disable the device. If VEN is held below a logic-low threshold voltage (VIL), switching is inhibited even if the VIN voltage is above VIN undervoltage lockout threshold (VUVLO). If VEN is held below 0.4V, the converter will enter into shutdown mode, that is, the converter is disabled. During shutdown mode, the supply current can be reduced to ISHDN (lower than 10μA). If the EN voltage rises above the logic-high threshold voltage (VIH) while the VIN voltage is higher than VUVLO, the device will be turned on, that is, switching being enabled and soft-start sequence being initiated. When VCC exceeds 5V, the current source typically sinks 1.2μA for VEN < 4V and up to 70μA for VEN > 4V. Soft-Start The soft-start function is used to prevent large inrush currents while the converter is being powered up. The RTQ2132B provides an SS pin so that the soft-start time can be programmed by selecting the value of the external soft-start capacitor CSS connected from the SS pin to AGND. During the start-up sequence, the soft-start capacitor is charged by an internal current source ISS (typically, 6μA) to generate a soft-start ramp voltage as a reference voltage to the PWM comparator. If the output is for some reasons pre-biased to a certain voltage during start-up, the device will not start switching until the voltage difference between SS pin and FB pin is larger than 400mV ( i.e. VSS − VFB > 400mV, typically). And only when this ramp voltage is higher than the feedback voltage VFB, the switching will be resumed. The output voltage can then ramp up smoothly to its targeted regulation voltage, and Copyright © 2018 Richtek Technology Corporation. All rights reserved. DSQ2132B-QT-01 August 2018 EN 0.2ms 0.4 x tSS tSS 2V SS 90% x VOUT VOUT PGOOD Figure 1. Start-Up Sequence Power Good Indication The RTQ2132B features an open-drain power-good output (PGOOD) to monitor the output voltage status. The output delay of comparator prevents false flag operation for short excursions in the output voltage, such as during line and load transients. Pull-up PGOOD with a resistor to VCC or an external voltage below 5.5V. The power-good function is activated after soft start is finished and is controlled by a comparator connected to the feedback signal VFB. If VFB rises above a power-good high threshold (VTH_PGLH1) (typically 90% of the reference voltage), the PGOOD pin will be in high impedance and VPGOOD will be held high after a certain delay elapsed. When VFB fall short of powergood low threshold (VTH_PGHL2) (typically 85% of the reference voltage) or exceeds VTH_PGHL1 (typically 120% of the reference voltage), the PGOOD pin will be pulled low. For VFB higher than VTH_PGHL1, VPGOOD can be pulled high again if VFB drops back by a power-good high threshold (VTH_PGLH2) (typically 117% of the reference voltage). Once being started-up, if any internal protection is triggered, PGOOD will be pulled low to GND. The internal open-drain pull-down device (1kΩ, typically) will pull the is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RTQ2132B-QT PGOOD pin low. The power good indication profile is shown in Figure 2. VTH_PGHL1 VTH_PGLH2 VTH_PGLH1 VTH_PGHL2 VFB peak current-limit protection against the condition that the inductor current increasing abnormally, even over the inductor saturation current rating. The inductor current through the high-side MOSFET switch will be measured after a certain amount of delay when the high-side MOSFET switch being turned on. If an over-current condition occurs, the converter will immediately turn off the high-side MOSFET switch and turn on the low-side MOSFET switch to prevent the inductor current exceeding the high-side MOSFET switch peak current limit (ILIM_H). Low-Side Switch Current-Limit Protection VPGOOD Figure 2. The Logic of PGOOD Spread-Spectrum Operation Due to the periodicity of the switching signals, the energy concentrates in one particular frequency and also in its harmonics. These levels or energy is radiated and therefore this is where a potential EMI issue arises. The RTQ2132B build-in spread-spectrum frequency modulation further helping systems designers with better EMC management. The spread spectrum can be active when soft-start is finished. The spread-spectrum is implemented by a pseudo random sequence and uses +6% spread of the switching frequency, that is, the frequency will vary from 2.1MHz to 2.226MHz. Therefore, the RTQ2132B still guarantees that the 2.1MHz switching frequency does not drop into the AM band limit of 1.8MHz. Input Under-Voltage Lockout In addition to the EN pin, the RTQ2132B also provides enable control through the VIN pin. If VEN rises above VIH first, switching will still be inhibited until the VIN voltage rises above VUVLO. It is to ensure that the internal regulator is ready so that operation with not-fully-enhanced internal MOSFET switches can be prevented. After the device is powered up, if the VIN voltage goes below the UVLO falling threshold voltage (VUVLO − ΔVUVLO), this switching will be inhibited; if VIN voltage rises above the UVLO rising threshold (VUVLO), the device will resume switching. High-Side Switch Peak Current-Limit Protection The RTQ2132B includes a cycle-by-cycle high-side switch Copyright © 2018 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 The RTQ2132B not only implements the high-side switch peak current limit but also provides the sourcing current limit and sinking current limit for low-side MOSFET switch. With these current protections, the IC can easily control inductor current at both side switch and avoid current runaway for short-circuit condition. For the low-side MOSFET switch sourcing current limit, there is a specific comparator in internal circuitry to compare the low-side MOSFET switch sourcing current to the low-side MOSFET switch sourcing current limit at the end of every clock cycle. When the low-side MOSFET switch sourcing current is higher than the low-side MOSFET switch sourcing current limit (typically,1.6A), the new switching cycle is not initiated until inductor current drops below the low-side MOSFET switch sourcing current limit. For the low-side MOSFET switch sinking current limit protection, it is implemented by detecting the voltage across the low-side MOSFET switch. If the low-side MOSFET switch sinking current exceeds the low-side MOSFET switch sinking current limit (typically,1A), both switches are off immediately, and it is held to stop switching until the beginning of next cycle. Output Under-Voltage Protection The RTQ2132B includes output under-voltage protection (UVP) against over-load or short-circuited condition by constantly monitoring the feedback voltage (VFB). If VFB drops below the under-voltage protection trip threshold (typically 50% of the internal reference voltage), the UV comparator will go high to turn off the internal high-side and keep low-side MOSFET switch turn on until inductor is a registered trademark of Richtek Technology Corporation. DSQ2132B-QT-01 August 2018 RTQ2132B-QT current drops to zero. If the output under-voltage condition continues for a period of time, the RTQ2132B enters output under-voltage protection with hiccup mode and discharges the CSS. During hiccup mode, the device remains shut down. After the SS pin voltage is discharged to less than 200mV (typically), the RT2132B attempts to re-start up again. The high-side MOSFET switch will start switching when voltage difference between SS pin and FB pin is larger than 400mV (i.e. VSS − VFB > 400mV, typically). If the fault condition is not removed, the high-side MOSFET switch stop switching when the voltage difference between SS pin and FB pin is 700mV (i.e. VSS − VFB = 700mV, typically). Upon completion of the soft-start sequence, if the fault condition is removed, the converter will resume normal operation; otherwise, such cycle for auto-recovery will be repeated until the fault condition is cleared. Hiccup mode allows the circuit to operate safely with low input current and power dissipation, and then resume normal operation as soon as the over-load or short-circuit condition is removed. A short circuit protection and recovery profile is shown in Figure 3. Output Short Short Removed Over-Temperature Protection The RTQ2132B includes an over temperature protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down switching operation when junction temperature exceeds a thermal shutdown threshold TSD. Once the junction temperature cools down by a thermal shutdown hysteresis (ΔTSD), the IC will resume normal operation with a complete soft-start. Pin-Short Protection The RTQ2132B provides pin-short protection for neighbor pins. The internal protection fuse will be burned out to prevent IC smoke, fire and spark when BOOT pin is shorted to VIN pin. The hiccup mode protection will be triggered to avoid IC burn-out when SW pin is shorted to ground during internal high-side MOSFET turns on. V OUT 2V/DIV VPGOOD 4V/DIV VSS, 4V/DIV ISW, 1A/DIV Figure 3. Short Circuit Protection and Recovery Copyright © 2018 Richtek Technology Corporation. All rights reserved. DSQ2132B-QT-01 August 2018 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RTQ2132B-QT Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN ---------------------------------------------------------------------------------------Switch Voltage, SW ----------------------------------------------------------------------------------------------