View RT9184_484025.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Preliminary
RT9184
500mA Dual LDO Regulator
General Description
The RT9184 is a dual-channel, low noise, and low dropout regulator supplying up to 500mA current at each channel. The output voltage ranges from 1.5V to 3.3V in 100mV increment and 2% accuracy by operating from a +2.7V to +6.5V input. The RT9184 uses two internal PMOS as the pass device, which consumes 185A supply current (both LDOs on) independent of load current and dropout conditions. Other features include a current limiting and over temperature protection.
Features
Up to 500mA Output Current (Each LDO) Current Limiting and Thermal Protection Short Circuit Protection 650mV Dropout at 500mA Load Two LDOs in Power SOP-8 Package
Pin Configurations
Part Number RT9184 CH (Plastic PSOP-8) Pin Configurations TOP VIEW
GND 1 GND 2 GND 3 VOUT2 4
8 VIN 7 VIN 6 VOUT1 5 NC
Applications
Desktop Computers CD-RW LCD Monitor Information Appliance
Typical Application Circuit
VOUT2 VOUT2 VOUT1 10 F VOUT1
Ordering Information
RT9184 Package type H : PSOP-8 Operating temperature range 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.
RT9184
GND VIN 10 F 10 F
DS9184-00 March 2002
www.richtek-ic.com.tw
1
RT9184
Pin Description
Pin Name VIN GND VOUT1 VOUT2 NC Ground Output1 Voltage Output2 Voltage No Connected Pin Function Power Input
Preliminary
Function Block Diagram
VIN
Current Limit
Thermal Protection
Current Limit
+
VOUT1
Bias
www.richtek-ic.com.tw
2
_
_
Vref
+
VOUT2
GND
DS9184-00 March 2002
Preliminary Absolute Maximum Ratings
Input Voltage Package Thermal Resistance PSOP-8, JC Junction Temperature Range Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec.)
RT9184
7V 28C/W -40C ~ 125C -65C ~ 150C -40C ~ 85C 260C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 10F, typical values at TA = 25C, for each LDO unless otherwise specified.) Parameter Input Voltage Range Output Voltage Accuracy Maximum Output Current Current Limit GND Pin Current (Whole Chip) Dropout Voltage Line Regulation Load Regulation Thermal Shutdown Temperature Thermal Shutdown Hysteresis Output Voltage AC PSRR TSD 100Hz, COUT = 10F ILOAD = 100mA
Note
Symbol VIN VOUT IMAX ILIMIT IG VDROP VLINE
Test Conditions
Min 2.7
Typ ----185 650 --20 180 20 62
Max 6.5 +2 -1000 260 -+0.2 +5 ----
Units V % mA mA A mV %/V mV C C dB
IOUT = 1mA Continuous RLOAD = 1 No Load IOUT = 500mA VIN = (VOUT +0.4V or 2.7V) to 6.5V IOUT = 1mA
-2 500 510 ---0.2 -35 125 ---
VLOAD IOUT = 1mA to 500mA
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 = 10F, and CIN = 10F, unless otherwise noted.
Quiescent Current vs. Temp.
200 1.0 0.8
Output Voltage Accuracy vs. Temp.
Quiescent Current ( A)
180
0.6
Output Voltage (%)
-40 -15 35 Temperature ( C) 10 60 85
0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8
160
140
120
100
-1.0 -40 -15 10 35 60 85
Temperature ( C)
120 100
Channel-to-Channel Isolation vs. Frequency
70 60 50
PSRR vs. Frequency
ILOAD = 1mA
Channel Isolation (dB)
PSRR (dB)
RLOAD = 100 100 1K
80 60 40 20 0
40 30 20 10 0
Frequency (Hz)
10K
100K
1M
10
100
1K
10K
100K
1M
Frequency (Hz)
Output Voltage Deviation (AC-Coupled)
Line Transient Response
T
Load Transient Response (ILOAD = 10 to 500mA)
VOUT
3>
20mV/Div
1>
T T
Input Voltage (V)
4.5 3.5
2
T T
ILOAD 50S/Div Time
T T
1>
1) Ch 1: 1 Volt 250 us 500mA 3) Ref B: 50 mVolt 250 us
COUT = 100F Time DS9184-00 March 2002
www.richtek-ic.com.tw
4
Preliminary 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 1.3 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 185A 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 = +180C, 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 20C, 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 = +125C 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.
RT9184
DS9184-00 March 2002
www.richtek-ic.com.tw
5
RT9184
Applications Information
Capacitor Selection and Regulator Stability Like any low-dropout regulator, the
Preliminary
two components of the output response: a DC shift 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 change in the load current from 0mA to 50mA is tens mV, depending on the ESR of the output capacitor. Increasing the output capacitor's value and decreasing the ESR attenuates the overshoot. 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 voltage. Because the RT9184 uses a P-channel MOSFET pass transistor, the dropout voltage is a function of drain-to-source on-resistance [RDS(ON)] 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 value below the output voltage. To prevent regulator mis-operation, a Schottky diode could be used in the applications where input/output voltage conditions can cause the internal diode to be turned on (see Fig.2). As shown, the Schottky diode is connected in parallel with the internal parasitic diode and prevents it from being turned on by limiting the voltage drop across it to about 0.3V < 100mA to prevent damaging the part.
external
capacitors used with the RT9184 must be carefully selected for regulator stability and performance. Using a capacitor whose value is greater than 1F on the RT9184 input and the amount of capacitance can be increased without limit. The input capacitor must be located a distance of not more than 0.5" from the 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 RT9184 is designed specifically to work with low ESR ceramic output capacitor in space-saving and performance consideration. Using a ceramic capacitor whose value is at least 1F 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. Note that some ceramic dielectrics exhibit large capacitance and ESR variation with temperature. It may be necessary to use 2.2F or more to ensure stability at temperatures below -10C in this case. Also, tantalum capacitors, 2.2F or more may be needed to maintain capacitance and ESR in the stable region for strict application environment. Tantalum capacitors maybe suffer failure due to surge current when it is connected to a lowimpedance 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 manufacture. Load-Transient Considerations The RT9184 load-transient response graphs show
www.richtek-ic.com.tw
VIN
VOUT
Fig. 1 VOUT Structure of RT9184
DS9184-00 March 2002
6
Preliminary
RT9184
Gold Wire Die
Polymide Tape
VIN
VOUT
Fig. 2 External Schottky Diode to Prevent Internal Diode Turning on
Exposed Slug
Leadframe
Fig. 3 Power SOP-8 Structure Power Dissipation and PCB Layout Note The maximum power dissipation of RT9184 depends 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: PMAX = (TJ - TA) / JA where TJ - TA is the temperature difference between the RT9184 die junction and the ambient environment, JA 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 (JC) and can dissipate the heat away by proper PCB layout (a proper CA, 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. Fig. 4 Typical Footprint of RT9184
1 2 3 4 8 7 6 5
DS9184-00 March 2002
www.richtek-ic.com.tw
7
RT9184
Package Information
Preliminary
H A M
JB
Y
X
F
C D I
Symbol A B C D F H I J M X Y
Dimensions In Millimeters Min 4.801 3.810 1.470 0.330 1.194 0.190 0.050 5.791 0.380 1.830 1.830 Max 4.950 3.988 1.730 0.508 1.346 0.250 0.150 6.198 1.270 2.290 2.290
Dimensions In Inches Min 0.189 0.150 0.058 0.013 0.047 0.007 0.002 0.228 0.015 0.072 0.072 Max 0.195 0.157 0.068 0.020 0.053 0.009 0.006 0.244 0.050 0.090 0.090
Power 8-Lead SOP Plastic Package
www.richtek-ic.com.tw
DS9184-00 March 2002
8
Preliminary
RT9184
DS9184-00 March 2002
www.richtek-ic.com.tw
9
RT9184
Preliminary
RICHTEK TECHNOLOGY CORP.
Headquarter
6F, No. 35, Hsintai Road, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5510047 Fax: (8863)5537749
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek-ic.com.tw
www.richtek-ic.com.tw DS9184-00 March 2002
10

▲Up To Search▲

Price & Availability of RT9184

	To Download RT9184 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .