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RT9181
150mA LDO Regulator with PGOOD
General Description
The RT9181 is a low dropout voltage regulator with an output 2% accuracy and supply a continuous 150mA current within operating range from a +3V to +5.5V input. The power good function monitors the output voltage and indicates by pulling low the power good output (open drain). The RT9181 requires a small output capacitor with low ESR for stabilizing output voltage. The device also minimizes output overshoot during power up. The RT9181 uses an internal PMOS as the pass device, which consumes 160A supply current independent of load and dropout conditions. The EN pin controls the output and consumes no input bias current. Other features include current limiting, over temperature protection, and under voltage lockout.
Features
Low Dropout Voltage Regulator Up to 150mA Output Current Power Good (PGOOD) Function Chip Enable/Shutdown Function Load Independent, Low Quiescent Current, 160A Current Limiting and Thermal Protection Under Voltage Lockout (UVLO) Low Variation Due to Load and Line Regulation Output Stable with Low ESR Capacitors SOT-23-5 Package RoHS Compliant and 100% Lead (Pb)-Free
Applications
Processor Power-Up Sequencing Laptop, Notebook, and Palmtop Computers
Ordering Information
RT9181Package Type B : SOT-23-5 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) Output Voltage Default : 1.2V 18 : 1.8V
Pin Configurations
(TOP VIEW)
VIN GND EN 1 2 3 4 PGOOD 5 VOUT
SOT-23-5
Note : RichTek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating.
Typical Application Circuit
10K VIN 1
+
CIN 1uF
VIN
PGOOD
4
PGOOD
Chip Enable
3
EN
VOUT GND 2
5 COUT 1uF
Marking Information
For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail.
VOUT
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RT9181
Function Block Diagram
VIN EN Shutdown Control Thermal Control Gate Control Undervoltage Lockout Current Limit
VREF
+ -
VOUT
Output Voltage Detection GOOD Delay Timer PGOOD Fault Power Good Control GND
Functional Pin Description
Pin Name VIN GND EN PGOOD VOUT Pin Function Power Input Voltage Ground Chip Enable (Active High) Power Good Indicator Output Voltage
Timing Diagram
90% max of VOUT (normal) VPGOODH tD (PG) 2.0ms typ. VPGOODL 85% min of VOUT (normal)
VOUT
PGOOD
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RT9181
Absolute Maximum Ratings
(Note 1) Supply Input Voltage, VIN -------------------------------------------------------------------------------------------- 7V Enable Input Voltage -------------------------------------------------------------------------------------------------- 7V Power Good Output Voltage ---------------------------------------------------------------------------------------- 7V Power Dissipation, PD @ TA = 25C SOT-23-5 ---------------------------------------------------------------------------------------------------------------- 0.4W Package Thermal Resistance (Note 6) SOT-23-5, JA ----------------------------------------------------------------------------------------------------------- 250C/W Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260C Storage Temperature Range ---------------------------------------------------------------------------------------- -65C to 150C ESD Susceptibility (Note 2) HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 3)
Supply Input Voltage -------------------------------------------------------------------------------------------------- 3V to 5.5V Enable Input Voltage -------------------------------------------------------------------------------------------------- 0V to 5.5V Junction Temperature Range ---------------------------------------------------------------------------------------- -40C to 110C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 1F, TA = 25C, unless otherwise specified)
Parameter Output Voltage Accuracy Current Limit Quiescent Current Line Regulation Load Regulation EN Threshold (Note 4) Logic-Low Logic-High (Note 5)
Symbol VOUT ILIM IQ VLINE VLOAD VIL VIH
Test Conditions IOUT = 25mA IOUT = 0.1mA, TA = 0C to 70C (Note 4) RLOAD = 1 IOUT = 0mA VIN = 3V to 5.5V, IOUT = 0.1mA IOUT = 0.1mA to 150mA VIN = 3V to 5.5V, Shutdown VIN = 3V to 5.5V, Enable EN = GND or VIN EN = GND
Min -1.5 -2 160 90 -0.3 --2.0 0 0 85 -0 1 --
Typ --300 160 -1.5 ---0.01 ---2 1
Max Units 1.5 +2 -250 +0.3 +3 0.8 -100 1 -90 0.15 5 -mA A % % V V nA A % % V ms % %
EN Input Bias Current Shutdown Current Power Good Low Threshold Power Good High Threshold VPGOODL VPGOODH
Output falls % of VOUT (power NOT good) Output reaches % of VOUT, start delay timer (power good) VIN = 3.3V, IOL = 2mA, RDSON(max) = 75 Maximum voltage overshoot allowed on output during power-up
Power Good Output Logic Low VOL Delay Time to Power Good Power Up Overshoot
tD(PGOOD) See timing diagram VPGOODL
To be continued
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RT9181
Parameter Thermal Shutdown Temperature Thermal Shutdown Hysteresis Power Supply Rejection Rate Symbol TSD TSD PSRR f = 100Hz, COUT = 1F Test Conditions Min 110 --Typ 140 20 -62 Max Units ---C C dB
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. Regulation is measured at constant junction temperature by using a 20ms current pulse. Devices are tested for load regulation in the load range from 0.1mA to 150mA. Note 5. Quiescent, or ground current, is the difference between input and output currents. It is defined by IQ = IIN - IOUT under no load condition (IOUT = 0mA). The total current drawn from the supply is the sum of the load current plus the ground pin current. Note 6. JA is measured in the natural convection at T A = 25C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard.
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RT9181
Typical Operating Characteristics
Output Voltage vs. Temperature
1.210
Output Voltage vs. Supply Voltage
1.210
Output Voltage (V)
1.200
Output Voltage (V)
VIN = 5V IOUT = 0.1mA
1.205
1.205
1.200
1.195
1.195
IOUT = 0.1mA
1.190
80
1.190 -20 0 20 40 60
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Temperature (C)
Supply Voltage (V)
Current Limit vs. Temperature
400
400
Current Limit vs. Supply Voltage
Current Limit (mA)
350
300
Current Limit (mA)
VIN = 5V
-20 0 20 40 60 80
350
300
250
250
200
200 3 3.5 4 4.5 5 5.5 6
Temperature (C)
Supply Voltage (V)
Quiescent Current vs. Supply Voltage
180 175
180 175
Quiescent Current vs. Temperature
Quiescent Current (uA)
Quiescent Current (uA)
170 165 160 155 150 3.0 3.5 4.0 4.5 5.0 5.5 6.0
170 165 160 155
VIN = 5V
150 -20 0 20 40 60 80
Supply Voltage (V)
Temperature (C)
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RT9181
Line Transient Response
Output Voltage Deviation (mV) Output Voltage Deviation (mV)
40 20 0 -20 VIN = 4.5 to 5.5V COUT = 1uF IO = 10mA 4 2 0 -2
Line Transient Response
VIN = 4.5 to 5.5V COUT = 1uF IO = 150mA
Input Voltage Deviation (V)
Input Voltage Deviation (V)
5.5 4.5 RT9181-18
5.5 4.5 RT9181-18
Time (1ms/Div)
Time (1ms/Div)
Load Transient Response
Output Voltage Deviation (mV)
100 50 0 -50 VIN = 5V CIN = COUT = 1uF IO = 5 to 150mA
3.0 2.5 2.0 1.5 1.0 0.5
PGOOD Delay Time vs. Temperature
Load Current (mA)
200 100
0 RT9181-18
0.0
PGOOD Delay Time (ms) PG Delay Time (ms)
VIN = 5V
-20 0 20 40 60 80
Time (1ms/Div)
Temperature (C)
PGOOD Delay Time vs. Supply Voltage
3.00
UVLO Response at Power Up
Input Voltage (V)
4 2 0 1.5
PGOOD Delay Time (ms) PG Delay Time (ms)
2.50 2.00 1.50
Output Voltage (V)
1.00 0.50 0.00 3.0 3.5 4.0 4.5 5.0 5.5 6.0
1 0.5 0 COUT = 1uF
Time (5ms/Div)
Supply Voltage (V)
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RT9181
PGOOD Voltage PGOOD Voltage
PGOOD Response at Power Down
(V)
5 0 -5
PGOOD Response vs. VOUT
(V)
10 5 0
1.2V
Output Voltage (V)
Output Voltage (V)
1 0.5 0
2ms delay
0.5 0 VIN = 5V COUT = 1uF
VIN = 5V
Time (25us/Div)
Time (1ms/Div)
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RT9181
Application Information
EN The RT9181 is enabled by driving the EN input high, and shutdown by pulling the input low. If this feature is not to be used, the EN input should be tied to VIN to keep the regulator enabled at all times (the EN input must not be left floating). Internal P-Channel Pass Transistor The RT9181 features a P-Channel MOSFET pass transistors. It provides several advantages over similar designs using PNP pass transistors, including longer battery life. The P-Channel MOSFET requires no base drive, which reduces quiescent current considerably. PNP-based regulators waste considerable current in dropout when the pass transistor saturates, They also use high base-drive currents under large loads. The RT9181 does not suffer from these problems and consume only 160A of quiescent current whether in dropout, light-load, or heavy-load applications. Power Good The power good output is an open-drain output. It is designed essentially to work as a power-on reset generator once the regulated voltage was up or a fault condition. The output of the power good drives low when a fault condition occurs. The power good output come back up once the output has reached 90% of its nominal value and a 2ms (typ.) delay has passed. See Timing Diagram. The output voltage level will be drooped at the fault conditions including current limit, thermal shutdown, or shutdown and triggers the PGOOD detector to alarm a fault condition. This output is fed into an on-board delay circuitry that drives the open drain transistor to indicate a fault. Because at shutdown mode, a fault condition occurs by pulling the PGOOD output low, it will sink a current from the open drain and the external power. Selecting a suitable pulling resistance will be well to control this dissipated power. Current Limit and Thermal Protection The RT9181 includes a current limit structure which monitor and control the pass transistor's gate voltage limiting the guaranteed maximum output current to 160mA minimum. Thermal-overload protection limits total power dissipation in the RT9181. When the junction temperature exceeds TJ = +140C, the thermal sensor signals the shutdown logic turning off the pass transistor and allowing the IC to cool. 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 thermaloverload conditions. Thermal-overloaded protection is designed to protect the RT9181 in the event of fault conditions. Do not exceed the recommended maximum junction-temperature rating of TJ = +110C for continuous operation. The output can be shorted to ground for and indefinite amount of time without damaging the part by cooperation of current limit and thermal protection. Operating Region and Power Dissipation The maximum power dissipation of RT9181 depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. The power dissipation across the device is P = IOUT (VIN
- VOUT)
The GND pin of the RT9181 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. Capacitor Selection and Regulator Stability Like any low-dropout regulator, the external capacitors used with the RT9181 must be carefully selected for regulator stability and performance. Using a capacitor whose value is 1F on the RT9181 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 to a clean analog ground.
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RT9181
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 must meet both requirements for minimum amount of capacitance and ESR in all LDO applications. The RT9181 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 with ESR is > 5m on the RT9181 output ensures stability. The RT9181 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 load-transient response, stability, and PSRR. The output capacitor should be located not more than 0.5" from the VOUT pin of the RT9181 and returned to 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 low-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 manufacturer. Load-Transient Considerations The RT9181 load-transient response graphs show 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 and ESL of the output capacitor. Increasing the output capacitor's value and decreasing the ESR and ESL attenuates the overshoot. Reverse Current Path The power transistor used in the RT9181 has an inherent diode connected between each regulator input and output (see Figure 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 Figure 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 damage to the part.
Figure 1
VIN
VOUT
Figure 2
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RT9181
Outline Dimension
H D L C B
b A A1 e
Symbol A A1 B b C D e H L
Dimensions In Millimeters Min 0.889 0.000 1.397 0.356 2.591 2.692 0.838 0.080 0.300 Max 1.295 0.152 1.803 0.559 2.997 3.099 1.041 0.254 0.610
Dimensions In Inches Min 0.035 0.000 0.055 0.014 0.102 0.106 0.033 0.003 0.012 Max 0.051 0.006 0.071 0.022 0.118 0.122 0.041 0.010 0.024
SOT-23-5 Surface Mount Package
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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