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FEATURES 1.2% Accuracy Over Line and Load Regulations @ 25 C Ultralow Dropout Voltage: 80 mV Typical @ 50 mA Requires Only C O = 0.47 F for Stability anyCAP = Stable with All Types of Capacitors (Including MLCC) Current and Thermal Limiting Low Noise Low Shutdown Current: 1 A 2.8 V to 12 V Supply Range -20 C to +85 C Ambient Temperature Range Several Fixed Voltage Options Ultrasmall SOT-23-5 Package Excellent Line and Load Regulations APPLICATIONS Cellular Telephones Notebook, Palmtop Computers Battery Powered Systems PCMCIA Regulator Bar Code Scanners Camcorders, Cameras GENERAL DESCRIPTION
anyCAP(R) 50 mA Low Dropout Linear Regulator ADP3308
FUNCTIONAL BLOCK DIAGRAM
Q1 THERMAL PROTECTION IN OUT
ADP3308
CC DRIVER gm R2 R1
ERR/NC Q2 SD
BANDGAP REF
GND
The ADP3308 is a member of the ADP330x family of precision low dropout anyCAP voltage regulators. It is pin-for-pin and functionally compatible with National's LP2980, but offers performance advantages. The ADP3308 stands out from the conventional LDOs with a novel architecture and an enhanced process. Its patented design requires only a 0.47 F output capacitor for stability. This device is stable with any type of capacitor regardless of its ESR (Equivalent Serial Resistance) value, including ceramic types for space restricted applications. The ADP3308 achieves 1.2% accuracy at room temperature and 2.2% overall accuracy over temperature, line and load regulations. The dropout voltage of the ADP3308 is only 80 mV (typical) at 50 mA. This device also includes a current limit and a shutdown feature. In shutdown mode, the ground current is reduced to ~1 A. The ADP3308 operates with a wide input voltage range from 2.8 V to 12 V and delivers a load current in excess of 100 mA. The ADP3308 anyCAP LDO offers a wide range of output voltages. For 100 mA version, refer to the ADP3309 data sheet.
ERR/NC 4
ADP3308-3.3
VIN C1 0.47 F 3 ON OFF SD GND 2 1 IN OUT 5 C2 0.47 F VOUT = +3.3V
Figure 1. Typical Application Circuit
anyCAP is a registered trademark of Analog Devices, Inc.
REV. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2000
ADP3308-xx-SPECIFICATIONS otherwise noted.) The following specifications apply to all voltage options.
1
(@ TA = -20 C to +85 C, VIN = 7 V, CIN = 0.47 F, COUT = 0.47 F, unless
Min Typ Max
Parameter OUTPUT VOLTAGE ACCURACY
Symbol VOUT
Conditions VIN = VOUTNOM + 0.3 V to 12 V IL = 0.1 mA to 50 mA TA = 25C VIN = VOUTNOM + 0.3 V to 12 V IL = 0.1 mA to 50 mA VIN = VOUTNOM + 0.3 V to 12 V TA = 25C IL = 0.1 mA to 50 mA TA = 25C IL = 50 mA IL = 0.1 mA VIN = 2.4 V IL = 0.1 mA VOUT = 98% of VOUTNOM IL = 50 mA IL = 10 mA IL = 1 mA ON OFF 0 < VSD 5 V 5 < VSD 12 V @ VIN = 12 V VSD = 0 V, VIN = 12 V TA = 25C VSD = 0 V, VIN = 12 V TA = 85C TA = 25C @ VIN = 12 V TA = 85C @ VIN = 12 V
Unit
-1.2 -2.2 0.02 0.06 0.54 0.19 0.9 0.08 0.025 0.004 2.0 0.75 0.75
+1.2 +2.2
% % mV/V mV/mA
LINE REGULATION LOAD REGULATION GROUND CURRENT GROUND CURRENT IN DROPOUT DROPOUT VOLTAGE
V O V IN
V O IL
IGND IGND VDROP
1.4 0.3 1.7 0.17 0.07 0.030 0.3 1 9
mA mA mA V V V V V A A A A A A A V mA V rms
SHUTDOWN THRESHOLD SHUTDOWN PIN INPUT CURRENT
VTHSD ISDIN
GROUND CURRENT IN SHUTDOWN IQ MODE
0.005 0.01
1 3 2 4 13
OUTPUT CURRENT IN SHUTDOWN MODE ERROR PIN OUTPUT LEAKAGE ERROR PIN OUTPUT "LOW" VOLTAGE PEAK LOAD CURRENT OUTPUT NOISE @ 5 V OUTPUT
IOSD IEL VEOL ILDPK VNOISE
ISINK = 400 A VIN = VOUTNOM + 1 V, TA = 25C f = 10 Hz-100 kHz
0.12 150 100
0.3
NOTES 1 Ambient temperature of 85C corresponds to a junction temperature of 125C under typical full load test conditions. Specifications subject to change without notice.
-2-
REV. B
ADP3308
ABSOLUTE MAXIMUM RATINGS* PIN FUNCTION DESCRIPTIONS
Input Supply Voltage . . . . . . . . . . . . . . . . . . . -0.3 V to +16 V Shutdown Input Voltage . . . . . . . . . . . . . . . . -0.3 V to +16 V Power Dissipation . . . . . . . . . . . . . . . . . . . Internally Limited Operating Ambient Temperature Range . . . -55C to +125C Operating Junction Temperature Range . . . -55C to +125C JA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165C/W JC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92C/W Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature Range (Soldering 10 sec) . . . . . . . . 300C Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C
*This is a stress rating only; operation beyond these limits can cause the device to be permanently damaged.
Pin Name 1 2 3 IN GND SD
Function Regulator Input. Ground Pin. Active Low Shutdown Pin. Connect to ground to disable the regulator output. When shutdown is not used, this pin should be connected to the input pin. Open Collector. Output that goes low to indicate the output is about to go out of regulation or no connect. Output of the Regulator, fixed 2.5, 2.7, 2.85, 2.9, 3.0, 3.3, or 3.6 volts output voltage. Bypass to ground with a 0.47 F or larger capacitor.
PIN CONFIGURATION
IN 1 5 OUT
4
ERR/NC
5
OUT
ORDERING GUIDE
Model ADP3308ART-2.5 ADP3308ART-2.7 ADP3308ART-2.85 ADP3308ART-2.9 ADP3308ART-3 ADP3308ART-3.3 ADP3308ART-3.6
Voltage Output 2.5 V 2.7 V 2.85 V 2.9 V 3.0 V 3.3 V 3.6 V
Package Option* SOT-23 SOT-23 SOT-23 SOT-23 SOT-23 SOT-23 SOT-23
Marking Code LAC DAC DJC DKC DCC DEC DFC
GND 2 SD
ADP3308
TOP VIEW 3 (Not to Scale) 4 ERR/NC
NC = NO CONNECT
*SOT = Surface Mount. Contact the factory for the availability of other output voltage options.
Other Member of anyCAP Family 1
Model ADP3309
Output Current 100 mA
Package Option2 SOT-23-5 Lead
NOTES 1 See individual data sheet for detailed ordering information. 2 SOT = Surface Mount.
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADP3308 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
REV. B
-3-
ADP3308-Typical Performance Characteristics
3.302 I L = 0mA 3.301
3.302 3.301
OUTPUT VOLTAGE - Volts
I L = 10mA
1150
OUTPUT VOLTAGE - Volts
VOUT = 3.3V VIN = 7V
GROUND CURRENT - A
VOUT = 3.3V I L = 0mA 900
3.300 3.299
3.300 3.299 3.298 3.297 3.296 3.295
650
VOUT = 3.3V 3.298 3.297 3.296 3.295 3.3 4 I L = 50mA
400
160
5
6 7 8 9 10 11 12 13 14 INPUT VOLTAGE - Volts
0
8
16 24 32 40 48 56 64 72 80 OUTPUT LOAD - mA
0
0
1.2 2.4 3.6 4.8 6.0 7.2 8.4 9.6 10.8 12.0 INPUT VOLTAGE - Volts
TPC 1. Line Regulation: Output Voltage vs. Supply Voltage
TPC 2. Output Voltage vs. Load Current
TPC 3. Quiescent Current vs. Supply Voltage
800
0.2 0.1 GROUND CURRENT - A
OUTPUT VOLTAGE - %
700 VIN = 7V 600
A
675
GROUND CURRENT -
0.0 -0.1 -0.2 I L = 30mA
I L = 0mA
500 400 300 200 100
IL = 50mA
550
425 IL = 0 TO 80mA 300
I L = 50mA -0.3 -0.4 -45 -25 -5
IL = 0mA
175
0
20 40 60 OUTPUT LOAD - mA
80
15 35 55 75 95 115 135 TEMPERATURE - C
0 -45 -25 -5
15 35 55 75 95 115 135 TEMPERATURE - C
TPC 4. Quiescent Current vs. Load Current
TPC 5. Output Voltage Variation % vs. Temperature
TPC 6. Quiescent Current vs. Temperature
120
5
INPUT/OUTPUT VOLTAGE - Volts
INPUT/OUTPUT VOLTAGE - Volts
INPUT/OUTPUT VOLTAGE - mV
VOUT = 3.3V RL = 66 4
8.0 VIN 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0 0 VSD = VIN CL = 0.47 F RL = 66 VOUT = 3.3V 20 40 60 80 100 120 140 160 180 200 TIME - s VOUT
96
72
3
48
2
24
1
0
0
20 40 60 OUTPUT LOAD - mA
80
0
0
1
3 2 4 3 2 INPUT VOLTAGE - Volts
1
0
TPC 7. Dropout Voltage vs. Output Current
TPC 8. Power-Up/Power-Down
TPC 9. Power-Up Overshoot
-4-
REV. B
ADP3308
3.320 3.310 3.300 3.290
Volts
3.320 VOUT = 3.3V 3.310
Volts
3.320
VOUT = 3.3V
3.310 3.300 3.290
VOUT = 3.3V CL = 0.47 F
3.300 3.290
Volts
3.280
RL = 66 CL = 0.47 F
3.280
RL = 3.3k CL = 0.47 F
3.280
VIN 7.5 7.0 7.5 7.0 0
VIN
mA
100 10
IOUT
0
40 80 120 160 200 240 280 320 360 400 TIME - s
20 40 60 80 100 120 140 160 180 200 TIME - s
0
100
200 300 TIME - s
400
500
TPC 10. Line Transient Response
TPC 11. Line Transient Response
TPC 12. Load Transient
Volts
3.320 3.310 VOUT = 3.3V CL = 4.7 F
3.3 0
VOUT = 3.3V
VOUT
4 CL = 0.47 F 3 3.3V 2 CL = 4.7 F VOUT
Volts
3.300
200 150
mA
3.280 100 IOUT
Volts
3.290
1 0 +3 0
100 50 0 0 1 2 3 TIME - s
IOUT
VOUT = 3.3V RL = 66
mA
VSD +3V
10
0
100
200 300 TIME - s
400
500
4
5
0
20
40 60 TIME - s
80
100
TPC 13. Load Transient
TPC 14. Short Circuit Current
TPC 15. Turn On
VOLTAGE NOISE SPECTRAL DENSITY - V/ Hz
4 3.3V 3 2 1 0 VOUT = 3.3V RL = 66 CL = 0.47 F
0 -10 a. 0.47 F, RL = 3.3k b. 0.47 F, RL = 66 c. 4.7 F, RL = 3.3k d. 4.7 F, RL = 66
VOUT = +3.3V b
10 VOUT = 3.3V CL = 0.47 F IL = 1mA 1
RIPPLE REJECTION - dB
-20 -30 -40 -50 -60 -70 -80 -90
Volts
a c
d
bd
0.1
3 0
VSD
0
20
40 60 TIME - s
80
100
-100 10
ac 100 1k 10k 100k FREQUENCY - Hz 1M 10M
0.01 100
10k 1k FREQUENCY - Hz
100k
TPC 16. Turn Off
TPC 17. Power Supply Ripple Rejection
TPC 18. Output Noise Density
REV. B
-5-
ADP3308
THEORY OF OPERATION
The new anyCAP LDO ADP3308 uses a single control loop for regulation and reference functions. The output voltage is sensed by a resistive voltage divider consisting of R1 and R2, which is varied to provide the available output voltage option. Feedback is taken from this network by way of a series diode (D1) and a second resistor divider (R3 and R4) to the input of an amplifier.
INPUT Q1 OUTPUT COMPENSATION CAPACITOR ATTENUATION (VBANDGAP /VOUT) gm PTAT VOS R4 R3 D1 (a) PTAT CURRENT R2 CLOAD
Additional features of the circuit include current limit and thermal shutdown. Compared to the standard solutions that give warning after the output has lost regulation, the ADP3308 provides improved system performance by enabling the ERR pin to give warning before the device loses regulation. As the chip's temperature rises above 165C, the circuit activates a soft thermal shutdown, indicated by a signal low on the ERR pin, to reduce the current to a safe level.
APPLICATION INFORMATION Capacitor Selection: anyCAP
R1 RLOAD
NONINVERTING WIDEBAND DRIVER
ADP3308
GND
Output Capacitors: as with any micropower device, output transient response is a function of the output capacitance. The ADP3308 is stable with a wide range of capacitor values, types and ESR (anyCAP). A capacitor as low as 0.47 F is all that is needed for stability. However, larger capacitors can be used if high output current surges are anticipated. The ADP3308 is stable with extremely low ESR capacitors (ESR 0), such as multilayer ceramic capacitors (MLCC) or OSCON. Input Bypass Capacitor: an input bypass capacitor is not required. However, for applications where the input source is high impedance or far from the input pin, a bypass capacitor is recommended. Connecting a 0.47 F capacitor from the input pin (Pin 1) to ground reduces the circuit's sensitivity to PC board layout. If a bigger output capacitor is used, the input capacitor must be 1 F minimum.
Thermal Overload Protection
Figure 2. Functional Block Diagram
A very high gain error amplifier is used to control this loop. The amplifier is constructed in such a way that at equilibrium it produces a large, temperature proportional input "offset voltage" that is repeatable and very well controlled. The temperature proportional offset voltage is combined with the complementary diode voltage to form a "virtual bandgap" voltage, implicit in the network, although it never appears explicitly in the circuit. Ultimately, this patented design makes it possible to control the loop with only one amplifier. This technique also improves the noise characteristics of the amplifier by providing more flexibility on the tradeoff of noise sources that leads to a low noise design. The R1, R2 divider is chosen in the same ratio as the bandgap voltage to the output voltage. Although the R1, R2 resistor divider is loaded by the diode D1 and a second divider consisting of R3 and R4, the values can be chosen to produce a temperature stable output. This unique arrangement specifically corrects for the loading of the divider so that the error resulting from base current loading in conventional circuits is avoided. The patented amplifier controls a new and unique noninverting driver that drives the pass transistor, Q1. The use of this special noninverting driver enables the frequency compensation to include the load capacitor in a pole splitting arrangement to achieve reduced sensitivity to the value, type and ESR of the load capacitance. Most LDOs place very strict requirements on the range of ESR values for the output capacitor because they are difficult to stabilize due to the uncertainty of load capacitance and resistance. Moreover, the ESR value required to keep conventional LDOs stable, changes, depending on load and temperature. These ESR limitations make designing with LDOs more difficult because of their unclear specifications and extreme variations over temperature. This is no longer true with the ADP3308 anyCAP LDO. It can be used with virtually any capacitor, with no constraint on the minimum ESR. This innovative design allows the circuit to be stable with just a small 0.47 F capacitor on the output. Additional advantages of the design scheme include superior line noise rejection and very high regulator gain which leads to excellent line and load regulation. An impressive 2.2% accuracy is guaranteed over line, load and temperature. -6-
The ADP3308 is protected against damage due to excessive power dissipation by its thermal overload protection circuit which limits the die temperature to a maximum of 165C. Under extreme conditions (i.e., high ambient temperature and power dissipation) where die temperature starts to rise above 165C, the output current is reduced until the die temperature has dropped to a safe level. The output current is restored when the die temperature is reduced. Current and thermal limit protections are intended to protect the device against accidental overload conditions. For normal operation, device power dissipation should be externally limited so that junction temperatures will not exceed 125C.
Calculating Junction Temperature
Device power dissipation is calculated as follows: PD = (VIN - VOUT) ILOAD + (VIN) IGND Where ILOAD and IGND are load current and ground current, VIN and VOUT are input and output voltages respectively. Assuming ILOAD = 50 mA, IGND = 2 mA, VIN = 5.5 V and VOUT = 2.7 V, device power dissipation is: PD = (5.5 - 2.7) 50 mA + 5.5 x 2 mA = 151 mW T = TJ - TA = PD x JA = 151 x 165 = 24.9C With a maximum junction temperature of 125C, this yields a maximum ambient temperature of ~100C.
Printed Circuit Board Layout Consideration
Surface mount components rely on the conductive traces or pads to transfer heat away from the device. Appropriate PC board layout techniques should be used to remove heat from the immediate vicinity of the package.
REV. B
ADP3308
The following general guidelines will be helpful when designing a board layout: 1. PC board traces with larger cross section areas will remove more heat. For optimum results, use PC boards with thicker copper and or wider traces. 2. Increase the surface area exposed to open air so heat can be removed by convection or forced air flow. 3. Do not use solder mask or silk screen on the heat dissipating traces because it will increase the junction to ambient thermal resistance of the package.
Shutdown Mode Higher Output Current
The ADP3308 can source up to 50 mA without any heatsink or pass transistor. If higher current is needed, an appropriate pass transistor can be used, as in Figure 4, to increase the output current to 1 A.
VIN = 4V TO 8V C1 47 F MJE253* R1 50 VOUT = 3.0V @ 1A
IN
OUT C2 10 F
ADP3308-3.0
SD GND
Applying a TTL high signal to the shutdown pin or tying it to the input pin will turn the output ON. Pulling the shutdown pin down to a TTL low signal or tying it to ground will turn the output OFF. In shutdown mode, quiescent current is reduced to less than 1 A.
APPLICATION CIRCUITS Crossover Switch
*AAVID531002 HEAT SINK IS USED
Figure 4. Higher Output Current Linear Regulator
Constant Dropout Post Regulator
The circuit in Figure 3 shows that two ADP3308s can be used to form a mixed supply voltage system. The output switches between two different levels selected by an external digital input. Output voltages can be any combination of voltages from the Ordering Guide of the data sheet.
VIN = 4V TO 12V IN OUT VOUT = 3.0V/3.3V
The circuit in Figure 5 provides high precision with low dropout for any regulated output voltage. It significantly reduces the ripple from a switching regulator while providing a constant dropout voltage, which limits the power dissipation of the LDO to 30 mW. The ADP3000 used in this circuit is a switching regulator in the step-up configuration.
ADP3308-3.0
OUTPUT SELECT
4V 0V
SD
GND
IN C1 1.0 F
OUT C2 0.47 F
ADP3308-3.3
SD GND
Figure 3. Crossover Switch
L1 6.8 H VIN = 2.5V TO 3.5V C1 100 F 10V D1 1N5817
ADP3308-3.0
IN OUT GND 3.0V@50mA C3 2.2 F SD
R1 120 ILIM VIN
C2 100 F 10V SW1 Q1 2N3906
R2 30.1k 1%
ADP3000-ADJ
FB GND SW2
Q2 2N3906 R3 124k 1% R4 274k
Figure 5. Constant Dropout Post Regulator
REV. B
-7-
ADP3308
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
5-Lead Surface Mount Package (SOT-23)
C00140b-.5-12/00 (rev. B)
0.022 (0.55) 0.014 (0.35) 0.122 (3.10) 0.106 (2.70)
0.071 (1.80) 0.059 (1.50) PIN 1
5 1 2
4 3
0.118 (3.00) 0.098 (2.50)
0.0374 (0.95) REF 0.075 (1.90) REF 0.051 (1.30) 0.035 (0.90) 0.006 (0.15) 0.000 (0.00) 0.020 (0.50) 0.010 (0.25) 0.057 (1.45) 0.035 (0.90) SEATING PLANE 10 0 0.009 (0.23) 0.003 (0.08)
-8-
REV. B
PRINTED IN U.S.A.

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