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Si91871
New Product
Vishay Siliconix
300-mA Ultra Low-Noise LDO Regulator With Discharge Option
FEATURES
D D D D D D D D D D D D D Ultra Low Dropout--300 mV at 300-mA Load Ultra Low Noise--30 mVRMS (10-Hz to 100-kHz) Shutdown Control 130-mA Ground Current at 300-mA Load 1.5% Guaranteed Output Voltage Accuracy 400-mA Peak Output Current Capability Uses Low ESR Ceramic Capacitors Fast Start-Up (50 ms) Fast Line and Load Transient Response (v 30 ms) 1-mA Maximum Shutdown Current Output Current Limit Reverse Battery Protection Built-in Short Circuit and Thermal Protection D Output, Auto-Discharge In Shutdown Mode D Fixed 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.6, 2.7, 2.8, 2.85, 2.9, 3.0, 3.3, 3.5, 3.6, 5.0-V Output Voltage Options D MLP33-5 PowerPAKt Package
APPLICATIONS
D Cellular Phones, Wireless Handsets D Noise-Sensitive Electronic Systems, Laptop and Palmtop Computers D PDAs D Pagers D Digital Cameras D MP3 Player D Wireless Modem
DESCRIPTION
The Si91871 is a 300-mA CMOS LDO (low dropout) voltage regulator. It is the perfect choice for low voltage, low power applications. An ultra low ground current makes this part attractive for battery operated power systems. The Si91871 also offers ultra low dropout voltage to prolong battery life in portable electronics. Systems requiring a quiet voltage source, such as RF applications, will benefit from the Si91871's ultra low output noise. An external noise bypass capacitor connected to the device's BP pin can further reduce the noise level. The Si91871 is designed to maintain regulation while delivering 400-mA peak current, making it ideal for systems that have a high surge current upon turn-on. For better transient response and regulation, an active pull-down circuit is built into the Si91871 to clamp the output voltage when it rises beyond normal regulation. The Si91871 automatically discharges the output voltage by connecting the output to ground through a 100-W n-channel MOSFET when the device is put in shutdown mode. The Si91871 features reverse battery protection to limit reverse current flow to approximately 1-mA in the event reversed battery is applied at the input, thus preventing damage to the IC. The Si91871 is available in the 5-pin MLP33 PowerPAK package and is specified to operate over the industrial temperature range of -40_C to 85_
TYPICAL APPLICATION CIRCUIT
Si91871
VIN 2.2 mF SD SD VIN VOUT VOUT 2.2 mF
GND
BP 10 nF
MLP33-5
Document Number: 72012 S-03156--Rev. B, 03-Feb-03
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Si91871
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings Input Voltage, VIN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 6.0 to 6.5 V VSD (See Detailed Description) . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.3 V to VIN Output Current, IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . Short Circuit Protected Output Voltage, VOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.3 V to VIN + 0.3 V Package Power Dissipation, (Pd)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 W Thermal Resistance (qJA)a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55_C/W R(qJA)a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8_C/W Maximum Junction Temperature, TJ(max) . . . . . . . . . . . . . . . . . . . . . . . 150_C Storage Temperature, TSTG . . . . . . . . . . . . . . . . . . . . . . . . . . - 65_C to 150_C Notes a. Device mounted with all leads soldered or welded to PC board. b. Derate 20 mW/_C above TA = 25_C
New Product
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and 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 affect device reliability. Input Voltage, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 V to 6 V Input Voltage, VSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to VIN Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 300 mA CIN, COUTa (Ceramic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 mF CEB (Ceramic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01 mF Operating Ambient Temperature, TA . . . . . . . . . . . . . . . . . . . . - 40_C to 85_C Operating Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . - 40_C to 125_C Notes a. Maximum ESR of COUT: 0.2 W.
SPECIFICATIONS
Test Conditions Unless Specified
TA = 25_C, VIN = VOUT(nom) + 1 V IOUT = 1 mA, CIN = 2 mF, COUT = 2.0 mF VSD = 1.5 V
Limits
- 40 to 85_C
Parameter
Symbol
Tempa
Room Full
Minb
Typc
Maxb
Unit
Start-Up BP Current Input Voltage Range
IOUT VIN
ON/OFF = High
1 2 - 2.0 - 3.0 - 2.5 - 3.5 - 0.06 0 0 1 45 50 300 80 90 350 415 65 100 120 400 520 570 100 150 180 130 200 330 110 170 200 150 225 275 400 1 1 1 1 6 2.0 3.0 2.5 3.5 0.18 0.3 0.4
mA V
VOUT w 1.8 V Output Voltage Accuracy 1 mA v IOUT v 300 mA VOUT = 1.2 V Line Regulation (VOUT v 3 V) Line Regulation (3.0 V < VOUT v3.6 V) Line Regulation (5-V Version) DVOUT DVIN 100 From VIN = VOUT(nom) + 1 V to VOUT(nom) + 2 V
Room Full Room Full Full Full
%
VOUT(nom) From VIN = 5.5 V to 6 V IOUT = 1 mA
%/V
Full Room Room
Dropout Voltaged, g (VOUT(nom) w 2.6 V) VIN - VOUT Dropout Voltaged, g (VOUT(nom) t 2.6 V, VIN w 2 V)
IOUT = 50 mA IOUT = 300 mA IOUT = 50 mA IOUT = 300 mA IOUT = 0 mA
Full Room Full Room Full Room Full Room
mV
Ground Pin (VOUT(nom) v 3 V)
Currente, g IOUT = 300 mA IGND IOUT = 0 mA
Full Room Full Room Full Room
mA m
Ground Pin Currente (VOUT(nom) u 3 V) IOUT = 300 mA Peak Output current www.vishay.com IO(peak) VOUT w 0.95 x VOUT(nom). tPW = 2 ms
Full Full
mA Document Number: 72012 S-03156--Rev. B, 03-Feb-03
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Si91871
New Product
SPECIFICATIONS
Test Conditions Unless Specified
TA = 25_C, VIN = VOUT(nom) + 1 V IOUT = 1 mA, CIN = 2 mF, COUT = 2.0 mF VSD = 1.5 V
Vishay Siliconix
Limits
- 40 to 85_C
Parameter
Symbol
Tempa
Minb
Typc
Maxb
Unit
Output Noise Voltage
eN
VNOM = 2.6 V, BW = 10 Hz to 100 kHz, 0 mA t IOUT t 300 mA, CNOISE = 0.01 mF f = 1 kHz f = 10 kHz f = 100 kHz
Room Room Room Room Room Room Room Room
30 60 40 30 20
mV(rms)
Ripple Rejection
DVOUT/DVIN
IOUT = 300 mA
dB
Dynamic Line Regulation Dynamic Load Regulation Thermal Shutdown Junction Temperature Thermal Hysteresis Reverse current Short Circuit Current
DVO(line) DVO(load) TJ(S/D) THYST IR ISC
VIN : VOUT(nom) + 1 V to VOUT(nom) + 2 V tr/tf = 2 ms, IOUT = 300 mA IOUT : 1 mA to 300 mA, tr/tf = 2 ms
mV 20 150 20 1 700 mA mA _C C
VIN = - 6.0 V VOUT = 0 V
Room Room
Shutdown
Shutdown Supply Current SD Pin Input Voltage Auto Discharge Resistance SD Pin Input Currentf SD Hysteresis VOUT Turn-On Time ICC(off) VSD R_DIS IIN(SD) VHYST(SD) tON VSD (See Figure 1), ILOAD = 100 nA VSD = 1.5 V, VIN = 6 V VSD = 0 V High = Regulator ON (Rising) Low = Regulator OFF (Falling) Room Full Full Room Room Full 100 0.7 150 50 1.5 0.1 1 VIN 0.4 mA V W mA mV ms
Notes a. Room = 25_C, Full = - 40 to 85_C. b. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum. c. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing. Typical values for dropout voltage at VOUT w 2 V are measured at VOUT = 3.3 V, while typical values for dropout voltage at VOUT < 2 V are measured at VOUT = 1.8 V. d. Dropout voltage is defined as the input to output differential voltage at which the output voltage drops 2% below the output voltage measured with a 1-V differential, provided that VIN does not not drop below 2.0 V. e. Ground current is specified for normal operation as well as "drop-out" operation. f. The device's shutdown pin includes a typical 2-MW internal pull-down resistor connected to ground. g. VOUT(nom) is VOUT when measured with a 1-V differential to VIN.
TIMING WAVEFORMS
VIN VSD tr v 1 ms 0V
tON VNOM 0.95 VNOM
VOUT
FIGURE 1. Timing Diagram for Power-Up
Document Number: 72012 S-03156--Rev. B, 03-Feb-03 www.vishay.com
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Si91871
Vishay Siliconix
PIN CONFIGURATION
New Product
MLP33-5 PowerPAK
SD BP VIN VOUT 2
1
GND GND 5 5 GND GND
1 2 3 4
3 4
Top View Bottom View
PIN DESCRIPTION
Pin Number
1 2 3 4 5
Name
SD BP VIN VOUT GND
Function
By applying less than 0.4 V to this pin, the device will be turned off. Connect this pin to VIN if unused Noise bypass pin. For low noise applications, a 0.01 mF ceramic capacitor should be connected from this pin to ground. Input supply pin. Bypass this pin with a 1-mF ceramic or tantalum capacitor to ground Output voltage. Connect COUT between this pin and ground. Ground pin. For better thermal capability, directly connected to large ground plane
ORDERING INFORMATION
Part Number
SI91871DMP-12-T1 Si91871DMP-15-T1 Si91871DMP-18-T1 Si91871DMP-20-T1 Si91871DMP-22-T1 Si91871DMP-25-T1 Si91871DMP-26-T1 Si91871DMP-27-T1 Si91871DMP-28-T1 Si91871DMP-285-T1 Si91871DMP-29-T1 Si91871DMP-30-T1 Si91871DMP-33-T1 Si91871DMP-35-T1 Si91871DMP-36-T1 Si91871DMP-50-T1
Marking
7112 7115 7118 7120 7122 7125 7126 7127 7128 71285 7129 7130 7133 7135 7136 7150
Voltage
1.2 1.5 1.8 2.0 2.2 2.5 2.6 2.7 2.8 2.85 2.9 3.0 3.3 3.5 3.6 5.0
Temp. Range
Pkg.
- 40 to 85_C _
MLP33-5
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Document Number: 72012 S-03156--Rev. B, 03-Feb-03
Si91871
New Product
Vishay Siliconix
TYPICAL CHARACTERISTICS (INTERNALLY REGULATED, 25_C UNLESS NOTED)
Normalized Output Voltage vs. Load Current
0.30 VIN = VOUT(nom) + 1 V 0.15 0.00 - 0.15 - 0.30 - 0.45 - 0.60 - 0.75 0 50 100 150 200 250 300 Load Current (mA) V OUT (%) 0.2 IOUT = 0 mA Output Voltage (%) - 0.0 IOUT = 75 mA - 0.2 IOUT = 150 mA - 0.4 IOUT = 300 mA - 0.6 - 0.8 - 1.0 - 40 0.4 VIN = VOUT(nom) + 1 V
Normalized VOUT vs. Temperature
- 15
10
35
60
85
Ambient Temperature (_C)
GND Current vs. Load Current
150 VOUT = 3.0 V VIN = 4.0 V 125 25_C I GND ( mA) I GND ( mA) 200 85_C 250 300
No Load GND Pin Current vs. Input Voltage
100 - 40_C
150 85_C 25_C 100 - 40_C
75 50
50 0 50 100 150 200 250 300 Load Current (mA)
0 2 3 4 5 6 7 Input Voltage (V)
Power Supply Rejection
0 CIN = 1 mF COUT = 1 mF ILOAD = 150 mA VOUT = 3.0 V I SC (mA) 750
Output Short Circuit Current vs. Temperature
VOUT = 2.6 V 725
- 20
700 Gain (dB)
- 40
675
650 - 60 625
- 80 10 100 1000 10000 100000 1000000 Frequency (Hz)
600 - 40
- 15
10
35
60
85
AmbientTemperature (_C)
Document Number: 72012 S-03156--Rev. B, 03-Feb-03
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Si91871
Vishay Siliconix
New Product
TYPICAL CHARACTERISTICS (INTERNALLY REGULATED, 25_C UNLESS NOTED)
Dropout Voltage vs. Load Current
350 VOUT = 3.0 V 300 250 V DROP (mV) 2.0 200 150 100 50 0 0 60 120 180 240 300 ILOAD (mA) 0.5 V OUT (V) 2.5 3.0 VOUT = 3.0 V
VIN - VOUT Transfer Characteristic
1.5
1.0
0.0 0 1 2 3 VIN (V) 4 5 6
Dropout Voltage vs. Temperature
350 VOUT = 3.0 V 300 IOUT = 300 mA Dropout Voltage (mV) 250 V DROP (mV) 200 150 100 50 0 - 50 IOUT = 10 mA IOUT = 0 mA - 25 0 25 50 75 100 125 150 Junction Temperature (_C) IOUT = 150 mA 300 250 200 150 350 400
Dropout Voltage vs. VOUT
IOUT = 300 mA
IOUT = 75 mA 100 50 0 1.0
IOUT = 150 mA
IOUT = 75 mA
IOUT = 10 mA 1.5 2.0 2.5 3.0 VOUT 3.5 4.0 4.5 5.0
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Document Number: 72012 S-03156--Rev. B, 03-Feb-03
Si91871
New Product
TYPICAL WAVEFORMS
Vishay Siliconix
Load Transient Response-1
Load Transient Response-2
VOUT 10 mV/div VOUT 10 mV/div
ILOAD 100 mA/div
ILOAD 100 mA/div
20 ms/div VOUT = 3.0 V COUT = 1 mF ILOAD = 1 to 150 mA trise = 2 msec
20 ms/div VOUT = 3.0 V COUT = 1 mF ILOAD = 150 to 1 mA tfall = 2 msec
LineTransient Response-1
LineTransient Respons-2
VOUT 10 mV/div VOUT 10 mV/div
VIN 2 V/div
VIN 2 V/div
20 ms/div VINSTEP = 4 to 5 V VOUT = 3 V COUT = 1 mF CIN = 1 mF ILOAD = 150 mA trise = 5 msec
20 ms/div VINSTEP = 5 to 4 V VOUT = 3 V COUT = 1 mF CIN = 1 mF ILOAD = 150 mA tfall = 5 msec
Document Number: 72012 S-03156--Rev. B, 03-Feb-03
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Si91871
Vishay Siliconix
TYPICAL WAVEFORMS
New Product
Output Noise
10
Noise Spectrum
VOUT 200 mV/div
Output Spectral Noise Density
mV
Hz
0.01 4 ms/div VIN = 4 V VOUT = 3 V IOUT = 150 mA CNOISE = 0.01 mF BW = 10 Hz to 100 kHz 10 Hz VIN = 4 V VOUT = 3 V ILOAD = 150 mA CNOISE = 0.01 mF 1 MHz
FUNCTIONAL BLOCK DIAGRAM
Si91871
VIN Reverse Polarity Protection BP Reference +
VOUT Thermal Sensor
Current Limit
SD
Shutdown Control
GND
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Document Number: 72012 S-03156--Rev. B, 03-Feb-03
Si91871
New Product
DETAILED DESCRIPTION
The Si91871 is a low-noise, low drop-out and low quiescent current linear voltage regulator, packaged in a small footprint MLP33-5 package. The Si91871 can supply loads up to 300 mA. As shown in the block diagram, the circuit consists of a bandgap reference error, amplifier, p-channel pass transistor and feedback resistor string. An external bypass capacitor connected to the BP pin reduces noise at the output. Additional blocks, not shown in the block diagram, include a precise current limiter, reverse battery and current protection and thermal sensor. Thermal Overload Protection The thermal overload protection limits the total power dissipation and protects the device from being damaged. When the junction temperature exceeds 150_C, the device turns the p-channel pass transistor off. Reverse Battery Protection The Si91871 has a battery reverse protection circuitry that disconnects the internal circuitry when VIN drops below the GND voltage. There is no current drawn in such an event. When the SD pin is hardwired to VIN, the user must connect the SD pin to VIN via a 100-kW resistor if reverse battery protection is desired. Hardwiring the SD pin directly to the VIN pin is allowed when reverse battery protection is not desired. Noise Reduction An external 10-nF bypass capacitor at BP is used to create a low pass filter for noise reduction. The start-up time is fast, since a power-on circuit pre-charges the bypass capacitor. After the power-up sequence the pre-charge circuit is switched to standby mode in order to save current. It is therefore not recommended to use larger bypass capacitor values than 50 nF. When the circuit is used without a capacitor, stable operation is guaranteed. Auto-Discharge The Si91871 VOUT has an internal 100-W (typ.) discharge path to ground when the SD pin is low.
I OUT (A) 0.30 0.25 TA = 50_C TA = 70_C
Vishay Siliconix
Junction temperature is in turn dependent on power dissipation in the pass device, the thermal resistance of the package and the circuit board, and the ambient temperature. The power dissipation is defined as PD = (VIN - VOUT) * IOUT . Junction temperature is defined as TJ = TA + ((PD * (RJC + RCA)). To calculate the limits of performance, these equations must be rewritten. Allowable power dissipation is calculated using the equation PD = (TJ - TA )/ (RJC + RCA) While allowable output current is calculated using the equation IOUT = (TJ - TA )/ (RJC + RCA) * (VIN - VOUT). Ratings of the Si91871 that must be observed are TJmax = 125 _C, TAmax = 85 _C, (VIN - VOUT)max = 5.3 V, RJC = 8 _C/W. The value of RCA is dependent on the PC board used. The value of RCA for the board used in device characterization is approximately 46 _C/W. Figure 1 shows the performance limits graphically for the Si91871 mounted on the circuit board used for thermal characterization.
0.35
Stability The circuit is stable with only a small output capacitor equal to 6 nF/mA (= 2 mF @ 300 mA). Since the bandwidth of the error amplifier is around 1 -3 MHz and the dominant pole is at the output node, the capacitor should be capacitive in this range, i.e., for 150-mA load current, an ESR <0.2 W is necessary. Parasitic inductance of about 10 nH can be tolerated. Safe Operating Area The ability of the Si91871 to supply current is ultimately dependent on the junction temperature of the pass device.
Document Number: 72012 S-03156--Rev. B, 03-Feb-03
0.20 0.15 0.10 0.05 (VIN - VOUT)MAX = 5.3 V 0.00 0 1 2 3 VIN - VOUT (V) 4 5
TA = 85_C
6
Figure 1. Safe Operating Area
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