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Preliminary
RT9181
150mA LDO Regulator with POG
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 CE 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, Output 1.2V Up to 150mA Output Current Power Good (POG) Function Chip Enable/Shutdown Function Load Independent, Low Ground 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-25 Package
Pin Configurations
Part Number RT9181CB (Plastic SOT-25)
5 4
Pin Configurations
TOP VIEW
Applications
Processor Power-Up Sequencing Laptop, Notebook, and Palmtop Computers
1
2
3
1. 2. 3. 4. 5.
VIN GND CE POG VOUT
Ordering Information
RT9181 Package type B : SOT-25 Operating temperature range C: Commercial standard
Typical Application Circuit
10K VIN C IN 1F CE ON OFF VOUT GND VOUT C OUT 1F VIN POG POG
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RT9181
Pin Description
Pin Name VIN GND CE POG VOUT Input Pin Power Ground Pin Pin Function
Preliminary
Enable/Shutdown Input (Active High) Power Good Indicator Output Pin
Function Block Diagram
VIN CE Shutdown Control Thermal Sensor Gate Control Undervoltage Lockout Current Limit
Output Voltage Detection GOOD Delay Timer Fault POG Power Good Control GND
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2
_
Verf
VOUT
+
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Preliminary Absolute Maximum Ratings
Input Voltage, VIN CE Input Voltage Power Good Output Voltage Power Dissipation, PD @ TA = 25C SOT-25 Junction Temperature Range Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec.)
RT9181
7V 7V 7V 570mW -40C ~ 125C -65C ~ 150C 0C ~ 70C 260C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 1F, TA = 25C, unless otherwise specified) Parameter Input Voltage Range Output Voltage Accuracy Output Load Current Current Limit GND Current Line Regulation Load Regulation Dropout Voltage CE Input High Threshold CE Input Low Threshold CE Input Bias Current CE Supply Current VPOGH Power Good Low Threshold VPOGH Power Good High Threshold VOL Power Good Output Logic Low td(POG) Delay Time to Power Good Power Up Overshoot Thermal Shutdown Temperature Thermal Shutdown Hysteresis Output Voltage AC PSRR 100Hz, COUT = 1F, RLOAD = 100 TSD ILIMIT IG VLINE VDROP Symbol VIN VOUT IL = 25mA IL = 0.1mA, TA = 0C to 70C (Note) Continuous RLOAD = 1 No Load VIN = 3 to 5.5V, IOUT = 0.1mA IL = 150mA VIN = 3 to 5.5V VIN = 3 to 5.5V CE = GND or VIN CE = GND Output falls % of VOUT (power NOT timer (Power good)) Output reaches % of VOUT, start delay timer (power good) Fault condition, IOL = 100A See timing diagram Maximum voltage overshoot allowed on output during power-up Test Conditions Min 3 1.182 -2 150 160 90 -0.3 --2 ---85 --1 ----Typ -1.2 --300 160 --1 ---0.01 ---2 1 150 20 62 Max 5.5 1.218 +2 --250 +0.3 +3 --0.8 100 --90 0.4 5 ----Units V % mA mA A % % V V V nA A % % V mS % C C dB
VLOAD IL = 0.1mA to 150mA
Note: Assured by design, not tested in production
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RT9181
Typical Operating Charateristics
Output Voltage vs. Temperature
1.210
Preliminary
Output Voltage vs. Supply Voltage
1.210
Output Voltage (V)
1.200
Output Voltage (V)
VIN = 5V ILOAD = 0.1mA
-20 0 20 40 60 80
1.205
1.205
1.200
1.195
1.195
1.190
1.190 3.0 3.5 4.0 4.5
ILOAD = 0.1mA
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)
300
Current Limit (mA)
VIN = 5V
-20 0 20 40 60 80
350
350
300
250
250
200
200 3 3.5 4 4.5 5 5.5 6
Temperature ( C)
Supply Voltage (V)
Quiescent Current vs. Temperature
180 175 170 165 160 155 150 -20 0 20 40
Quiescent Current vs. Supply Voltage
180 175 170 165 160 155 150 3.0
Quiescent Current ( A)
VIN = 5V
60 80
Quiescent Current ( A)
3.5
4.0
4.5
5.0
5.5
6.0
Temperature ( C)
Supply Voltage (V)
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Preliminary
RT9181
POG Delay Time vs. Supply Voltage
POG Delay Time vs. Temperature
3.0 2.5 3.00 2.50
POG Delay Time (mS)
POG Delay Time (mS)
VIN = 5V
-20 0 40 Temperature ( C) 20 60 80
2.0 1.5 1.0 0.5 0.0
2.00 1.50 1.00 0.50 0.00 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Supply Voltage (V)
Under Voltage Lock Out
POG Response at Power Down
T
POG
1>
VIN
1>
T
1.2V VOUT VOUT
COUT = 1F
T T
2>
T T 1) Ch 1: 2) Ch 2: 2 Volt 5 ms 500 mVolt 5 ms
2>
1) Ch 1: 2) Ch 2:
5 Volt 25 us 500 mVolt 25 us
VIN = 5V COUT = 1F
Time
Time
POG Response vs. VOUT
T
POG
1>
2ms delay
T T
VOUT
2>
1) Ch 1: 2) Ch 2:
5 Volt 1 ms 500 mVolt 1 ms
VIN = 5V
Time
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RT9181
Timing Diagram
Preliminary
90% max of VOUT (normal) VPOGH t d(POG) 2.0ms typ. VOUT POG
VPOGL 85% min
Application Guides
CE/Shutdown The RT9181 is enabled by driving the CE input high, and shutdown by pulling the input low. If this feature is not to be used, the CE input should be tied to VIN to keep the regulator enabled at all times (the CE 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 2.0ms (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 POG 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 POG 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 150mA minimum. Thermal-overload protection limits total power dissipation in the RT9181. When the junction temperature exceeds TJ = +150C, 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 thermal-overload conditions. Thermal-overloaded protection is designed to protect the RT9181 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 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
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Preliminary
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. 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. in The RT9181 and is designed specifically to work with low ESR ceramic output capacitor space-saving 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 loadtransient 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, 2.2 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
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VIN
RT9181
sufficient for the application by the
large capacitor). If a tantalum capacitor is used at the input, it must be guaranteed to have a surge current rating manufacture. 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 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 damage to the part.
Fig. 1
VOUT
Fig. 2
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RT9181
Package Information
Preliminary
D
C
B
b
A e L
H
A1
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 0.102 0.356 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 0.004 0.014 Max 0.051 0.006 0.071 0.022 0.118 0.122 0.041 0.010 0.024
SOT- 25 Surface Mount Package
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Preliminary
RT9181
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RT9181
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
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