SC5832A

深圳市中广芯源科技有限公司 SC5832A /a85T High Efficiency 1MHz 2A Synchronous Step Down Regulator Description Features The SC5832A is a high efficiency, high frequency synchronous DC-DC step-down converter. The 100% duty cycle feature provides low dropout operation, extending battery life in portable systems.  The internal synchronous switch increases efficiency and eliminates the need for external Schottky diode. At shutdown mode, the input supply current is less than 1µA. The current limit protection and on-chip thermal shutdown features provide protection against any combination of overload or ambient temperature.         Low RDS(ON) for Internal Switch (Top/Bottom): 180/100mΩ 2.5V~6.5V Input Voltage Range 2A Output Current 1MHz Switching Frequency Minimizes the External Components Internal Soft-Start Limits the Inrush Current Internal Compensation Function 100% Dropout Operation RoHS Compliant and Halogen Free SOT-23-5 Applications     Set Top Box LCD TV Tablet Portable Equipment Pin Assignments Ordering Information S5 Package (SOT-23-5) SC5832A□□□ TR: Tape/Reel FB VIN C: Green 5 4 (Marking) 1 2 3 Package Type S5: SOT-23-5 EN GND LX SOT-23-5 Marking Figure 1. Pin Assignment of SC5832A Part Number Product Code SC5832AS5C fiW 1 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Typical Application Circuit NC SC5832 EN Figure 2. Schematic Diagram VOUT 3.3V 2.5V 1.8V 1.5V 1.2V 1.05V C1 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC R1 453kΩ 316kΩ 200kΩ 150kΩ 100kΩ 75kΩ R2 100kΩ 100kΩ 100kΩ 100kΩ 100kΩ 100kΩ L1 μH μH 1.8μH 1.5μH 1.5μH 1.2μH C3 22μF MLCC 22μF MLCC 22μF MLCC 22μF MLCC 22μF MLCC 22μF MLCC Table 1. Recommended Component Values 2 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Functional Pin Description Pin Name Pin No. (SOT-23-5) EN 1 GND 2 LX 3 Power Switching Output. and low side NMOS VIN 4 Power Supply Input Pin. Drive VIN pin by 2.5V to 6.5V voltage to power on the chip. FB 5 Voltage Feedback Input Pin. Connect FB and VOUT with a resistive voltage divider. This IC senses feedback voltage via FB and regulates it at 0.6V. Pin Function Enable ontrol. this pin floating. Pull C high to turn the IC on, and pull low to disable the IC ’ Don t leave . Ground Pin. Connect an inductor to the drains of internal high side PMOS . Block Diagram EN VIN 1MΩ Undervoltage Lockout Bias Supply Enable Control Slope Compensation FB COMP EA Control Logic Current Limit Logic Control and Driver Logic 1 X LX Compensation VREF Soft Start Oscillator COMP GND Figure 3. Block Diagram of SC5832A 3 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Absolute Maximum Ratings (Note 1) ● VIN to GND --------------------------------------------------------------------------------------------------- -0.3V to +6.5V ● LX to GND --------------------------------------------------------------------------------------------------- -0.3V to (VIN+0.3) ● EN, FB, PG to GND ---------------------------------------------------------------------------------------- -0.3V to VIN ● Package hermal esistance, (θJA) SOT-23-5 ------------------------------------------------------------------------------------------ +250ºC/W ● Package hermal esistance, (θJC) SOT-23-5 ------------------------------------------------------------------------------------------ +130°C/W ● Maximum Junction Temperature (TJ) ------------------------------------------------------------------- +150°C ● Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------- +260°C ● Storage Temperature (TSTG) ------------------------------------------------------------------------------ -65°C to +150℃ Note 1：Stresses beyond those listed under “Absolute Maximum atings" may cause permanent damage to the device Recommended Operating Conditions (Note 2) ● Supply Voltage (VIN) ---------------------------------------------------------------------------------------- +2.5V to +5.5V ● Junction Temperature Range ---------------------------------------------------------------------------- -40°C to +125°C ● Ambient Temperature Range ----------------------------------------------------------------------------- -40°C to +85°C Note 2：The device is not guaranteed to function outside its operating conditions. 4 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Electrical Characteristics (VIN=5V, TA=25°C, unless otherwise specified.) Parameter Input Voltage Range Symbol VIN Shutdown Current ISHDN Quiescent Current Iq Reference Voltage VREF FB Input Leakage Current P-Channel MOSFET On-Resistance (Note 3) N-Channel MOSFET On-Resistance (Note 3) Conditions IFB Min Typ 2.5 EN=GND 0.1 VFB=0.65V, IOUT=0A 80 0.588 VFB=VIN Max Unit 5.5 V 1 μA μA 0.6 0.612 V 0.01 1 µA RDS(ON) 180 mΩ RDS(ON) 100 mΩ P-Channel Current Limit (Note 3) ILIM 2.1 A EN High-Level Input Voltage VIH 1.5 V EN Low-Level Input Voltage VIL Under Voltage Lockout Voltage 0.4 V UVLO 2.4 V UVLO Hysteresis VHYS 0.2 V Oscillation Frequency FOSC IOUT=500mA 0.8 Minimum On Time 100 VOUT Discharge Resistance Internal Soft Start Time 1.2 50 Maximum Duty Cycle Thermal Shutdown Temperature (Note 3) 1 TSD TSS MHz ns % 100 Ω 150 °C 1 ms Note 3：Guarantee by design. 5 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T 100 90 95 Efficiency (%) 95 85 80 75 90 85 80 VOUT=3.3V VOUT=1.2V 70 75 VIN=3.3V VIN=5V 65 VIN=4.2V VIN=5V 70 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 2 0.2 0.4 0.6 Load Current (A) 0.8 1 1.2 1.4 1.6 1.8 2 80 100 Load Current (A) Figure 4. Efficiency vs. Load Current Figure 5. Efficiency vs. Load Current 612 1.2 609 1.15 606 1.1 Frequency (MHz) Feedback Voltage (mV) Efficiency (%) Typical Performance Curves 603 600 597 594 1.05 1 0.95 0.9 VIN=5V IOUT=0.5A 591 VIN=5V IOUT=0.5A 0.85 588 0.8 -40 -20 0 20 40 60 80 Temperature (°C) Figure 6. Feedback Voltage vs. Temperature 100 -40 -20 0 20 40 60 Temperature (°C) Figure 7. Frequency vs. Temperature 6 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Function Description The SC5832A is a high efficiency, internal compensation and constant frequency current mode step-down synchronous DC/DC converter. It has integrated high-side (180mΩ, typ) and low-side (100mΩ, typ) power switches, and provides 2A continuous load current. It regulates input voltage from 2.5V to 5.5V, and down to an output voltage as low as 0.6V. Control Loop Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load, line response, protection of the internal main switch and synchronous rectifier. The SC5832A switches at a constant frequency (1MHz) and regulates the output voltage. During each cycle, the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until next cycle starts. Enable The SC5832A EN pin provides digital control to turn on/off the regulator. When the voltage of EN exceeds the threshold voltage, the regulator will start the soft start function. If the EN pin voltage is below the shutdown threshold voltage, the regulator will turn into the shutdown mode and the shutdown current will be smaller than μA. For auto start-up operation, connect EN to VIN. Short Circuit Protection The SC5832A provides short circuit protection function to prevent the device damaged from short condition. When the short condition occurs and the feedback voltage drops lower than 40% of the regulation level, this will activate the latch protection circuit. Then output will be forced shutdown to prevent the inductor current runaway and to reduce the power dissipation within the IC under true short circuit conditions. Once the short condition is removed, reset EN or VIN to restart IC. Over Current Protection The SC5832A over current protection function is implemented by using cycle-by-cycle current limit architecture. The inductor current is monitored by measuring the high-side MOSFET series sense resistor voltage. When the load current increases, the inductor current will also increase. When the peak inductor current reaches the current limit threshold, the output voltage will start to drop. When the over current condition is removed, the output voltage will return to the regulated value. Over Temperature Protection The SC5832A incorporates an over temperature protection circuit to protect itself from overheating. When the junction temperature exceeds the thermal shutdown threshold temperature, the regulator will be shutdown. And the hysteretic of the over temperature protection is 30°C (typ). Soft Start The SC5832A employs internal soft start function to reduce input inrush current during start up. The internal soft start time will be 1ms. Under Voltage Lockout When the SC5832A is power on, the internal circuits will be held inactive until VIN voltage exceeds the UVLO threshold voltage. And the regulator will be disabled when VIN is below the UVLO threshold voltage. The hysteretic of the UVLO comparator is 200mV (typ). 7 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Application Information Output Voltage Setting The output voltage VOUT is set by using a resistive divider from the output to FB. The FB pin regulated voltage is 0.6V. Thus the output voltage is: A low ESR capacitor is required to keep the noise minimum. Ceramic capacitors are better, but tantalum or low ESR electrolytic capacitors may also suffice. Output Capacitor Selection Table 2 lists recommended values of R1 and R2 for most used output voltage. Table 2 Recommended Resistance Values VOUT R1 R2 3.3V 453kΩ 100kΩ 2.5V 316kΩ 100kΩ 1.8V 200kΩ 100kΩ 1.5V 150kΩ 100kΩ 1.2V 100kΩ 100kΩ The output capacitor is used to keep the DC output voltage and supply the load transient current. When operating in constant current mode, the output ripple is determined by four components: PPL t PPL C t PPL PPL ( SL) t S S t t The following figures show the form of the ripple contributions. VRIPPLE(ESR)(t) Place resistors R1 and R2 close to FB pin to prevent stray pickup. Input Capacitor Selection The use of the input capacitor is filtering the input voltage ripple and the MOSFETS switching spike voltage. Because the input current to the step-down converter is discontinuous, the input capacitor is required to supply the current to the converter to keep the DC input voltage. The capacitor voltage rating should be 1.25 to 1.5 times greater than the maximum input voltage. The input capacitor ripple current RMS value is calculated as: ( MS) + VRIPPLE(ESL) (t) (t) + VRIPPLE(C) (t) (t) + VNOISE (t) (t) Where D is the duty cycle of the power MOSFET. This function reaches the maximum value at D=0.5 and the equivalent RMS current is equal to IOUT/2. The following diagram is the graphical representation of above equation. = VRIPPLE(t) IIN(RMS) (A) 1.2 1 2A (t) 0.8 0.6 0.4 1A 0.5A 0.2 0 10 20 30 40 50 60 70 80 90 D (%) 8 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Application Information (Continued) PPL ( SL) PPL (C) F SC S L SL L SL F SC That will lower ripple current and result in lower output ripple voltage. The Δ L is inductor peak-to-peak ripple current: L F SC L The following diagram is an example to graphically represent Δ L equation. L C Where FOSC is the switching frequency, L is the inductance value, VIN is the input voltage, ESR is the equivalent series resistance value of the output capacitor, ESL is the equivalent series inductance value of the output capacitor and the COUT is the output capacitor. Low ESR capacitors are preferred to use. Ceramic, tantalum or low ESR electrolytic capacitors can be used depending on the output ripple requirements. When using the ceramic capacitors, the ESL component is usually negligible. It is important to use the proper method to eliminate high frequency noise when measuring the output ripple. The figure shows how to locate the probe across the capacitor when measuring output ripple. Remove the scope probe plastic jacket in order to expose the ground at the tip of the probe. It gives a very short connection from the probe ground to the capacitor and eliminates noise. Probe Ground ΔIL (A) PPL ( S ) 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 L=1.2μH L=1.5μH L=2.2μH 2.5 3 3.5 5.5 A good compromise value between size and efficiency is to set the peak-to-peak inductor ripple current Δ L equal to 30% of the maximum load current. But setting the peak-to-peak inductor ripple current Δ L between 20%~50% of the maximum load current is also acceptable. Then the inductance can be calculated with the following equation: L GND 5 VOUT=1.2V, FOSC=1MHz L VOUT 4 4.5 VIN (V) (MA ) F SC L To guarantee sufficient output current, peak inductor current must be lower than the SC5832 high-side MOSFET current limit. The peak inductor current is shown as below: Ceramic Capacitor P A (MA ) L Inductor Selection The output inductor is used for storing energy and filtering output ripple current. But the trade-off condition often happens between maximum energy storage and the physical size of the inductor. The first consideration for selecting the output inductor is to make sure that the inductance is large enough to keep the converter in the continuous current mode. 9 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Application Information (Continued) VOUT R1 SC5832A C3 FB R2 C 2. Place feedback resistors close to the FB pin. 3. Keep the sensitive signal (FB) away from the switching signal (LX). 4. Multi-layer PCB design is recommended. GND FC VOUT C2 L1 C1 VIN VIN FB C3 For optimizing the feedforward capacitor, knowing the cross frequency is the first thing. The cross frequency (or the converter bandwidth) can be determined by using a network analyzer. When getting the cross frequency with no feedforward capacitor identified, the value of feedforward capacitor C3 can be calculated with the following equation: PCB Layout Recommendation he device’s performance and stability are dramatically affected by PCB layout. It is recommended to follow these general guidelines shown as below: 1. Place the input capacitors and output capacitors as close to the device as possible. The traces which connect to these capacitors should be as short and wide as possible to minimize parasitic inductance and resistance. R1 Feedforward Capacitor Selection Internal compensation function allows users saving time in design and saving cost by reducing the number of external components. The use of a feedforward capacitor C3 in the feedback network is recommended to improve transient response or higher phase margin. 4 5 3 LX 2 GND 1 EN R2 SS Figure 19. Recommended Layout Diagram Where FCROSS is the cross frequency. To reduce transient ripple, the feedforward capacitor value can be increased to push the cross frequency to higher region. Although this can improve transient response, it also decreases phase margin and causes more ringing. In the other hand, if more phase margin is desired, the feedforward capacitor value can be decreased to push the cross frequency to lower region. In general, the feedforward capacitor range is between 10pF to 330pF. 10 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn 深圳市中广芯源科技有限公司 SC5832A /a85T Outline Information SOT-23-5 Package (Unit: mm) SYMBOLS UNIT A DIMENSION IN MILLIMETER MIN MAX 0.90 1.45 A1 0.00 0.15 A2 0.90 1.30 B 0.30 0.50 D 2.80 3.00 E 2.60 3.00 E1 1.50 1.70 e 0.90 1.00 e1 1.80 2.00 L 0.30 0.60 Note：Followed From JEDEC MO-178-C. Carrier Dimensions 11 TEL:0755-27668758/29469758 web:http://www.zgsemi.com www.086ic.cn