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LT1175

1175ff

TYPICAL APPLICATION

FEATURES DESCRIPTION

500mA Negative

Low Dropout Micropower

Regulator

The LT

1175 is a negative micropower low dropout

regulator. It features 45μA quiescent current, dropping

to 10μA in shutdown. A new reference ampliﬁ er topology

gives precision DC characteristics along with the ability to

maintain good loop stability with an extremely wide range

of output capacitors. Very low dropout voltage and high

efﬁ ciency are obtained with a unique power transistor

anti-saturation design. Adjustable and ﬁ xed 5V versions

are available.

Several new features make the LT1175 very user-friendly.

The SHDN pin can interface directly to either positive or

negative logic levels. Current limit is user-selectable at

200mA, 400mA, 600mA and 800mA. The output can be

forced to reverse voltage without damage or latchup. Un-

like some earlier designs, the increase in quiescent current

during a dropout condition is actively limited.

The LT1175 has complete blowout protection with current

limiting, power limiting and thermal shutdown. Special

attention was given to the problem of high temperature

operation with micropower operating currents,

preventing

output voltage rise under no-load conditions. The LT1175

is available in 8-pin PDIP and SO packages, 3-lead SOT-

223 as well as 5-pin surface mount DD and through-hole

TO-220 packages. The 8-pin SO package is specially

constructed for low thermal resistance.

Typical LT1175 Connection

APPLICATIONS

Operating Current: 45μA

Adjustable Current Limit

Low Voltage Linear Dropout Characteristics

Stable with Wide Range of Output Capacitors

Shutdown Current: 10μA

Positive or Negative Shutdown Logic

Fixed 5V and Adjustable Versions

Tolerates Reverse Output Voltage

Available in 8-pin PDIP and SO Packages, 3-lead

SOT-223, 5-Pin Surface Mount DD and Through-Hole

TO-220 Packages

Analog Systems

Modems

Instrumentation

A/D and D/A Converters

Interface Drivers

Battery-Powered Systems

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Minimum Input-to-Output Voltage

IS NEEDED ONLY IF REGULATOR IS MORE THAN 6" FROM

INPUT SUPPLY CAPACITOR. SEE APPLICATIONS INFORMATION

SECTION FOR DETAILS

OUT

≥ 0.1μF

–5V

UP TO 500mA

–V

SHDN GND

LT1175-5

SENSE

OUTPUT

1175 TA01

LIM4

LIM2

+ +

OUTPUT CURRENT (A)

INPUT-TO-OUTPUT VOLTAGE (V)

1.0

0.8

0.6

0.4

0.2

0.4

0.5

1175 TA02

0.1

0.3

0.6

0.7

= 25°C

LIM2

, I

LIM4

TIED TO V

Summary of content (20 pages)

PAGE 1
LT1175 500mA Negative Low Dropout Micropower Regulator DESCRIPTION FEATURES n n n n n n n n n Operating Current: 45μA Adjustable Current Limit Low Voltage Linear Dropout Characteristics Stable with Wide Range of Output Capacitors Shutdown Current: 10μA Positive or Negative Shutdown Logic Fixed 5V and Adjustable Versions Tolerates Reverse Output Voltage Available in 8-pin PDIP and SO Packages, 3-lead SOT-223, 5-Pin Surface Mount DD and Through-Hole TO-220 Packages APPLICATIONS n n n n n n Analog Systems
PAGE 2
LT1175 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage (Transient 1 sec, Note 12) ...................25V Input Voltage (Continuous) .......................................20V Input-to-Output Differential Voltage (Note 13) ..........20V 5V SENSE Pin (with Respect to GND Pin) ......... 2V, –10V ADJ SENSE Pin (with Respect to OUTPUT Pin)...................20V, –0.5V 5V SENSE Pin (with Respect to OUTPUT Pin)......................20V, –7V Output Reverse Voltage ..............................................
PAGE 3
LT1175 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1175CN8#PBF LT1175CN8#TRPBF LT1175CN8 8-Lead Plastic Dip 0°C to 125°C LT1175CN8-5#PBF LT1175CN8-5#TRPBF LT1175CN8-5 8-Lead Plastic Dip 0°C to 125°C LT1175CS8#PBF LT1175CS8#TRPBF 1175 8-Lead Plastic SO 0°C to 125°C LT1175CS8-5#PBF LT1175CS8-5#TRPBF 11755 8-Lead Plastic SO 0°C to 125°C LT1175CST-5#PBF LT1175CST-5#TRPBF 11755 3-Lead Plastic SOT-223 0°C to 125°C LT1175CQ#PB
PAGE 4
LT1175 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1175IT LT1175IT#TR LT1175IT 5-Lead Plastic TO-220 –40°C to 125°C LT1175IT-5 LT1175IT-5#TR LT1175IT-5 5-Lead Plastic TO-220 –40°C to 125°C LT1175MPS8 LT1175MPS8#TR 1175MP 8-Lead Plastic SO –55°C to 125°C LT1175MPS8-5 LT1175MPS8-5#TR 175MP5 8-Lead Plastic SO –55°C to 125°C LT1175MPQ LT1175MPQ#TR LT1175MPQ 5-Lead Plastic DD-Pak –55°C to 125°C LT1175MPQ-5 LT1175MPQ-5#TR L
PAGE 5
LT1175 ELECTRICAL CHARACTERISTICS The l denotes speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VOUT = 5V, VIN = 7V, IOUT = 0, VSHDN = 3V, ILIM2 and ILIM4 tied to VIN. To avoid confusion with “min” and “max” as applied to negative voltages, all voltages are shown as absolute values except where polarity is not obvious.
PAGE 6
LT1175 TYPICAL PERFORMANCE CHARACTERISTICS Typical Current Limit Characteristics Guaranteed Current Limit CURRENT LIMIT CHANGES ONLY SLIGHTLY WITH TEMPERATURE SO CURVES ARE REPRESENTATIVE OF ALL TEMPERATURES 0.8 5.05 ILIM2, ILIM4 TIED TO VIN 0.5 CURRENT (A) ILIM2, ILIM4 TIED TO VIN CURRENT (A) Output Voltage Temperature Drift 0.6 0.6 ILIM4 TIED TO VIN 0.4 ILIM2 TIED TO VIN ILIM4 TIED TO VIN 0.4 0.3 CURVES REPRESENT MINIMUM GUARANTEED LIMITS AT ALL TEMPERATURES OUTPUT FIXED 5V PART 5.
PAGE 7
LT1175 TYPICAL PERFORMANCE CHARACTERISTICS Shutdown Input Current 15 POSITIVE THRESHOLD THRESHOLD (V) 15 TJ = 25°C TJ = 125°C 10 TJ = –55°C 10 PIN CURRENT (μA) 2.0 20 1.5 NEGATIVE THRESHOLD 1.0 0.5 5 5 VIN = 25V CHARACTERISTICS DO NOT CHANGE SIGNIFICANTLY WITH TEMPERATURE, SO A SINGLE CURVE IS SHOWN.
PAGE 8
LT1175 PIN FUNCTIONS (N8/Q/ST/S8/T) VIN (Pins 1, 8/Pin 3, Tab/Pin 2, Tab/Pins 1, 8/Pin 3, Tab): Power is supplied to the device through this pin. A bypass capacitor is required on this pin if the device is more than six inches away from the main ﬁlter capacitor. In general, the impedance of a battery rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits.
PAGE 9
LT1175 APPLICATIONS INFORMATION Note to Reader: To avoid confusion when working with negative voltages (is –6V more or less than –5V?), I have decided to treat the LT1175 as if it were a positive regulator and express all voltages as positive values, both in text and in formulas. If you do the same and simply add a negative sign to the eventual answer, confusion should be avoided. Please don’t give me a hard time about “preciseness” or “correctness.
PAGE 10
LT1175 APPLICATIONS INFORMATION normally a good thing when the regulator is used by itself, but it prevents the user from shutting down the regulator when a second power source is connected to the LT1175 output. If active output pull-down is needed in shutdown, it can be added externally with a depletion mode PFET as shown in Figure 2. Note that the maximum pinch-off voltage of the PFET must be less than the positive logic high level to ensure that the device is completely off when the regulator is active.
PAGE 11
LT1175 APPLICATIONS INFORMATION GND LT1175 + 3.8V R1 – COUT A1 LOAD + ESR R2 SENSE Q2 AC FEEDFORWARD PATH OUTPUT CF 20pF OUTPUT RC 0.5Ω NEGATIVE DC FEEDBACK AT LIGHT LOADS Q3 PARASITIC COLLECTOR RESISTANCE Q1 POWER TRANSISTOR RN RLIM CURRENT LIMIT SENSE RESISTOR 1175 F03 VIN Figure 3 This condition can occur with ceramic or ﬁlm capacitors which often have an ESR under 0.1Ω.
PAGE 12
LT1175 APPLICATIONS INFORMATION capacitors do not fail during a “shorting out” surge, only during a “charge up” surge. The output capacitor should be located within several inches of the regulator. If remote sensing is used, the output capacitor can be located at the remote sense node, but the GND pin of the regulator should also be connected to the remote site. The basic rule is to keep SENSE and GND pins close to the output capacitor, regardless of where it is.
PAGE 13
LT1175 APPLICATIONS INFORMATION TA = Maximum ambient temperature TMAX = Maximum LT1175 die temperature (125°C for commercial and industrial grades) θJA = LT1175 thermal resistance, junction to ambient VIN = Maximum continuous input voltage at maximum load current ILOAD = Maximum load current Example: LT1175S8 with ILOAD = 200mA, VOUT = 5V, VIN = 7V, TA = 60°C. Maximum die temperature for the LT1175S8 is 125°C. Thermal resistance from Table 2 is found to be 80°C/W. Die Temperature = 60 + 80 (0.
PAGE 14
LT1175 APPLICATIONS INFORMATION To estimate regulator output ripple under different conditions, the following general comments should be helpful: 1. Output ripple at high frequency is only weakly affected by load current or output capacitor size for medium to heavy loads. At very light loads (<10mA), higher frequency ripple may be reduced by using larger output capacitors. 2.
PAGE 15
LT1175 PACKAGE DESCRIPTION N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 8.255 +0.889 –0.381 ) .045 – .065 (1.143 – 1.651) .130 ± .005 (3.302 ± 0.127) .065 (1.651) TYP .100 (2.54) BSC .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 NOTE: 1.
PAGE 16
LT1175 PACKAGE DESCRIPTION Q Package 5-Lead Plastic DD Pak (Reference LTC DWG # 05-08-1461) .256 (6.502) .060 (1.524) TYP .060 (1.524) .390 – .415 (9.906 – 10.541) .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) 15° TYP .060 (1.524) .183 (4.648) +.008 .004 –.004 +0.203 0.102 –0.102 .059 (1.499) TYP .330 – .370 (8.382 – 9.398) ( ) .095 – .115 (2.413 – 2.921) .075 (1.905) .300 (7.620) +.012 .143 –.020 +0.305 3.632 –0.
PAGE 17
LT1175 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 7 8 .245 MIN 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) 2 .053 – .069 (1.346 – 1.752) .008 – .010 (0.203 – 0.254) NOTE: 1. DIMENSIONS IN 4 .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.
PAGE 18
LT1175 PACKAGE DESCRIPTION T Package 5-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1421) .390 – .415 (9.906 – 10.541) .165 – .180 (4.191 – 4.572) .147 – .155 (3.734 – 3.937) DIA .045 – .055 (1.143 – 1.397) .230 – .270 (5.842 – 6.858) .460 – .500 (11.684 – 12.700) .570 – .620 (14.478 – 15.748) .330 – .370 (8.382 – 9.398) .620 (15.75) TYP .700 – .728 (17.78 – 18.491) SEATING PLANE .152 – .202 .260 – .320 (3.861 – 5.131) (6.60 – 8.13) .095 – .115 (2.413 – 2.921) .155 – .195* (3.937 – 4.
PAGE 19
LT1175 REVISION HISTORY (Revision history begins at Rev E) REV DATE DESCRIPTION E 11/09 Revised Typical Application. PAGE NUMBER 1 Revised Pin Conﬁguration drawings and layout. 2 Updated Order Information. 3 VIN added and pin numbers added to Pin Functions. 7 Title added to Table 1. Revised Figures 1, 2, 3, 4a and 4b. Value correction in ﬁnal paragraph of the Output Capacitor section. F 7/10 8 8, 9, 10, 12 11 Added MP-grade.
PAGE 20
LT1175 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1121 150mA Positive Micropower Low Dropout Regulator with Shutdown SOT-223, 8-Lead SO, TO-92 Packages LT1129 700mA Positive Micropower Low Dropout Regulator with Shutdown DD-Pak, SOT-223, 8-Lead SO, TO-220, 20-Lead TSSOP Packages LT1185 3A Negative Low Dropout Regulator DD-Pak, TO-220 Packages LT1521 300mA Positive Micropower Low Dropout Regulator with Shutdown SOT-223, 8-Lead SO, 8-Lead MSOP Packages LT1529 3A Positive Micropower Low Dr