Datasheet

UNISONIC TECHNOLOGIES CO., LTD
L1923
Preliminary
CMOS IC
500mA HIGH PSRR LDO
REGULATORS
„
DESCRIPTION
The UTC L1923 is a low supply current, low dropout linear regulator.
It is operating at 2.5V - 5.5V. The supply current is as low as 55μA in
the no–load condition. In the shutdown mode, the maximum supply
current is less than 1μA.
A built-in over-temperature protection circuit is designed to protect
the device from being damaged by thermal overload. The over-current
protection limit is set at 800mA (TYP.)
The UTC L1923 can be operated on the following two modes. When
the SET pin is connected to ground, the output of L1923 is a pre-set
value and the external components are not needed to decide the
output voltage. When an output other than the preset value is needed,
two external resistors should be used as voltage dividers and then the
output voltage is decided by the resistor ratio.
The UTC L1923 is generally used in notebook computers, cellular
phones, PDAs, digital still camera and video recorders and other
hand-held devices.
„
FEATURES
* Low No-Load Supply Current: 90µA
* Guaranteed 500mA Output Current
* Dropout Voltage is 200mV @ 250mA Load
*OTP(Over-Temperature Protection) and Short-Circuit Protection
* Two Modes Of Operation:
Fixed Mode:3.3V,3.5V,3.9V
Adjustable Mode: 1.25V - 5.5V
* Maximum Supply Current In Shutdown Mode is Less than 1µA
* Low Output Noise at 238µVRMS
* Stability with Lost Cost Ceramic Capacitors
„
ORDERING INFORMATION
Note:
Ordering Number
Lead Free
Halogen Free
L1923L-xx-AF5-R
L1923G-xx-AF5-R
xx: Output Voltage, refer to Marking Information.
www.unisonic.com.tw
Copyright © 2011 Unisonic Technologies Co., Ltd
Package
Packing
SOT-25
Tape Reel
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L1923
Preliminary
MARKING INFORMATION
„
PACKAGE
VOLTAGE CODE
33:3.3V
39:3.9V
5
4
BQ
1
G
2
3
G: Halogen Free
L: Lead Free
Voltage Code
PIN CONFIGURATION
SET
5
„
MARKING
35:3.5V
SOT-25
„
CMOS IC
OUT
4
1
2
3
SHDN
GND
IN
PIN DESCRIPTION
PIN NO.
PIN NAME
1
SHDN
2
GND
3
IN
4
OUT
5
SET
DESCRIPTION
Active-Low Shutdown Input. A logic low reduces the supply current to less than 1µA.
Connect to IN for normal operation.
Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board
ground plane to maximize thermal dissipation.
Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with 1µF to
GND
Regulator Output. Fixed or adjustable from 1.25V to +5.5V. Sources up to 500mA.
Bypass with a 4.7µF, <0.2Ω typical ESR capacitor to GND.
Feedback Input for Setting the Output Voltage. Connect to GND to set the output
voltage to the preset output voltage. Connect to an external resistor divider for
adjustable-output operation.
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L1923
„
Preliminary
CMOS IC
BLOCK DIAGRAM
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L1923
„
Preliminary
CMOS IC
ABSOLUTE MAXIMUM RATING
PARAMETER
SYMBOL
RATINGS
UNIT
VIN to GND
-0.3~7
V
Output Short-Circuit Duration
Infinite
SET to GND
-0.3~7
V
SHDN to GND
-0.3~7
V
SHDN to IN
-7~0.3
V
OUT to GND
-0.3~(VIN+0.3)
V
Power Dissipation (TA=25°C)
PD
520
mW
Junction Temperature
TJ
150
°C
Operating Temperature
TOPR
-40~85
°C
Storage Temperature
TSTG
-65~160
°C
Notes: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
„
THERMAL DATA
PARAMETER
Junction to Ambient
„
SYMBOL
θJA
RATINGS
240
UNIT
°C/W
ELECTRICAL CHARACTERISTICS
(VIN =+3.6V, VSHDN =VIN, TA =TJ =+25°C, unless otherwise specified.) (Note 1)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP MAX UNIT
Input Voltage (Note 2)
VIN
2.5
5.5
V
Output Voltage Accuracy
VOUT Variation from specified VOUT, IOUT=1mA
-2
2
%
Adjustable Output Voltage
VOUT (Note 3)
VSET
5.5
V
Maximum Output Current
500
mA
Current Limit (Note 4)
ILIMIT
600
800
mA
Short Circuit Current
Isc
120
mA
Ground Pin Current
IQ
90
120
µA
200
IOUT=250mA
mV
Dropout Voltage (Note 5)
VDROP
IOUT=500mA
400
500
SET=GND, VIN=V(STD)+0.1V~5.5V,
Line Regulation
ΔVLNR
0.06 0.12
%/V
IOUT=10mA
Load Regulation
ΔVLDR IOUT= 10mA ~500mA
0.02
0.1
%/mA
Ripple Rejection
PSRR F=100Hz, 0.45VP-P, IOUT=10mA
65
dB
F≤100kHz, IOUT =0A
136
µV
Output Noise
Noise F≤100kHz, IOUT =250mA
238
(RMS)
F≤100kHz, IOUT =500mA
253
SHUTDOWN
VIH
Regulator enabled
1.5
SHDN Input Threshold
V
VIL
Regulator shutdown
0.4
SHDN Input Bias Current
ISHDN VSHDN= VIN
TA= +25°C
0.003 0.1
µA
Shutdown Supply Current
IQSHDN VOUT= 0V
TA= +25°C
0.2
1
µA
SET INPUT
TA= +25°C
1.225 1.25 1.275
VIN= 2.5V ~ 5.5V,
V
SET Reference Voltage (Note 3)
VSET
IOUT= 1mA
TA= TMIN to TMAX
1.25
SET Input Leakage Current
ISET
VSET= 1.3V (Note 3) TA= +25°C
5
30
nA
THERMAL PROTECTION
Thermal Shutdown Temperature TSHDN
145
°C
Thermal Shutdown Hysteresis ΔTSHDN
25
°C
Notes: 1.Limits is 100% production tested at TA= +25°C. Low duty pulse techniques are used during test to maintain
junction temperature as close to ambient as possible.
2.Guaranteed by line regulation test.
3.Adjustable mode only.
4.Not tested. For design purposes, the current limit should be considered 600mA minimum to 800mA
maximum.
5.The dropout voltage is defined as (VIN-VOUT) when VOUT is 100mV below the target value of VOUT.
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L1923
„
Preliminary
CMOS IC
APPLICATION INFORMATION
The UTC L1923 contains an error amplifier, 1.25V bandgap reference, PMOS output transistor, internal feedback
voltage divider, mode comparator, shutdown logic, over current protection circuit, and over temperature protection
circuit as shown in the block diagram.
The process of operation is like this: the mode comparator compares the voltage of SET pin with a pre-set voltage
reference of 0.35V. If the voltage of SET pin is smaller than 0.35V, the internal feedback voltage divider’s central tap
is connected to the error amplifier’s non-inverting input. Then, the error amplifier compares non-inverting input with
the 1.25V bandgap voltage reference. If the feedback voltage is larger than the voltage reference 1.25V, the error
amplifier’s output becomes higher. This makes the PMOS output transistor’s VGS (gate-to-source voltage) smaller, in
that condition, the current carrying capability of the PMOS output transistor is reduced, as a result the output voltage
decreases until the feedback voltage becomes equal to 1.25V. Similarly, when the feedback voltage is less than
1.25V, the error amplifier causes the output PMOS to conductor more current to pull the feedback voltage up to
1.25V. Thus, through this feedback action, the error amplifier, output PMOS, and the voltage dividers effectively form
a unity-gain amplifier with the feedback voltage force to be the same as the 1.25V bandgap reference.
The output voltage, VOUT, can be calculated as follows:
VOUT = 1.25 (1 + R1/R2).
(1)
Alternatively, the relationship between R1 and R2 is expressed in the following:
R1 = R2 (VOUT /1.25 - 1).
(2)
In order to reduce power dissipation and loop stability, it is recommended that R2 is 100KΩ. For UTC L1923-330,
R1 is 164K, and the pre-set VOUT is 3.30V.
In Figure 2, the SET pin voltage will be larger than 350mV when external voltage divider functions in the operation.
The non-inverting input of the amplifier will be connected to the external voltage divider. The conditions of equations
1 and 2 are still true since the operation of the feedback loop is the same. Equation 1 still presents the output
voltage.
Over Current Protection
To monitor the output current, the UTC L1923 applies a current mirror. A portion of the PMOS output transistor’s
current is mirrored to a resistor such that the voltage across this resistor is proportional to the output current. Once
the output current exceeds limit threshold, UTC L1923 would be protected with a limited output current. Further more,
when the output is short to ground, the output current would be folded-back to a less limit.
Over Temperature Protection
Over-temperature protection circuit is designed to prevent this device from being damaged due to abnormal
temperature during operation. It is used to turn off the output MOSFET if the temperature is higher than 145°C, the
switch does not turn on until the temperature drops to 120°C.
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L1923
„
Preliminary
CMOS IC
APPLICATION INFORMATION (Cont.)
Shutdown Mode
The UTC L1923 enters shutdown mode if the SHDN pin is applied to a logic low voltage. Under the shutdown
state, all the analog circuits are turned off completely, which reduces the current consumption to only the leakage
current. The UTC L1923 output pass transistor would get into high impedance level. There is an internal discharge
path to help to shorten discharge delay time.
Operating Region and Power Dissipation
The UTC L1923 is a linear regulator, so the power dissipation can be expressed by: P = IOUT (VIN – VOUT). And the
maximum power dissipation is calculated by:
PD(MAX) = (TJ–TA)/θJA,=(150°C -25°C)/240°C/W= 520mW
(Where (TJ–TA) is the temperature difference the die and the ambient air; θJA, is the thermal resistance of the
chosen package to the ambient air.)
For surface mount device, heat sinking is accomplished by using the heat spreading capabilities of the PC board
and its copper traces. The die attachment area of the UTC L1923’s lead frame is connected to pin 2, which is the
GND pin. Therefore, the GND pin of UTC L1923 can carry away the heat of the UTC L1923 die very effectively.
Connecting the GND pin to ground using a large ground plane near the GND pin can improve the power
consumption.
Capacitor Selection and Regulator Stability
A 1µF capacitor on the input and a 4.7µF capacitor on the output are recommended for most applications of the U
TC L1923. To get a better supply-noise rejection and transient response, input capacitors with larger values and
lower ESR are needed. A higher-value input capacitor (10µF) may be necessary if large, fast transients are
anticipated and the device is located several inches from the power source.
Power-Supply Rejection and Operation from Sources Other than Batteries
The UTC L1923 is particularly designed to deliver low dropout voltages and low quiescent currents in batterypowered systems. Power-supply rejection is 42dB at low frequencies. As the frequency increases above 20kHz, the
output capacitor is the major contributor to the rejection of power-supply noise.
When operating from sources other than batteries, improve supply-noise rejection and transient response by
increasing the values of the input and output capacitors, and using passive filtering techniques.
Input-Output (Dropout) Voltage
The minimum input-output voltage differential (or dropout voltage) of a regulator determines the lowest usable
supply voltage. In battery-powered system applications, this will determine the useful end-of-life battery voltage.
Because the UTC L1923 use a P-channel MOSFET pass transistor, their dropout voltage is a function of RDS(ON)
multiplied by the load current.
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L1923
„
Preliminary
CMOS IC
TYPICAL APPLICATION CIRCUIT
OUT
SHDN
OUTPUT
UTC
L1923
IN
+
BATTERY
-
COUT
4.7µ
SET
CIN
1µ
GND
Fixed Mode
OUT
SHDN
UTC
L1923
IN
+
BATTERY
-
CIN
1µ
OUTPUT
R1
SET
GND
COUT
4.7µ
R2
Adjustable Mode
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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www.unisonic.com.tw
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