Datasheet

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LTC2902

2902f

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Programmable Quad Supply

Monitor with Adjustable Reset Timer

and Supply Tolerance

■

Simultaneously Monitors Four Supplies

■

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

2.5V, 1.8V, 1.5V and/or ±Adjustable Voltage

Thresholds

■

Guaranteed Threshold Accuracy: ±1.5% of Monitored

Voltage Over Temperature

■

Selectable Supply Tolerance: 5%, 7.5%,

10%, 12.5% Below Monitored Voltage

■

Low Supply Current: 43µA Typ

■

Adjustable Reset Time

■

RESET Disable Pin for Margining Applications

■

Open-Drain RST Output (LTC2902-1)

■

Push-Pull RST Output (LTC2902-2)

■

Individual Nondelayed Monitor Outputs for Each Supply

■

Power Supply Glitch Immunity

■

Guaranteed RESET for V

≥ 1V

The LTC

2902 is a programmable supply monitor for sys-

tems 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 pro-

gram pin. The preset voltage thresholds are digitally pro-

grammable to 5%, 7.5%, 10% or 12.5% below the nomi-

nal operating voltage, and are accurate to 1.5% over tem-

perature. All four voltage comparator outputs are con-

nected to separate pins for individual supply monitoring.

The reset delay time is adjustable using an external

capacitor. 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

down to 1V and may be disabled

during supply margin testing. The LTC2902-1 features

an open-drain RST output, while the LTC2902-2 has a

push-pull RST output.

The 43µA supply current makes the LTC2902 ideal for power

conscious systems and the part may be configured to

monitor less than four inputs. The LTC2902-1/LTC2902-2

are available in the 16-lead narrow SSOP package.

Quad Supply Monitor with Adjustable Tolerance (5V, 3.3V, 2.5V, 1.8V)

■

Desktop and Notebook Computers

■

Multivoltage Systems

■

Telecom Equipment

■

Portable Battery-Powered Equipment

■

Network Servers

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

REF

COMP1

COMP2

COMP3

COMP4

RST

RDIS

GND

59k

10k

POWER

GOOD

40.2k

133

47nF

0.1µF

V4V3

LTC2902-2

CRT

RST

= 216ms

MARGIN

TOLERANCE = 5%

2902 TA01

DC/DC

CONVERTER

1.8V

2.5V

3.3V

SYSTEM

LOGIC

Summary of content (16 pages)

PAGE 1
LTC2902 Programmable Quad Supply Monitor with Adjustable Reset Timer and Supply Tolerance DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Simultaneously Monitors Four Supplies 16 User Selectable Combinations of 5V, 3.3V, 3V, 2.5V, 1.8V, 1.5V and/or ±Adjustable Voltage Thresholds Guaranteed Threshold Accuracy: ±1.5% of Monitored Voltage Over Temperature Selectable Supply Tolerance: 5%, 7.5%, 10%, 12.
PAGE 2
LTC2902 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Notes 1, 2, 3) V1, V2, V3, V4, VPG ..................................... – 0.3V to 7V RST (LTC2902-1)........................................ – 0.3V to 7V RST (LTC2902-2).......................... – 0.3V to (V2 + 0.3V) COMPX, RDIS ............................................. – 0.3V to 7V T0, T1 .......................................... – 0.3V to (VCC + 0.3V) CRT ............................................. – 0.3V to (VCC + 0.
PAGE 3
LTC2902 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
LTC2902 TEST CIRCUITS V1 V2 V3 V4 RST LTC2902-1 OR COMPX LTC2902-1 V1 V2 V3 V4 ISOURCE 1µA V1 V2 V3 V4 ISINK 2.5mA, 100µA RST OR COMPX 2902 F02 2902 F01 Figure 1. RST, COMPX VOH Test LTC2902-2 RST ISOURCE 200µA 2902 F03 Figure 2. RST, COMPX VOL Test Figure 3. Active Pull-Up RST VOH Test WU W TI I G DIAGRA VX Monitor Timing VRTX VX tRST tUV 1.5V RST 2902 TD COMPX U W TYPICAL PERFOR A CE CHARACTERISTICS 3.3V Threshold Voltage vs Temperature 5V Threshold Voltage vs Temperature 3.
PAGE 5
LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS 2.5V Threshold Voltage vs Temperature 1.8V Threshold Voltage vs Temperature 1.710 THRESHOLD VOLTAGE, VRT25 (V) 2.350 THRESHOLD VOLTAGE, VRT18 (V) 5% 2.325 2.300 7.5% 2.275 2.250 10% 2.225 2.200 2.175 12.5% 2.150 2.125 2.100 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 1.425 5% 1.685 1.660 7.5% 1.635 1.610 10% 1.585 1.560 12.5% 1.535 1.510 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 100 2902 G04 80 1.305 12.5% 1.285 10% 0.473 0.
PAGE 6
LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS 0.6 0.5 0.4 0.3 0.2 0.1 0 – 60 –40 – 20 0 20 40 60 TEMPERATURE (°C) 80 100 TA = 25°C 400 350 RESET OCCURS ABOVE CURVE 300 250 200 150 100 50 0 0.1 1 10 100 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 3 2 1 0 120 100 80 60 40 20 0 1 10 100 0.1 RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VRTX) 2902 G25 Reset Time-Out Period vs Capacitance 10 CRT = 1500pF 8.4 (SILVER MICA) 7.9 7.4 6.4 5.9 5.4 4.9 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) 0.5 1.
PAGE 7
LTC2902 U W TYPICAL PERFOR A CE CHARACTERISTICS COMPX Propagation Delay vs Input Overdrive Above Threshold COMPX Pull-Up Current vs V2 (COMPX Held at 0V) 20 250 TA = 25°C COMPX PROPAGATION DELAY (µs) 18 PULL-UP CURRENT (µA) 16 14 12 10 8 6 4 2 0 1 1.5 2 2.5 4 3 3.5 V2 (V) 4.
PAGE 8
LTC2902 U U U PI FU CTIO S RST (Pin 6): Reset Logic Output. Active low with weak pull-up to V2 (LTC2902-1) or active pull-up to V2 (LTC2902-2). Pulls low when any voltage input is below the reset threshold and held low for programmed delay time after all voltage inputs are above threshold. May be pulled above V2 using an external pull-up (LTC2902-1 only). T0 (Pin 7): Digital Input for Supply Tolerance Selection (5%, 7.5%, 10% or 12.5%). Used in conjunction with T1 (Pin 9).
PAGE 9
LTC2902 W BLOCK DIAGRA 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 BUFFER GAIN ADJUST ADJUSTABLE RESET PULSE GENERATOR VCC V2 LTC2902-1 2µA 6µA 22µA RST 10µA 6 VCC 7 T0 9 T1 5 CRT 8 RDIS CRT LTC2902-2 V2 RST 6 2902 DB-1 2902f 9
PAGE 10
LTC2902 U W U U APPLICATIO S I FOR ATIO Power-Up On power-up, the larger of V1 or V2 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 11
LTC2902 U W U U APPLICATIO S I FOR ATIO Table 2. Suggested 1% Resistor Values for the ADJ Inputs VTRIP LTC2902 R3 1% + V3 OR V4 R4 1% – + – 0.5V 5% TOLERANCE MODE 2902 F05 Figure 5. Setting the Positive Adjustable Trip Point 12 R4 1% VREF 13 V4 R3 1% LTC2902 – + 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.
PAGE 12
LTC2902 U W U U APPLICATIO S I FOR ATIO particular output is known, output fall time (10% to 90%) is estimated using: tFALL ≈ 2.2 • RPD • CLOAD where RPD is the on-resistance of the internal pull-down transistor. The typical performance curve (VOL vs ISINK) demonstrates that the pull-down current is somewhat linear versus output voltage. Using the 25°C curve, RPD is estimated to be approximately 40Ω. Assuming a 150pF load capacitance, the fall time is about 13.2ns.
PAGE 13
LTC2902 U TYPICAL APPLICATIO S Quad Supply Monitor, 5% Tolerance 5V, 3V, 1.8V, 12V (ADJ) 1 2 1.8V 5V 3 4 5 SYSTEM RESET CRT 6 7 8 COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2902 V4 CRT VREF RST VPG T0 GND RDIS T1 16 15 14 3V 13 R3 2.15M 1% 12V VTRIP = 11.
PAGE 14
LTC2902 U TYPICAL APPLICATIO S Quad Supply Monitor with LED Undervoltage Indicators, 12.5% Tolerance, Reset Disabled 5V, 3.3V, 2.5V, 1.5V RL1 1k LED RL3 1k LED 1 2 2.5V 3 4 5V 5 6 7 CRT RL2 1k 8 LED COMP3 COMP2 COMP1 COMP4 V3 V2 V1 LTC2902 V4 CRT VREF RST VPG T0 GND RDIS T1 RL4 1k LED 16 15 14 3.3V 13 1.5V 12 R1 53.6k 1% 11 10 9 R2 47.
PAGE 15
LTC2902 U PACKAGE DESCRIPTIO GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 – .196* (4.801 – 4.978) .045 ±.005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 ± .0015 .150 – .157** (3.810 – 3.988) .0250 TYP RECOMMENDED SOLDER PAD LAYOUT 1 .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) 2 3 4 5 6 7 .053 – .068 (1.351 – 1.727) 8 .004 – .0098 (0.102 – 0.249) 0° – 8° TYP .016 – .050 (0.
PAGE 16
LTC2902 U TYPICAL APPLICATIO Quad Supply Monitor with Hysteresis 5% Tolerance (Supplies Rising) 12.5% Tolerance (After RST Goes High) 5V 4 3.3V 14 3 2.5V 1.8V 13 8 12 R1 59k 1% R2 40.2k 1% 11 10 LTC2902-1 2 COMP1 16 V2 COMP2 1 V3 COMP3 15 V4 COMP4 6 RDIS RST 7 VREF T0 9 T1 VPG 5 CRT GND V1 10k CRT 2902 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold LTC694-3.3 3.