Datasheet

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LTC2909

2909fb

SEL Pin Connection for Input Polarity

Combinations

POLARITY

ADJ1 ADJ2 SEL PIN

+–

OPEN

––

GND

Precision Triple/Dual Input

UV, OV and Negative

Voltage Monitor

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Desktop and Notebook Computers

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Handheld Devices

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Network Servers

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Core, I/O Monitor

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Automotive

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Two Low Voltage Adjustable Inputs (0.5V)

■

Pin Selectable Input Polarity Allows Negative

and OV Monitoring

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Guaranteed Threshold Accuracy: ±1.5%

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6.5V Shunt Regulator for High Voltage Operation

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Low 50μA Quiescent Current

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Buffered 1V Reference for Negative Supply Offset

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Input Glitch Rejection

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Adjustable Reset Timeout Period

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Selectable Internal Timeout Saves Components

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Open-Drain

⎯

T Output

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Accurate UVLO for 2.5V, 3.3V, 5V Systems

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Ultralow Voltage Reset: V

= 0.5V Guaranteed

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Space Saving 8-Lead TSOT-23 and 3mm × 2mm DFN

Packages

3.3V UV/OV (Window) Monitor Application with

200ms Internal Timeout (3.3V Logic Out)

ADJ1

LTC2909-2.5

REF

ADJ2

RST

SEL

10k

FAULT

OUTPUT

2909 TA01a

453k

3.3V

10.7k

76.8k

BYP

100nF

TMR

GND

The LTC

2909 is a dual input monitor intended for a variety

of system monitoring applications. Polarity selection and

a buffered reference output allow the LTC2909 to monitor

positive and negative supplies for undervoltage (UV) and

overvoltage (OV) conditions.

The two inputs have a nominal 0.5V threshold, featuring

tight 1.5% threshold accuracy over the entire operating

temperature range. Glitch ﬁ ltering ensures reliable reset

operation without false triggering. A third ﬁ xed-threshold

UVLO monitor on the part’s V

(also 1.5% accuracy) is

available for standard logic supplies.

The common reset output has a timeout that may use

a preset 200ms, be set by an external capacitor or be

disabled. A three-state input pin sets the input polarity

of each adjustable input without requiring any external

components.

The LTC2909 provides a highly versatile, precise, space-

conscious, micropower solution for supply monitoring.

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Summary of content (16 pages)

PAGE 1
LTC2909 Precision Triple/Dual Input UV, OV and Negative Voltage Monitor U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Two Low Voltage Adjustable Inputs (0.5V) Pin Selectable Input Polarity Allows Negative and OV Monitoring Guaranteed Threshold Accuracy: ±1.5% 6.
PAGE 2
LTC2909 U W W W ABSOLUTE AXI U RATI GS (Notes 1, 2) Terminal Voltages VCC (Note 3)............................................. –0.3V to 6V SEL, ⎯R⎯S⎯T .............................................. –0.3V to 7.5V ADJ1, ADJ2 .......................................... –0.3V to 7.5V TMR ..........................................–0.3V to (VCC + 0.3V) Terminal Currents IVCC (Note 3) ....................................................±10mA IREF ..............................................................
PAGE 3
LTC2909 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = 2.5V (LTC2909-2.5), VCC = 3.3V (LTC2909-3.3), VCC = 5V (LTC2909-5), ADJ1 = ADJ2 = 0.55V, SEL = ﬂoating, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS VCC(MIN) Operating Supply Voltage ⎯R⎯S⎯T in Correct State ● MIN 0.5 VCC(SHUNT) VCC Shunt Regulation Voltage IVCC = 1mA, IVREF = 0 ● 6.0 ICC VCC Input Current 2.
PAGE 4
LTC2909 U W 506 504 502 500 498 496 494 492 –50 –25 0 50 75 25 TEMPERATURE (°C) 100 125 1.5 0.015 1.0 1.010 0.5 0 –0.5 –1.5 –50 –25 50 25 75 0 TEMPERATURE (°C) 1.015 TA = 125°C TA = –40°C TA = 25°C TA = –40°C 0.995 0.995 0.990 0.990 0.985 0.985 2 1 2.5 4.5 5 3 3.5 4 SUPPLY VOLTAGE, VCC (V) 5.5 Allowable Glitch Duration vs Magnitude RESET OCCURS ABOVE CURVE 200 100 0 0.1 1 10 100 GLITCH PERCENTAGE PAST THRESHOLD (%) 2909 G07 100 VCC = 5V VCC = 3.3V 45 40 VCC = 2.
PAGE 5
LTC2909 U W TYPICAL PERFOR A CE CHARACTERISTICS Shunt Regulation Voltage vs Supply Current 6.8 ICC = 10mA 6.6 ICC = 1mA ICC = 100μA 6.4 6.2 6.0 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 7.0 ⎯R⎯S⎯T Output Voltage vs VCC 5 TA = 25°C ADJ1 = 0.55 ADJ2 = 0.45 4 SEL = OPEN 10k PULL-UP R TO VCC 6.8 RST VOLTAGE (V) 7.0 SHUNT REGULATION VOLTAGE, VCC(SHUNT) (V) 6.6 6.4 2 LTC2909-2.5 LTC2909-3.3 0 6.0 0.01 0.
PAGE 6
LTC2909 U U U PI FU CTIO S (TSOT-23/DFN Package) ADJ1 (Pin 1/Pin 8): Adjustable Voltage Input 1. Input to voltage monitor comparator 1 (0.5V nominal threshold). The polarity of the input is selected by the state of the SEL pin (refer to Table 1). Tie to REF if unused (with SEL = VCC or Open). ADJ2 (Pin 2/Pin 7): Adjustable Voltage Input 2. Input to voltage monitor comparator 2 (0.5V nominal threshold). The polarity of the input is selected by the state of the SEL pin (refer to Table 1).
PAGE 7
LTC2909 W BLOCK DIAGRA SEL VCC VCC THREE-STATE DECODE CONTROL 2 ADJ1 6.5V CONTROL 1 + TMR – ADJ2 ADJUSTABLE PULSE GENERATOR + THREE-STATE DECODE RST GND 200ms PULSE GENERATOR – VCC + – + – SEL GND OPEN VCC 500mV + REF + – 1.
PAGE 8
LTC2909 U W U U APPLICATIO S I FOR ATIO The LTC2909 is a low power, high accuracy dual/triple supply monitor with two adjustable inputs and an accurate UVLO. Reset timeout may be selected with an external capacitor, set to an internally generated 200ms, or disabled entirely. The three-state polarity select pin (SEL) chooses one of three possible polarity combinations for the adjustable input thresholds, as described in Table 1.
PAGE 9
LTC2909 U U W U APPLICATIO S I FOR ATIO If the state of the SEL pin conﬁgures a given input as “negative polarity,” the voltage at the ADJx pin must be below the trip point (0.5V nominal), or the ⎯R⎯S⎯T output will be pulled low. Conversely, if a given input is conﬁgured as “positive polarity,” the pin voltage must be above the trip point or ⎯R⎯S⎯T will assert low.
PAGE 10
LTC2909 U U W U APPLICATIO S I FOR ATIO Table 2b. Possible Combinations of Supply Monitoring. For Example Purposes, All Supplies are Monitored at 5% Tolerance and Connections are Shown Only for ADJ1, ADJ2, REF, SEL SEL OPEN 15V (UV/OV) –15V (UV/OV) RP6 2.37M RN6 10.2M ADJ1 RP5 10.7k ADJ2 ADJ1 RN5 40.2k SEL ADJ2 REF REF 1 Negative UV and OV 1 Positive UV and OV –15V (OV) 15V (OV) 15V (UV) –15V (UV) RP2 3.09M RN2 10.2M RN2 3.09M RP2 6.
PAGE 11
LTC2909 U W U U APPLICATIO S I FOR ATIO The above discussion is concerned only with the DC value of the monitored supply. Real supplies also have relatively high frequency variation from sources such as load transients, noise and pickup. These variations should not be considered by the monitor in determining whether a supply voltage is valid or not. The variations may cause spurious outputs at ⎯R⎯S⎯T, particularly if the supply voltage is near its trip threshold.
PAGE 12
LTC2909 U U W U APPLICATIO S I FOR ATIO For a positive-monitoring application, RP2 is then chosen by: REF ADJ1 RP2 = RP1(2VTRIP – 1) For a negative-monitoring application: RN4 RN2 = RN1(1 – 2VTRIP) RN5 Note that the value VTRIP should be negative for a negative application. The LTC2909 can also be used to monitor a single supply for both UV and OV. This may be accomplished with three resistors, instead of the four required for two independent supplies. Conﬁgurations are shown in Figures 3 and 4.
PAGE 13
LTC2909 U W U U APPLICATIO S I FOR ATIO Table 3. Suggested Resistor Values for 5% Monitoring 5% UV NOMINAL RX1 VOLTAGE 24 232k 15 115k 12 49.9k 9 115k 5 137k 3.3 221k 2.5 115k 1.8 63.4k 1.5 59.0k 1.2 127k 1 200k –5 133k –9 97.6k –12 107k –15 107k Trip points are nominal voltage ±6.5%. 5% OV RX2 RX1 RX2 RX4 5% UV and OV RX5 10.2M 3.09M 1.07M 1.82M 1.15M 1.15M 422k 150k 107k 158k 174k 1.37M 1.74M 2.49M 3.09M 102k 200k 102k 78.7k 137k 340k 51.1k 115k 137k 102k 100k 118k 115k 40.2k 309k 5.11M 6.
PAGE 14
LTC2909 U U W U APPLICATIO S I FOR ATIO This imposes a practical limit of 1μF (9 second timeout) if the length of timeout during power-up needs to be longer than 200ms. If the power-up timeout is not important, larger capacitors may be used, subject to the limitation that the capacitor leakage current must not exceed 500nA, or the function of the timer will be impaired. pulled above VCC, providing the voltage limits of the pin are observed.
PAGE 15
LTC2909 U PACKAGE DESCRIPTIO DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702) 0.61 ±0.05 (2 SIDES) R = 0.115 TYP 5 0.56 ± 0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) 0.675 ±0.05 2.50 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.25 ± 0.05 4 0.25 ± 0.05 0.75 ±0.05 0.200 REF 0.50 BSC 2.20 ±0.05 (2 SIDES) 0.38 ± 0.10 8 (DDB8) DFN 1103 0.50 BSC 2.15 ±0.05 (2 SIDES) 0 – 0.
PAGE 16
LTC2909 U TYPICAL APPLICATIO Automotive Supply System with Overvoltage, Overcurrent and Overtemperature Protection and Undervoltage Reset DC/DC D1: 1N5238B OR SIMILAR Q1, Q2: FFB2227 OR SIMILAR VIN 12V DC/DC M1 IRLZ34 RS 0.01Ω RG2 10Ω 2N6507 3.3V SYSTEM CBYP3 100nF RL1 4.7k RCC 4.7k Q1 RP2A 2.49M RP2B 2.05M RP2C 221k RL2 100k RG1 1k RPU1 4.7k CBYP2 100nF VCC ADJ1 RST CG 10nF PWRGD LT1641-2 GND TIMER RP2E 1.15M LTC2909-2.5 RFB2 100k SEL VCC VCC ADJ1 RST LTC2909-2.