RT9184 Preliminary 500mA Dual LDO Regulator General Description Features The RT9184 is a dual-channel, low noise, and low z Up to 500mA Output Current (Each LDO) dropout regulator supplying up to 500mA current at z Current Limiting and Thermal Protection each channel. The output voltage ranges from 1.5V z Short Circuit Protection to 3.3V in 100mV increment and 2% accuracy by z 650mV Dropout at 500mA Load operating from a +2.7V to +6.5V input. z Two LDOs in Power SOP-8 Package The RT9184 uses two internal PMOS as the pass device, which consumes 185µA supply current (both LDOs on) independent of load current and dropout Pin Configurations Part Number conditions. Other features include a current limiting RT9184 CH and over temperature protection. (Plastic PSOP-8) Pin Configurations TOP VIEW Applications z Desktop Computers z CD-RW z LCD Monitor z Information Appliance GND 1 8 VIN GND 2 7 VIN GND 3 6 VOUT1 5 NC VOUT2 4 Typical Application Circuit Ordering Information RT9184 VOUT2 VOUT2 VOUT1 Package type H : PSOP-8 Operating temperature range 10 µF VOUT1 RT9184 GND VIN 10 µF 10 µF C : Commercial standard Output voltage A : 3.3V (Output1), 1.8V (Output2) B : 3.3V (Output1), 2.5V (Output2) Other voltage versions please contact RichTek for detail. DS9184-00 March 2002 www.richtek-ic.com.tw 1 RT9184 Preliminary Pin Description Pin Name Pin Function VIN Power Input GND Ground VOUT1 Output1 Voltage VOUT2 Output2 Voltage NC No Connected Function Block Diagram Current Limit Thermal Protection + VOUT1 Vref + _ VOUT2 Bias www.richtek-ic.com.tw 2 Current Limit _ VIN GND DS9184-00 March 2002 RT9184 Preliminary Absolute Maximum Ratings z Input Voltage z Package Thermal Resistance 7V PSOP-8, θJC 28°C/W z Junction Temperature Range -40°C ~ 125°C z Storage Temperature Range -65°C ~ 150°C z Operating Temperature Range -40°C ~ 85°C z Lead Temperature (Soldering, 10 sec.) 260°C Electrical Characteristics (VIN = 5V, CIN = COUT = 10µF, typical values at TA = 25°C, for each LDO unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Units 2.7 -- 6.5 V Input Voltage Range VIN Output Voltage Accuracy ∆VOUT IOUT = 1mA -2 -- +2 % Maximum Output Current IMAX Continuous 500 -- -- mA Current Limit ILIMIT RLOAD = 1Ω 510 -- 1000 mA IG No Load -- 185 260 µA VDROP IOUT = 500mA -- 650 -- mV Line Regulation ∆VLINE VIN = (VOUT +0.4V or 2.7V) to 6.5V IOUT = 1mA -0.2 -- +0.2 %/V Load Regulation ∆VLOAD IOUT = 1mA to 500mA -35 -20 +5 mV 125 180 -- °C -- 20 -- °C -- 62 -- dB GND Pin Current (Whole Chip) Dropout Voltage Note Thermal Shutdown Temperature Thermal Shutdown Hysteresis Output Voltage AC PSRR TSD 100Hz, COUT = 10µF ILOAD = 100mA Note : Dropout voltage definition: VIN – VOUT when VOUT is 50mV below the value of VOUT (normal) DS9184-00 March 2002 www.richtek-ic.com.tw 3 RT9184 Preliminary Typical Operating Characteristics ILOAD = 100mA, VIN = 5V, COUT = 10µF, and CIN = 10µF, unless otherwise noted. Quiescent Current vs. Temp. Output Voltage Accuracy vs. Temp. 200 1.0 0.8 0.6 Output Voltage (%) Quiescent Current (µ A) 180 160 140 120 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 100 -1.0 -40 -15 10 35 Temperature ( °C) 60 85 -40 85 ILOAD = 1mA 50 80 PSRR (dB) Channel Isolation (dB) 60 40 40 30 20 10 RLOAD = 100Ω 100 1K 10K Frequency (Hz) 100K 1M 0 10 100 1K 10K 100K 1M Frequency (Hz) Load Transient Response (ILOAD = 10 to 500mA) Line Transient Response T 20mV/Div Output Voltage Deviation (AC-Coupled) Input Voltage (V) 60 60 20 VOUT 3> TT 1> ≈ 4.5 ≈ TT 3.5 TT ILOAD 1> 2↓ www.richtek-ic.com.tw 4 35 PSRR vs. Frequency 70 100 0 10 Temperature ( ° C) Channel-to-Channel Isolation vs. Frequency 120 -15 50µS/Div Time COUT = 100µF 1) Ch 1: 1 Volt 250 us 500mA 3) Ref B: 50 mVolt 250 us Time DS9184-00 March 2002 Preliminary RT9184 Functional Description The RT9184 integrate two low noise, low dropout, and low quiescent current linear regulators. Output voltages are optional ranging from 1.5V to 3.3V, and each channel can supply current up to 500mA. Internal P-Channel Pass Transistor The RT9184 features double typical 1.3Ω P-channel MOSFET pass transistors. It provides several advantages over similar designs using PNP pass transistors. The P-channel MOSFET requires no base drive, which reduces quiescent current significantly than PNP-based regulator, which wastes considerable current in dropout when the pass transistor saturates. They also use high base-drive currents under large loads. The RT9184 does not suffer from these problems and consume only 185µA of quiescent current whether in dropout, light-load, or heavy-load applications. Current Limit and Thermal Protection The RT9184 includes two independent current limit structure which monitor and control each pass transistor’s gate voltage limiting the guaranteed maximum output current to 510mA minimum. Thermal-overload protection limits total power dissipation in the RT9184. When the junction temperature exceeds TJ = +180°C, the thermal sensor signals the shutdown logic turning off the pass transistor and allowing the IC to cool down. The thermal sensor will turn the pass transistor on again after the IC’s junction temperature cools by 20°C, resulting in a pulsed output during continuous thermal-overload conditions. Thermal-overloaded protection is designed to protect the RT9184 in the event of fault conditions. Do not exceed the absolute maximum junction-temperature rating of TJ = +125°C for continuous operation. The output can be shorted to ground for an indefinite amount of time without damaging the part by cooperation of current limit and thermal protection. DS9184-00 March 2002 www.richtek-ic.com.tw 5 RT9184 Preliminary Applications Information two components of the output response: a DC shift Capacitor Selection and Regulator Stability Like any low-dropout regulator, the external capacitors used with the RT9184 must be carefully selected for regulator stability and performance. from the output impedance due to the load current change, and the transient response. The DC shift is quite small due to the excellent load regulation of the IC. Typical output voltage transient spike for a step Using a capacitor whose value is greater than 1µF on change in the load current from 0mA to 50mA is tens the RT9184 input and the amount of capacitance can mV, depending on the ESR of the output capacitor. be increased without limit. The input capacitor must Increasing be located a distance of not more than 0.5" from the decreasing the ESR attenuates the overshoot. input pin of the IC and returned with a clean analog ground. Any good quality ceramic or tantalum can be used for this capacitor. The capacitor with larger value and lower ESR (equivalent series resistance) provides better PSRR and line-transient response. the output capacitor’s value and Input-Output (Dropout) Voltage A regulator’s minimum input-output voltage differential (or dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this will determine the useful end-of-life battery The RT9184 is designed specifically to work with low voltage. Because the RT9184 uses a P-channel ESR ceramic output capacitor in space-saving and MOSFET pass transistor, the dropout voltage is a performance function of drain-to-source on-resistance [RDS(ON)] consideration. Using a ceramic capacitor whose value is at least 1µF on the RT9184 output ensures the stability. The RT9184 still works well with output capacitor of other types due to the wide stable ESR range. Output capacitor of larger capacitance can reduce noise and improve loadtransient response, stability, and PSRR. The output capacitor should be located not more than 0.5" from the VOUT pin of the RT9184 and returned with a clean analog ground. multiplied by the load current. Reverse Current Path The power transistor used in the RT9184 has an inherent diode connected between each regulator input and output (see Fig.1). If the output is forced above the input by more than a diode-drop, this diode will become forward biased and current will flow from the VOUT terminal to VIN. This diode will also be turned on by abruptly stepping the input voltage to a Note that some ceramic dielectrics exhibit large value below the output voltage. To prevent regulator capacitance and ESR variation with temperature. It mis-operation, a Schottky diode could be used in the may be necessary to use 2.2µF or more to ensure applications where input/output voltage conditions stability at temperatures below -10°C in this case. can cause the internal diode to be turned on (see Also, tantalum capacitors, 2.2µF or more may be Fig.2). As shown, the Schottky diode is connected in needed to maintain capacitance and ESR in the parallel with the internal parasitic diode and prevents stable region for strict application environment. it from being turned on by limiting the voltage drop Tantalum capacitors maybe suffer failure due to across it to about 0.3V < 100mA to prevent damaging surge current when it is connected to a low- the part. impedance source of power (like a battery or very large capacitor). If a tantalum capacitor is used at the input, it must be guaranteed to have a surge current rating sufficient for the application by the VIN VOUT manufacture. Load-Transient Considerations The RT9184 load-transient response graphs show www.richtek-ic.com.tw 6 Fig. 1 VOUT Structure of RT9184 DS9184-00 March 2002 RT9184 Preliminary Gold Wire Die Polymide Tape VIN VOUT Fig. 2 External Schottky Diode to Prevent Internal Exposed Slug Leadframe Diode Turning on Fig. 3 Power SOP-8 Structure Power Dissipation and PCB Layout Note The maximum power dissipation of RT9184 depends 8 7 6 5 1 2 3 4 on the thermal resistance from the case to circuit board, the temperature difference between the die junction and ambient air, and the rate of airflow. The power dissipation across the device is P = IOUT (VIN - VOUT). The maximum power dissipation is: Fig. 4 Typical Footprint of RT9184 PMAX = (TJ - TA) / θJA where TJ - TA is the temperature difference between the RT9184 die junction and the ambient environment, θJA is the thermal resistance from the junction to the ambient environment. The GND pin of the RT9184 performs the dual function of providing an electrical connection to ground and channeling heat away. Connect the GND pin to ground using a large pad or ground plane. The RT9184 is assembled by power SOP-8 package with direct slug solder to PCB (Fig.3). This structure offers a low thermal resistance of junction to case (θJC) and can dissipate the heat away by proper PCB layout (a proper θCA, thermal resistance of case to ambient). Because the bottom slug of RT9184 plays the role as ground, the footprint in Fig.4 is a typical configuration for heat dissipating copper clad. Medium power dissipations of up to 2W are easily obtainable in practice with this configuration. The heat dissipating copper area on the PCB can be configured in various shapes and sized depending upon the particular application. DS9184-00 March 2002 www.richtek-ic.com.tw 7 RT9184 Preliminary Package Information H A M J B X Y F C D Symbol I Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 4.801 4.950 0.189 0.195 B 3.810 3.988 0.150 0.157 C 1.470 1.730 0.058 0.068 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.190 0.250 0.007 0.009 I 0.050 0.150 0.002 0.006 J 5.791 6.198 0.228 0.244 M 0.380 1.270 0.015 0.050 X 1.830 2.290 0.072 0.090 Y 1.830 2.290 0.072 0.090 Power 8–Lead SOP Plastic Package www.richtek-ic.com.tw 8 DS9184-00 March 2002 Preliminary DS9184-00 March 2002 RT9184 www.richtek-ic.com.tw 9 RT9184 Preliminary RICHTEK TECHNOLOGY CORP. RICHTEK TECHNOLOGY CORP. Headquarter Taipei Office (Marketing) 6F, No. 35, Hsintai Road, Chupei City 8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5510047 Fax: (8863)5537749 Tel: (8862)89191466 Fax: (8862)89191465 Email: [email protected] www.richtek-ic.com.tw 10 DS9184-00 March 2002