Single Channel Linear Controller

Transcription

1 Single Channel Linear Controller Description The is a low dropout linear voltage regulator controller with IC supply power (VCC) under voltage lockout protection, external power N-MOSFET drain voltage (VD) under voltage lockout protection, a built-in thermal shutdown circuit, Soft-start function, and a timer latch short circuit protection function. Enable function places the device in standby, reducing quiescent supply current to less than 1µA. The device is available in both adjustable and fixed output voltage versions. The comes in a miniature 8-pin MSOP package. Features Non Rush Current on Start-up Drive External N-Channel MOSFET Adjustable Output Voltage or Fixed Output Voltages Built-in Thermal Shutdown IC Supply Power (VCC) UVLO Protection External Power N-MOSFET Drain Voltage (VD) UVLO Protection Timer Latch Short Circuit Very Low Shutdown Current MSOP-8 Package RoHS Compliant Applications Mother Boards Notebook PCs Game Machines Pin Assignments MS Package (MSOP-8) TOP VIEW 1.NRCS 2.GND 3.EN 4.VCC 5.VFB 6.VS 7.EXT 8.VD Figure 1. Pin Assignment of Ordering Information - TR: Tape / Reel Blank: Tube G: Green Package Type MS: MSOP-8 Output Voltage: Blank: Adjustable 12:1.2V 15:1.5V -1.0-SEP

2 Typical Application Circuit & Block Diagram Figure 2. Typical Application Circuit and Function Block of ADJ version VCC C1 10µF VCC VIN EN Enable Reference Block UVLO VCC UVLO VD VD R4 4KΩ R3 4KΩ C2 100µF Vref EXT 220Ω 22nF OPTIONAL Thermal Protection Protection Block VS VO C4 220µF VFB Soft Start and SCP Control R2 RB R1 RA NRCS C3 0.1µF GND Figure 3. Typical Application Circuit and Function Block of FIX version -1.0-SEP

3 Functional Pin Description Pin Name NRCS GND EN VCC VFB VS EXT VD Pin Function Soft-Start and Timer Latch Short Circuit Protection Pin. Connect an external capacitor to adjust timer. Ground. Enable Pin. Supply Voltage Input. Input Voltage Range from 4.5V to 5.5V. Feedback Voltage Input Pin for ADJ version. Output Voltage input Pin for fix version. Output Voltage Discharge Pin. External MOSFET Driver Output. Detect External Power MOSFET Supply Voltage Pin. Absolute Maximum Ratings V CC, NRCS, EN, VFB, VS, EXT, VD to GND V to + 6V Maximum Junction Temperature (T J ) Storage Temperature (T STG ) to Power T A =25, MSOP-8 (P D ) mW Package Thermal Resistance, MSOP-8 (θ JA ) C/W Lead Temperature (Soldering, 10sec.) Note:Stresses beyond those listed under Absolute Maximum Ratings" may cause permanent damage to the device. Recommended Operating Conditions Supply Voltage (VCC) V to + 5.5V Drain Voltage (VD) V to + 5.5V Enable Input Voltage (VEN) V to + 5.5V Capacitor on NRCS Terminal nF to 1µF Voltage on NRCS Terminal V to + 2.5V Operation Temperature Range (T OPR ) C to + 85 C -1.0-SEP

4 Electrical Characteristics (VCC=5V, VIN=3.3V, VEN=3V, EN=VIN, T A = 25 ºC, unless otherwise specified) Parameter Symbol Conditions Min Typ. Max Unit Bias Current I CC ma Shut Down Mode Current I SD VEN=0V 0 1 µa Line Regulation Reg.I VCC=4.5V to 5.5V %/V Load Regulation Reg.L Io=0 to 3A mv Enable EN High Level Input Voltage V ENH 2 V EN Low Level Input Voltage V ENL 0.8 V EN Input Leakage Current I EN VEN=3V 0 1 µa Feedback Voltage Feedback Voltage V FB Io=50mA V VFB Input Bias Current I FB VFB=3V 80 na Source Voltage VS Input Bias Current IS BIAS ma VS Discharge Current IS DIS VS=1V, VEN=0V 110 ma Output MOSFET Driver MOSFET Driver Source Current I GSO VFB=0.6V,VEXT=2.5V ma MOSFET Driver Sink Current I GSI VFB=0.7V,VEXT=2.5V ma UVLO VCC UVLO V CC UVLO V CC Sweep up V VCC UVLO Hysterisis V CC HYS V CC Sweep down mv VD UVLO V D UVLO VD Sweep up Vox0.6 Vox0.7 Vox0.8 V Drain Voltage Sensing VD Input Bias Current I VD 0 na NRCS / SCP NRCS Charge Current I NRCS VNRCS=0.5V µa SCP Charge Current I SCPCH VNRCS=0.5V µa SCP Discharge Current I SCPDI VNRCS=0.5V 0.3 ma SCP Threshold Voltage V SCP V Short Detect Voltage V OSCP Vox0.3 Vox0.35 Vox0.4 V NRCS Standby Voltage V STB 50 mv -1.0-SEP

5 Typical Performance Curves Reference Voltage (mv) Soft start current (ua) Temperature ( o C) Figure 4. Reference Voltage vs. Junction Temperature Temperature ( o C) Figure 5. Soft start current vs. temperature I LOAD =0mA to 500mA Figure 6. Load Transient Response I LOAD =0mA to 3A Figure 7. Load Transient Response CH1:EN CH1:EN CH2:NRCS CH2:NRCS CH3:V OUT CH3:V OUT CH4:I IN CH4:I IN Figure 8. Star-up Waveform Figure 9. Star-up Waveform -1.0-SEP

6 Applications Information The is a low-dropout, low-quiescent current linear controller designed for 3C product applications. The consists of a highly accurate band gap core, error amplifier, soft start, fast discharge and an internal feedback voltage divider. The band gap reference is connected to the error amplifier s inverting input. The error amplifier compares this reference with the feedback voltage and amplifies the difference. If the feedback voltage is lower than the reference voltage, the pass transistor gate is pulled high. This allows more current to pass to the output and increases the output voltage. If the feedback voltage is too high, the pass transistor gate is pulled low, allowing less current to pass to the output. The output voltage is feedback through an internal/ external resistor voltage divider connected to the VOUT. Additional blocks include a over temperature protection, and shutdown logic. Besides, a timer latch short circuit protection and on chip thermal shutdown features provide protection against any combination of over-load or ambient temperature that could cause junction temperature exceeding maximum rating. 1.Output and Input Capacitor The controller is designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability. Larger value of the output capacitor decreases the peak deviations and provides to improve transition response for larger current changes. The capacitor types (polymer, ceramic, and tantalum) have different characterizations such as temperature and voltage coefficients. All ceramic capacitors were manufactured with a variety of dielectrics, each with different behavior across temperature and applications. It is recommended to use 220uF polymer capacitors with 30mΩ to 50mΩ ESR range between device outputs to ground for transient stability. So the ESR of output capacitor is very important because it generates a zero to provide phase lead for loop stability. There are no requirements for the ESR on the input capacitor, but its voltage and temperature coefficient have to be considered for device application environment. 2. Timer Latch Short Circuit Protection The includes a timer latch short circuit protection function. It monitors the output voltage and NRCS pin voltage to protect IC from output short to ground. If the output voltage goes below 35% of the nominal value, the constant current charges NRCS -1.0-SEP-2008 pin cap until NRCS s level beyond the setting voltage to obtain a SCP delay time. The timer latch source current for SCP is 20 μa (typ.), and the time-up voltage is also 1.3 V (typ.). The controller latches the MOSFET drivers to avoid breakdown of power MOSFET. The SCP delay time used to latch the MOSFET drivers is decided by the value of the NRCS capacitor. The internal circuitry can be turned on again after the IC cycle the input power or cycle EN pin signal to clear the SCP latch. 3.Quick Discharge The has built-in a quick discharge circuitry to protect system function correct operation This discharge block discharges output capacitor quickly to avoid low output voltage level to affect system s MCU abnormal work when IC power off or enable pin pulls down. 4.Dropout Voltage The minimum dropout voltage of LDO determines the lowest usable supply voltage. In PCs-powered systems, this determines the useful end-of-life battery voltage. Because the use a N-channel MOSFET pass transistor, their dropout voltage is a function of drain-to-source on resistance (RDS(on)) multiplied by the load current 5.Over Temperature Protection Over temperature protection limits total power dissipation in the. When the junction temperature exceeds T j = +160 C, the thermal sensor signals the shutdown logic and turns off the pass transistor. The thermal sensor turns the pass transistor on again after the IC s junction temperature drops by 30 C, resulting in a pulsed output during continuous thermal-overload conditions. Thermal-Overload protection is design to protect the in the event of a fault condition. For continual operation, do not exceed the absolute maximum junction temperature rating of Tj = +150 C. 6.Under Voltage Lockout For under voltage lockout (UVLO), the monitors VCC and VD pin voltages. When the VCC voltage is lower than 4.19V or VD pin voltage is lower than 70% of the output voltage. the UVLO comparator output goes low to turn off the controller. 6

7 Applications Information (Continued) 7.Soft Start The NRCS pin connecting a 0.1uF capacitor could suppress inrush current and get a gradual increase of output voltage during power up, after both VCC and VD voltage is above the under-voltage lockout threshold and EN is set to high. As the internal constant current source charges the external NRCS capacitor to compare with feedback voltage to control gate voltage of pass transistor. Therefore, output voltage increases following this reference voltage to the nominal value of regulation. The internal circuit will discharge NRCS pin s charge when soft start function has been finished. 8.Enable Input Operation The is turned off by pulling the EN pin low and turned on by pulling it high. The Enable input is TTL/CMOS compatible threshold for simple logic interfacing. If this feature is not used, the EN pin should be connected to VCC to keep the regulator output available at all time. 9.Fixed and Adjusting Output Voltage is including fixed and adjusting output voltage version. The fixed version just has 1.2V and 1.5V type. The adjusting version is required an external resistor divider to divide the output voltage down to the nominal reference voltage. Current drawn by the resistor network should be limited to maintain the overall regulator efficiency. The maximum value of the resistor network is limited by the feedback input bias current and the potential for noise being coupled into the feedback pin. A resistor network in the order of 10kΩ is recommended. The controller output voltage is determined by the following relationship: 10.Compensation N-MOSFET regulators have a lower output impedance (compared to an P-MOSFET regulator), which results in a pole-zero pair being formed by every different capacitor connected to the output. The zero frequency is approximately: Fz = 1 / (2 X π X ESR X C) Where ESR is the equivalent series resistance of the capacitor, and C is the value of capacitance. The pole frequency is: Fp = 1 / (2 X π X RL X C) Where RL is the load resistance connected to the regulator output. 11.Layout Consideration 1. Place ceramic C1 capacitor near the VCC pin as possible. 2. Place polymer C4 capacitors near the VS pin and source terminal of power MOSFET as possible. 3. Expand the copper connected to the GND for thermal design of power N-MOS can assist in spreading heat to the PCB. 4. Use wide traces and trace length is short as possible to VIN and VO. V OUT R R = VFB 1 where V FB =0.65V as specified SEP

8 Outline Information MSOP- 8 Package (Unit: mm) SYMBOLS DIMENSION IN MILLIMETER UNIT MIN NOM MAX A A A b C D E E e L θ 0º --- 8º Note 1: Followed From JEDEC MO-187-E. Life Support Policy Fitipower s products are not authorized for use as critical components in life support devices or other medical systems SEP