Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - system monitor Dual voltage detector SSOP 16

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LTC2901

2901fb

Programmable Quad Supply

Monitor with Adjustable Reset

and Watchdog Timers

■

Simultaneously Monitors Four Supplies

■

16 User Selectable Combinations of 5V, 3.3V, 3V,

2.5V, 1.8V, 1.5V and/or ±Adj Voltage Thresholds

■

Guaranteed Threshold Accuracy: ±1.5% of

Monitored Voltage Over Temperature

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Selectable Supply Tolerance: 5% and 10% Below

Monitored Voltage (LTC2901-3/LTC2901-4)

■

Low Supply Current: 43μA Typ

■

Adjustable Reset Time

■

Adjustable Watchdog Time

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Open-Drain RST Output (LTC2901-1/LTC2901-3)

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Push-Pull RST Output (LTC2901-2/LTC2901-4)

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Individual Nondelayed Monitor Output for Each Supply

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Power Supply Glitch Immunity

■

Guaranteed RST for V

CC

≥ 1V

■

16-Lead Narrow SSOP Package

The LTC

®

2901 is a programmable supply monitor for

systems with up to four supply voltages. One of 16 preset

or adjustable voltage monitor combinations can be se-

lected using an external resistor divider connected to the

program pin. The preset voltage thresholds are accurate

to ±1.5% over temperature. All four voltage comparator

outputs are connected to separate pins for individual

supply monitoring.

The reset and watchdog delay times are adjustable using

external capacitors. Tight voltage threshold accuracy and

glitch immunity ensure reliable reset operation without

false triggering. The RST output is guaranteed to be in the

correct state for V

CC

down to 1V. The LTC2901-1/

LTC2901-3

features an open-drain RST output, while the

LTC2901-2/

LTC2901-4

has a push-pull RST output.

The 43μA supply current makes the LTC2901 ideal for

power conscious systems and it may be configured to

monitor less than four inputs. The parts are available in

the 16-lead narrow SSOP package.

Quadruple Supply Monitor (5V, 3.3V, 2.5V, 1.8V)

■

Desktop and Notebook Computers

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Multivoltage Systems

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Telecom Equipment

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Portable Battery-Powered Equipment

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Network Servers

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

V1

V2

V

REF

V

PG

COMP1

COMP2

COMP3

COMP4

WDI

WDO

RST

GND

R1

59k

1%

R3

10k

POWER

GOOD

R2

40.2k

1%

C

WT

47nF

C

RT

47nF

C2

0.1μF

C1

0.1μF

V4V3

LTC2901-2

CWTCRT

t

RST

= 216ms

t

WD

= 940ms

2901 TA01

DC/DC

CONVERTER

1.8V

2.5V

3.3V

5V

SYSTEM

LOGIC

DESCRIPTIO

U

FEATURES

APPLICATIO S

U

TYPICAL APPLICATIO

U

Quadruple Supply Monitor (5V, 3.3V, 2.5V, 1.8V)

10% Undervoltage Monitoring, Watchdog Asserts RST

V1

V2

V

REF

V

PG

COMP1

COMP2

COMP3

COMP4

WDI

TOL

RST

GND

R1

59k

1%

R3

10k

POWER

GOOD

R2

40.2k

1%

C

WT

47nF

5V

C

RT

47nF

C2

0.1μF

C1

0.1μF

V4V3

LTC2901-4

CWTCRT

t

RST

= 216ms

t

WD

= 940ms

2901 TA01b

DC/DC

CONVERTER

1.8V

2.5V

3.3V

5V

SYSTEM

LOGIC

Patent Pending.

Summary of content (16 pages)

PAGE 1
LTC2901 Programmable Quad Supply Monitor with Adjustable Reset and Watchdog Timers U FEATURES DESCRIPTIO ■ The LTC®2901 is a programmable supply monitor for systems with up to four supply voltages. One of 16 preset or adjustable voltage monitor combinations can be selected using an external resistor divider connected to the program pin. The preset voltage thresholds are accurate to ±1.5% over temperature.
PAGE 2
LTC2901 W W W AXI U U ABSOLUTE RATI GS (Notes 1, 2, 3) V1, V2, V3, V4, VPG ..................................... – 0.3V to 7V RST (LTC2901-1/LTC2901-3) ..................... – 0.3V to 7V RST (LTC2901-2/LTC2901-4) ....... – 0.3V to (V2 + 0.3V) COMPX ....................................................... – 0.3V to 7V CWT, WDI, WDO ......................................... – 0.3V to 7V VREF, CRT, TOL ............................ – 0.3V to (VCC + 0.3V) Reference Load Current (IVREF) ...................
PAGE 3
LTC2901 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted.
PAGE 4
LTC2901 TEST CIRCUITS V1 V2 V3 V4 RST, WDO LTC2901-1 OR COMPX LTC2901-3 V1 V2 V3 V4 ISOURCE 1μA LTC2901-1 LTC2901-3 RST, WDO OR COMPX 2901 F01 V1 V2 V3 V4 ISINK 2.5mA, 100μA LTC2901-2 RST LTC2901-4 ISOURCE 200μA 2901 F02 Figure 1. RST, WDO, COMPX VOH Test 2901 F03 Figure 2. RST, WDO, COMPX VOL Test Figure 3. Active Pull-Up RST VOH Test W UW TI I G DIAGRA S VX Monitor Timing VX VRTX tRST tUV 1.
PAGE 5
LTC2901 U W TYPICAL PERFOR A CE CHARACTERISTICS 5V Threshold Voltage vs Temperature 3.3V Threshold Voltage vs Temperature THESHOLD VOLTAGE, VRT50 (V) 4.725 4.700 4.675 4.650 4.625 3.135 2.850 3.125 2.840 THRESHOLD VOLTAGE, VRT30 (V) THRESHOLD VOLTAGE, VRT33 (V) 4.750 3V Threshold Voltage vs Temperature 3.115 3.105 3.095 3.085 3.075 3.065 3.055 3.035 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 2901 G01 2.810 2.800 2.790 2.780 80 2.
PAGE 6
LTC2901 U W TYPICAL PERFOR A CE CHARACTERISTICS IV1 vs Temperature IV2 vs Temperature IV3 vs Temperature 1.5 1.1 V1 = 5V 1.4 V2 = 3.3V V3 = 2.5V 1.3 V4 = 1.8V 1.2 V1 = 5V 1.0 V2 = 3.3V V3 = 2.5V 0.9 V4 = 1.8V 0.8 60 1.1 0.7 50 40 IV3 (μA) V1 = 5V 90 V2 = 3.3V V3 = 2.5V 80 V4 = 1.8V 70 IV2 (μA) 1.0 0.9 0.4 20 0.7 0.3 10 0.6 0.2 0.5 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 IV4 vs Temperature 0.5 0.4 0.3 0.2 0.
PAGE 7
LTC2901 U W TYPICAL PERFOR A CE CHARACTERISTICS Reset Time-Out Period vs Capacitance Watchdog Time-Out Period vs Capacitance 10 TA = 25°C 10 1 10m 1m 10p 100p 10n 1n CWT (FARAD) 100n 1μ ISINK (mA) 10m 1m 100p 100n 10n 1n CRT (FARAD) 3.0 – 40°C VOH (V) VOL (V) V1 = 5V V2 = 3V V3 = 2.5V V4 = 1V 0.5 2.0 – 40°C 1.5 25°C 70 80 90 20 0.5 2 1 1.5 ISOURCE (mA) 1.5 2 2.5 3 3.5 V2 (V) 4 4.
PAGE 8
LTC2901 U U U PI FU CTIO S COMP3 (Pin 1): Comparator Output 3. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V3 is above reset threshold. May be pulled greater than V2 using external pull-up. COMP1 (Pin 2): Comparator Output 1. Nondelayed, active high logic output with weak pull-up to V2. Pulls high when V1 is above reset threshold. May be pulled greater than V2 using external pull-up. V3 (Pin 3): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V or ADJ.
PAGE 9
LTC2901 W BLOCK DIAGRA LTC2901-1/LTC2901-2 V1 V2 POWER DETECT VCC 6μA COMP1 – V2 2 + V2 – V1 4 V2 14 V3 6μA + COMP2 16 RESISTIVE DIVIDER MATRIX 3 – V4 13 + V2 6μA GND 10 COMP3 – + VPG 11 1 A/D V2 BUFFER 6μA VREF 12 BANDGAP REFERENCE COMP4 15 ADJUSTABLE RESET PULSE GENERATOR VCC V2 LTC2901-1 2μA 6μA 22μA RST 6 LTC2901-2 V2 10μA TRANSITION DETECT VCC WATCHDOG TIMER RST 6 VCC 2μA 6μA 22μA 5 CRT CRT 8 V2 WDO WDI 7 9 CWT CWT 2901 DB-1 2901fb 9
PAGE 10
LTC2901 W BLOCK DIAGRA LTC2901-3/LTC2901-4 V1 V2 POWER DETECT VCC 6μA COMP1 – V2 2 + V2 – V1 4 V2 14 V3 6μA + COMP2 16 RESISTIVE DIVIDER MATRIX 3 – V4 13 + V2 6μA GND 10 COMP3 – + VPG 11 1 A/D V2 BUFFER 6μA VREF BANDGAP REFERENCE 12 COMP4 15 ADJUSTABLE RESET PULSE GENERATOR BUFFER GAIN ADJUST TOL VCC V2 LTC2901-3 2μA 7 6μA 22μA RST 6 LTC2901-4 V2 10μA TRANSITION DETECT VCC WATCHDOG TIMER RST 6 VCC 2μA 22μA 5 CRT CRT 8 WDI 9 CWT CWT 2901 DB-1 2901fb 10
PAGE 11
LTC2901 U W U U APPLICATIO S I FOR ATIO Power-Up The greater of V1, V2 is the internal supply voltage (VCC). On power-up, VCC will power the drive circuits for the RST and the COMPX pins. This ensures that the RST and COMPX outputs will be low as soon as V1 or V2 reaches 1V. The RST and COMPX outputs will remain low until the part is programmed. After programming, if any one of the VX inputs is below its programmed threshold, RST will be a logic low.
PAGE 12
LTC2901 U W U U APPLICATIO S I FOR ATIO VTRIP Table 2. Suggested 1% Resistor Values for the ADJ Inputs LTC2901 R3 1% + V3 OR V4 R4 1% – + – 0.5V 2901 F05 Figure 5. Setting the Positive Adjustable Trip Point 12 R4 1% VREF 13 V4 R3 1% LTC2901 – + VTRIP VSUPPLY (V) VTRIP (V) R3 (kΩ) R4 (kΩ) 12 11.25 2150 100 10 9.4 1780 100 8 7.5 1400 100 7.5 7 1300 100 6 5.6 1020 100 5 4.725 845 100 3.3 3.055 511 100 3 2.82 464 100 2.5 2.325 365 100 1.8 1.
PAGE 13
LTC2901 U W U U APPLICATIO S I FOR ATIO Pull-Up Current vs V2 curve). Output rise time (10% to 90%) is estimated using: tRISE ≈ 2.2 • RPU • CLOAD where RPU is the on-resistance of the pull-up transistor. The on-resistance as a function of the V2 voltage at room temperature is estimated using: RPU = 6 • 105 Ω V2 – 1 with V2 = 3.3V, RPU is about 260k. Using 150pF for load capacitance, the rise time is 86μs.
PAGE 14
LTC2901 U W U U APPLICATIO S I FOR ATIO Monitoring Power Supply Controller Activity Figure 7 demonstrates how the LTC2901 can be used to monitor switcher activity. The monitor is configured to supervise 3.3V, 2.5V, 1.8V and one adjustable input. Because 2.5V does not exist in this application, the V2 input is tied to the V1 (3.3V) input. The feedback voltage on the LTC1772 (0.8V typ) is monitored with the adjustable input (V4). The RST pin will go high 216ms (CRT = 47nF) after the 3.3V and 1.
PAGE 15
LTC2901 U TYPICAL APPLICATIO S Quad Supply Monitor with Watchdog Timer Disabled 5V, 3V, 1.8V, 12V (ADJ) 1 2 1.8V 5V 3 4 5 SYSTEM RESET 6 7 8 CRT COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2901 V4 CRT VREF RST VPG WDO GND WDI CWT 5V, –5V Monitor with Watchdog Timer Disabled and Unused V2, V3 Inputs Pulled Above Trip Thresholds 16 1 15 14 2 R3 2.15M 1% 3V 13 3 12V VTRIP = 11.
PAGE 16
LTC2901 U TYPICAL APPLICATIO Monitor Seven Supplies (12V, 5V, 3.3V, 2.5V, 1.8V, –2V, –5.2V) with Sequenced Reset and AC Present Indication 5V 12V 5V 3.3V 2.5V 1.8V –2V –5.2V AC/DC DC/DC CONVERTERS 10k 0.1μF 4 14 3.3V 3 1.8V 13 8 120V AC 12 LOW VOLTAGE SECONDARY 11 121k 16.2k 1% 1% 10 LTC2901-1 2 V1 COMP1 16 V2 COMP2 1 V3 COMP3 15 V4 COMP4 6 WDI RST 7 VREF WDO 5 CRT VPG 9 CWT GND 10k 4 5V MONITOR 0.1μF 3.3V MONITOR 2.5V 14 3 1.8V MONITOR 13 –5.2V MONITOR 8 12 12V 487k 86.