LTC2908IDDB-A1#TRMPBF

LTC2908

Precision

Six Input Supply Monitor

FEATURES

DESCRIPTION

The LTC^®2908 is a six input supply monitor for systems

requiring a precise and compact monitoring solution for

multiple supply voltages. The inputs can be shorted to-

gether for monitoring systems with fewer than six supply

voltages, and the open drain RST output of two or more

LTC2908 can be wired-OR together for monitoring sys-

tems with more than six supply voltages. The common

reset output remains low until all six inputs have been in

compliance for 200ms.

n

Ultralow Voltage Reset: V = 0.5V Guaranteed*

CC

n

Monitors Six Inputs Simultaneously:

5V, 3.3V, 2.5V, 1.8V, ADJ1, ADJ2 (LTC2908-A1)

3.3V, 2.5V, 1.8V, 1.5V, ADJ1, ADJ2 (LTC2908-B1)

2.5V, ADJ1, ADJ2, ADJ3, ADJ4, ADJ5

(LTC2908-C1)

n

Guaranteed Threshold Accuracy: 1.5% of

Monitored Voltage Over Temperature

n

Internal V Auto Select

CC

Power Supply Glitch Immunity

The LTC2908 features a tight 1.5% threshold accuracy

over the entire operating temperature range and glitch

immunity to ensure reliable reset operation without false

triggering. Theopen-drainRSToutput state is guaranteed

to be in the correct state as long as V1 and/or V2 is 0.5V

or greater.

200ms Reset Time Delay

Active Low Open-Drain RST Output

Low Proﬁle (1mm) 8-Lead SOT-23 (ThinSOT™) and

Plastic (3mm × 2mm) DFN Packages

APPLICATIONS

TheLTC2908alsofeaturesadjustableinputswithanominal

threshold level at 0.5V. This product provides a precise,

space-conscious, micropower and general purpose solu-

tion for any kind of system requiring supply monitors.

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

is a trademark of Linear Technology Corporation. All other trademarks are the property of

their respective owners. *Patent pending.

n

Network Servers

n

Wireless Base Stations

n

Optical Networking Systems

Multivoltage Systems

Desktop and Notebook Computers

n

TYPICAL APPLICATION

Six Supply Monitor with 5% Tolerance

(12V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V)

12V

RST Output Voltage vs V1

with 10k Pull-Up Resistor to V1

3.3V

2.5V

1.8V

DC/DC

0.4

V3 = V4 = V

=

ADJ1

=

V

ADJ2

V

ADJ4

= V

ADJ3

= V

ADJ5

= GND

0.3

0.2

0.1

0

SYSTEM

V1 INPUT

1.5V

1.2V

V2 = GND

0.1μF 0.1μF

2.15M

V

LTC2908-B1

GND

124k

V

100k

V2 = V1 (A1/B1)

V1

V2 V3 V4

ADJ1

ADJ2

0.4

0

0.2

0.6

0.8

V1 (V)

RST

2908 TA01a

2908 TA01b

2908fc

1

LTC2908

ABSOLUTE MAXIMUM RATINGS ^{(Notes 1, 2)}

Storage Temperature Range

Terminal Voltages

DFN Package......................................–65°C to 125°C

TSOT-23 Package...............................–65°C to 150°C

Lead Temperature (Soldering, 10 sec) .................. 300°C

V1, V2, V3, V4 .........................................–0.3V to 7V

V

, V

,..................–0.3V to (V + 0.6V)

ADJ1 ADJ2 ADJ3 CC

V

, V

.............................–0.3V to (V + 0.6V)

ADJ4 ADJ5 CC

RST.......................................................... –0.3V to 7V

Operating Temperature Range

LTC2908C ................................................ 0°C to 70°C

LTC2908I..............................................–40°C to 85°C

PIN CONFIGURATION

LTC2908CDDB-A1

LTC2908IDDB-A1

LTC2908CDDB-B1

LTC2908IDDB-B1

LTC2908CDDB-C1

LTC2908IDDB-C1

LTC2908CTS8-A1

LTC2908ITS8-A1

LTC2908CTS8-B1

LTC2908ITS8-B1

LTC2908CTS8-C1

LTC2908ITS8-C1

TOP VIEW

GND

RST

V4

1

2

3

4

8

7

6

5

V

GND

1

2

3

4

8

7

6

5

V

ADJ4

V

ADJ3

V

ADJ2

V

ADJ1

ADJ2

TOP VIEW

V2 1

TOP VIEW

V1 1

V3

V

RST

8 V1

7 V

8 V

7 V

ADJ1

ADJ2

9

V

ADJ1

ADJ5

V1

ADJ1

V4 2

RST 3

GND 4

V

2

ADJ5

V2

V1

6 V3

5 V

RST 3

GND 4

6 V

5 V

ADJ3

ADJ4

ADJ2

DDB8 PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

= 125°C, θ = 76°C/W

DDB8 PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

= 125°C, θ = 76°C/W

TS8 PACKAGE

8-LEAD PLASTIC TSOT-23

T

JMAX

T

JMAX

T

= 125°C, θ = 250°C/W

T

= 125°C, θ = 250°C/W

JA

JMAX

JA

JMAX

JA

EXPOSED PAD (PIN 9)

(PCB CONNECTION OPTIONAL)

EXPOSED PAD (PIN 9)

(PCB CONNECTION OPTIONAL)

ORDER INFORMATION

Lead Free Finish

TAPE AND REEL (MINI)

TAPE AND REEL

PART MARKING* PACKAGE DESCRIPTION

TEMPERATURE RANGE

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

LTC2908CDDB-A1#TRMPBF

LTC2908IDDB-A1#TRMPBF

LTC2908CDDB-B1#TRMPBF

LTC2908IDDB-B1#TRMPBF

LTC2908CDDB-C1#TRMPBF

LTC2908IDDB-C1#TRMPBF

LTC2908CTS8-A1#TRMPBF

LTC2908ITS8-A1#TRMPBF

LTC2908CTS8-B1#TRMPBF

LTC2908ITS8-B1#TRMPBF

LTC2908CTS8-C1#TRMPBF

LTC2908ITS8-C1#TRMPBF

LTC2908CDDB-A1#TRMPBF

LTC2908IDDB-A1#TRMPBF

LTC2908CDDB-B1#TRMPBF

LTC2908IDDB-B1#TRMPBF

LTC2908CDDB-C1#TRMPBF

LTC2908IDDB-C1#TRMPBF

LTC2908CTS8-A1#TRMPBF

LTC2908ITS8-A1#TRMPBF

LTC2908CTS8-B1#TRMPBF

LTC2908ITS8-B1#TRMPBF

LTC2908CTS8-C1#TRMPBF

LTC2908ITS8-C1#TRMPBF

LBFD

LBFF

LBFG

LBFH

LCFV

8-LEAD (3mm × 2mm) PLASTIC DFN

8-LEAD PLASTIC TSOT-23

LCFV

LTBFJ

LTBFK

LTBFM

LTBFN

LTCFT

8-LEAD PLASTIC TSOT-23

–40°C to 85°C

TRM = 500 pieces. *Temperature grades are identiﬁed by a label on the shipping container.

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

Consult LTC Marketing for information on lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

2908fc

2

LTC2908

ELECTRICAL CHARACTERISTICS ^{(LTC2908-A1) The}● denotes speciﬁcations which apply over the full

operating temperature range, otherwise speciﬁcations are T_A= 25°C, V_CC= 5V unless otherwise noted. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

4.750

3.135

2.375

1.710

0.508

UNITS

l

V

RT50

V

RT33

V

RT25

V

RT18

V

RTADJ

5V, 5% Reset Threshold

3.3V, 5% Reset Threshold

2.5V, 5% Reset Threshold

1.8V, 5% Reset Threshold

ADJ, 5% Reset Threshold

V1 Input Threshold

V2 Input Threshold

V3 Input Threshold

V4 Input Threshold

4.600

3.036

2.300

1.656

0.492

4.675

3.086

2.338

1.683

0.500

V

, V

Input Threshold

ADJ1 ADJ2

(LTC2908-B1) The ● denotes speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are

T_A= 25°C, V_CC= 3.3V unless otherwise noted. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

3.135

2.375

1.720

1.425

0.508

UNITS

l

V

RT33

V

RT25

V

RT18

V

RT15

V

RTADJ

3.3V, 5% Reset Threshold

2.5V, 5% Reset Threshold

1.8V, 5% Reset Threshold

1.5V, 5% Reset Threshold

ADJ, 5% Reset Threshold

V1 Input Threshold

V2 Input Threshold

V3 Input Threshold

V4 Input Threshold

3.036

2.300

1.656

1.380

0.492

3.086

2.338

1.683

1.403

0.500

V

, V

Input Threshold

ADJ1 ADJ2

(LTC2908-C1) The ● denotes speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are

T_A= 25°C, V_CC= 2.5V unless otherwise noted. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

2.5V, 5% Reset Threshold

ADJ, 5% Reset Threshold

V1 Input Threshold

2.300

2.338

2.375

V

RT25

V

, V

,

RTADJ

ADJ1 ADJ2 ADJ3 ADJ4 ADJ5

Input Threshold

0.492

0.500

0.508

V

The ● denotes speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are T_A= 25°C. V_CC= 5V

for the LT2908-A1, V_CC= 3.3V for the LTC2908-B1or V_CC= 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

Internal Supply Voltage

V1 Input Current (Note 4)

RST in Correct Logic State

0.5

6

V

CC

l

I

V1

V1 = 5.0V (LTC2908-A1)

V1 = 3.3V (LTC2908-B1)

V1 = 2.5V (LTC2908-C1)

26

24

22

70

μA

l

I

V2 Input Current (Note 4)

V3 Input Current

V2 = 3.3V (LTC2908-A1)

V2 = 2.5V (LTC2908-B1)

10

8

30

μA

V2

l

V3 = 2.5V (LTC2908-A1)

V3 = 1.8V (LTC2908-B1)

2

5

μA

V3

l

V4 Input Current

V4 = 1.8V (LTC2908-A1)

V4 = 1.5V (LTC2908-B1)

2

5

μA

V4

l

V

, V

V

= V

= V =

ADJ5

15

nA

VADJ

ADJ1 ADJ2, ADJ3, ADJ4, ADJ5

ADJ1

ADJ2

ADJ3

ADJ4

Input Current

0.55V

2908fc

3

LTC2908

ELECTRICAL CHARACTERISTICS

The ● denotes speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are T_A= 25°C. V_CC= 5V

for the LT2908-A1, V_CC= 3.3V for the LTC2908-B1 or V_CC= 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

200

250

MAX

UNITS

ms

l

t

Reset Time-Out Period

160

260

RST

V Undervoltage Detect to RST

X

V Less Than Reset Threshold V

by

μs

UV

X

RTX

More Than 1%

l

V

Output Voltage High RST (Note 5)

Output Voltage Low RST

I

= –1μA, V = 5V (LTC2908-A1)

V

CC

V

CC

V

CC

– 1.5

– 1.0

V

OH

OL

RST

CC

= –1μA, V = 3.3V (LTC2908-B1)

CC

= –1μA, V = 2.5V (LTC2908-C1)

CC

l

V

= 0.5V, I

= 1.0V, I

= 3.0V, I

= 5μA

= 100μA

= 2500μA

0.01

0.10

0.15

0.30

V

CC

RST

Note 3: All currents into pins are positive; all voltages are referenced to

GND unless otherwise noted.

Note 4: Under typical operating conditions, most of the quiescent cur-

rent is drawn from the V1 input. When V2 exceeds V1, V2 supplies most

of the quiescent current.

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliabilty and lifetime.

Note 2: The greater of V1, V2 is the internal supply voltage (V ) for the

CC

LTC2908-A1 and the LTC2908-B1. V1 is the internal supply voltage (V

for the LTC2908-C1.

)

Note 5: The output pin RST has an internal pull-up to V of typically

6μA. However, an external pull-up resistor may be used when a faster

CC

rise time is required or for V voltages greater than V

.

OH

CC

TYPICAL PERFORMANCE CHARACTERISTICS

Speciﬁcations are at T_A= 25°C unless otherwise noted.

5V Threshold Voltage

vs Temperature

3.3V Threshold Voltage

vs Temperature

2.5V Threshold Voltage

vs Temperature

3.135

3.115

3.095

3.075

3.055

3.035

4.750

4.725

4.700

4.675

4.650

4.625

4.600

2.375

2.360

2.345

2.330

2.315

2.300

50

TEMPERATURE (°C)

100

–50 –25

0

25

75

50

TEMPERATURE (°C)

100

50

TEMPERATURE (°C)

100

–50 –25

0

25

75

–50 –25

0

25

75

2908 G02

2908 G01

2908 G03

2908fc

4

LTC2908

TYPICAL PERFORMANCE CHARACTERISTICS

Speciﬁcations are at T_A= 25°C unless otherwise noted.

1.8V Threshold Voltage

vs Temperature

1.5V Threshold Voltage

vs Temperature

ADJ Threshold Voltage

vs Temperature

1.710

1.700

1.690

1.680

1.670

1.660

1.425

1.420

1.415

1.410

1.405

1.400

1.395

1.390

1.385

1.380

0.5080

0.5060

0.5040

0.5020

0.5000

0.4980

0.4960

0.4940

0.4920

50

TEMPERATURE (°C)

100

–50 –25

0

25

75

–25

0

50

–50

75

100

25

–50

–25

0

25

100

50

75

TEMPERATURE (°C)

2908 G04

2908 G06

2908 G05

I_V1vs Temperature

I_V2vs Temperature

I_V3vs Temperature

33

31

29

27

25

23

21

19

17

14

2.2

2.1

2.0

1.9

V1 = 5.0V (A1)/V1 = 3.3V (B1)/V1 = 2.5V (C1)

V2 = 3.3V (A1)/V2 = 2.5V (B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V1 = 1.5V (B1)

V1 = 5.0V (A1)/V1 = 3.3V (B1)

V2 = 3.3V (A1)/V2 = 2.5V (B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V4 = 1.5V (B1)

13 V2 = 3.3V (A1)/V2 = 2.5V (B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

12

V4 = 1.8V (A1)/V4 = 1.5V (B1)

V

= V

=

V

= V

= 0.55V

V

= V

= 0.55V

ADJ1

ADJ4

ADJ2

ADJ5

ADJ3

ADJ1

ADJ2

ADJ1

ADJ2

11

10

9

=V

= 0.55V

A1

B1

A1

B1

1.8

1.7

8

C1

7

1.6

1.5

1.4

6

5

4

–50

0

25

50

75

100

–25

0

50

–25

0

50

–50

75

100

–50

75

100

25

TEMPERATURE (°C)

2908 G07

2908 G08

2908 G09

Typical Transient Duration

vs Comparator Overdrive

Reset Time-Out Period (t_RST

)

I_V4vs Temperature

vs Temperature

700

600

500

400

300

200

100

0

2.2

2.1

2.0

1.9

250

240

230

220

210

200

190

180

170

160

150

T

= 25°C

A

V1 = 5.0V (A1)/V1 = 3.3V (B1)

V2 = 3.3V (A1)/V2 = 2.5V (B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V4 = 1.5V (B1)

RESET OCCURS

ABOVE CURVE

V

= V

= 0.55V

ADJ1

ADJ2

1.8

1.7

1.6

1.5

1.4

0.1

1

10

100

–25

0

50

–25

0

50

–50

75

100

–50

75

100

25

COMPARATOR OVERDRIVE VOLTAGE (% OF V

)

TEMPERATURE (°C)

RTX

2908 G11

2908 G10

2908 G12

2908fc

5

LTC2908

TYPICAL PERFORMANCE CHARACTERISTICS

Speciﬁcations are at T_A= 25°C unless otherwise noted.

RST Pull-Down Current vs

Supply Voltage

LTC2908-A1/LTC2908-B1

RST Output Voltage vs V1 with

10k Pull-Up Resistor to V1

5.0

4.0

3.0

2.0

1.0

0

0.4

0.3

0.2

0.1

0

6

5

4

3

2

1

0

V3 = V4 = V

=

V1 = V2 (A1/B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V4 = 1.5V (B1)

V

= V1 = V2

ADJ1

CC

V

ADJ1

ADJ4

= GND (A1/B1)

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V4 = 1.5V (B1)

ADJ2

= V

V

= V

=

ADJ2

ADJ3

V

= V

= GND (C1)

ADJ5

V

= V

= 0.55V

=

V

ADJ1

= V

ADJ2

= 0.55V

ADJ1

ADJ4

ADJ2

ADJ5

ADJ3

RST AT

V1 = INPUT

150mV

V

RT33

LTC2908-B1

V2 = GND

RST AT

50mV

V

RT50

V2 = V1

V

RT50

RT25

V

RT33

LTC2908-C1

LTC2908-A1

LTC2908-B1 LTC2908-A1

0.4

V1 (V)

0

0.2

0.6

0.8

0

1

2

3

4

5

0

1

2

3

4

5

V1 (V)

SUPPLY VOLTAGE, V (V)

CC

2908 G14

2908 G13

2908 G15

RST Pull-Down Current vs

Supply Voltage

LTC2908-C1

RST Pull-Down Current vs

Supply Voltage with 2 Inputs

LTC2908-A1/LTC29089-B1

RST Pull-Down Current vs

Supply Voltage with 1 Input

10

1

10

1

4.0

3.5

3.0

2.5

V

= V1 = V2

V

= V1

CC

V

= V1

= V

CC

ADJ1

ADJ4

RST AT 150mV

V3 = V4 = V

= V

= GND

V2 = V3 = V4 = V

= V

=

ADJ2

= V =

ADJ3

= 0.55V

ADJ1

ADJ2

ADJ1

ADJ2

ADJ5

V

= V

= GND

ADJ5

= V

ADJ3

ADJ4

RST AT 150mV

0.1

0.01

0.1

0.01

2.0

1.5

RST AT 50mV

1.0

0.5

0

V

RT25

LTC2908-C1

0.001

0.5

1.0

2.0

0

2.5

1.5

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

SUPPLY VOLTAGE V (V)

SUPPLY VOLTAGE, V (V)

CC

2908 G16

2908 G17

2928 G25

RST Output Voltage Low vs

RST Pull-Down Current

LTC2908-A1

RST Output Voltage Low vs

RST Pull-Down Current

LTC2908-B1

RST Output Voltage Low vs

RST Pull-Down Current

LTC2908-C1

0.8

1.20

1.0

V1 = 5.0V

V2 = 3.3V

V3 = 2.5V

V4 = 1.8V

V1 = 3.3V

V2 = 2.5V

V3 = 1.8V

V4 = 1.5V

V1 = 2.5V

85°C

25°C

V

= V

=

ADJ3

ADJ1

ADJ4

ADJ2

ADJ5

0.7

0.6

0.7

0.6

= 0.4V

V

= V

ADJ2

= 0.4V

V

= V

= 0.4V

ADJ2

ADJ1

0.80

0.60

0.5

0.4

0.3

0.2

0.1

0.5

0.4

0.3

0.2

0.1

85°C

–40°C

25°C

85°C

–40°C

25°C

–40°C

0.40

0.20

0.00

0

5

10

20

25

30

35

5

10

20

(mA)

25

0

15

0

15

0.0

5.0 20.0

RST PULL-DOWN CURRENT, I (mA)

RST

10.0

15.0

25.0

RST PULL-DOWN CURRENT, I

(mA)

RST PULL-DOWN CURRENT, I

RST

2908 G23

2908 G18

2908 G19

2908fc

6

LTC2908

TYPICAL PERFORMANCE CHARACTERISTICS

Speciﬁcations are at T_A= 25°C unless otherwise noted.

RST Output Voltage High vs

RST Output Source Current

LTC2908-A1

RST Pull-Up Current vs

Supply Voltage

–30

5

4

3

2

1

V

= V1 = V2 (A1/B1), V = V1(C1)

CC

V3 = 2.5V (A1)/V3 = 1.8V (B1)

V4 = 1.8V (A1)/V4 = 1.5V (B1)

–25

–20

–15

V

= V

= 0.55V (A1/B1)

ADJ3

ADJ1

ADJ5

ADJ2

= V

=

ADJ4

= 0.55V(C1)

RST HELD AT 0V

V

RT25

LTC2908-C1

25°C

V

–10

–5

0

RT33

LTC2908-B1

–40°C

85°C

V1 = 5.0V

V2 = 3.3V

V3 = 2.5V

V4 = 1.8V

V

RT50

LTC2908-A1

V

= V

= 0.55V

ADJ2

ADJ1

1.5

2

2.5

3

3.5

4

4.5

5

0

–4

–8

–12

–16

(μA)

–20

SUPPLY VOLTAGE, V (V)

OUTPUT SOURCE CURRENT, I

RST

CC

2908 G20

2908 G21

RST Output Voltage High vs

RST Output Source Current

LTC2908-B1

RST Output Voltage High vs

RST Output Source Current

LTC2908-C1

3.0

2.5

2.0

1.5

2.0

1.5

1.0

0.5

85°C

25°C

85°C

V1 = 3.3V

V2 = 2.5V

V3 = 1.8V

V4 = 1.5V

–40°C

1.0

0.5

–40°C

V1 = 2.5V

V

= V

ADJ3

= 0.55V

=

ADJ1

ADJ4

ADJ2

ADJ5

V

= V

= 0.55V

ADJ1

ADJ2

–4

OUTPUT SOURCE CURRENT, I

25°C

0

–6

–8

–10

(μA)

–12

–2

0

–1 –2 –3 –4 –5 –6 –7 –8

OUTPUT SOURCE CURRENT, I (μA)

RST

2908 G22

2908 G24

(TS8 Package/DDB8 Package) LTC2908-A1/LTC2908-B1

PIN FUNCTIONS

V2 (Pin 1/Pin 4): Voltage Input 2. The greater of V1, V2 is

V

(Pin5/Pin8):AdjustableVoltageInput2.SeeTable 1

ADJ2

also the internal V . The operating voltage on this pin shall

for recommended ADJ resistors values.

CC

notexceed6V. Wheninnormaloperation(V1>V2), thispin

draws approximately 8μA. When this pin is acting as the

CC

V3 (Pin 6/Pin 7): Voltage Input 3.

V

ADJ1

(Pin7/Pin6):AdjustableVoltageInput1.SeeTable 1

V

(V2 > V1), this pin draws an additional 16μA. Bypass

for recommended ADJ resistors values.

this pin to ground with a 0.1μF (or greater) capacitor.

V1 (Pin 8/Pin 5): Voltage Input 1. The greater of V1, V2 is

V4 (Pin 2/Pin 3): Voltage Input 4.

also the internal V . The operating voltage on this pin shall

CC

RST (Pin 3/Pin 2): Reset Logic Output. Pulls low when

any voltage input is below the reset threshold and is held

low for 200ms after all voltage inputs are above threshold.

not exceed 6V. When in normal operation (V1 > V2), this pin

draws approximately 26 μA. When this pin is not acting as

theV (V2>V1),thispindrawsapproximately8μA.Bypass

CC

Thispinhasaweakpull-uptoV andmaybepulledabove

CC

this pin to ground with a 0.1μF (or greater) capacitor.

V

CC

using an external pull-up.

Exposed Pad (Pin 9, DDB8 Only): Exposed Pad may be

GND (Pin 4/Pin 1): Device Ground.

left open or connected to device ground.

2908fc

7

LTC2908

(TS8 Package/DDB8 Package) LTC2908-C1

PIN FUNCTIONS

GND (Pin 4/Pin 1): Device Ground.

(Pin 5/Pin 8): Adjustable Voltage Input 4.

V1 (Pin 1/Pin 4): Voltage Input 1. V1 is the internal V .

CC

The operating voltage on this pin shall not exceed 6V.

When in normal operation, this pin draws approximately

22μA. Bypass this pin to ground with a 0.1μF (or greater)

capacitor.

V

ADJ4

See Table 1 for recommended ADJ resistors values.

V

(Pin 6/Pin 7): Adjustable Voltage Input 3.

ADJ3

See Table 1 for recommended ADJ resistors values.

V

(Pin 2/Pin 3): Adjustable Voltage Input 5. See Table 1

ADJ5

V

(Pin 7/Pin 6): Adjustable Voltage Input 2.

for recommended ADJ resistors values.

ADJ2

See Table 1 for recommended ADJ resistors values.

RST (Pin 3/Pin 4): Reset Logic Output. Pulls low when

any voltage input is below the reset threshold and is held

low for 200ms after all voltage inputs are above threshold.

Thispinhasaweakpull-uptoVccandmaybepulledabove

Vcc using an external pull-up.

V

(Pin 8/Pin 5): Adjustable Voltage Input 1.

ADJ1

See Table 1 for recommended ADJ resistors values.

Exposed Pad (Pin 9, DDB8 Only): Exposed Pad may be

left open or connected to device ground.

BLOCK DIAGRAMS

LTC2908-A1/LTC2908-B1

V1

V2

V3

–

+

C1

C2

C3

C4

C5

POWER

DETECT

V

CC

–

+

V

CC

–

+

6μA

RST

200ms

RESET PULSE

GENERATOR

–

+

V4

V

–

+

ADJ1

V

–

+

ADJ2

C6

GND

BANDGAP

REFERENCE

2908 BD

2908fc

8

LTC2908

BLOCK DIAGRAMS

LTC2908-C1

V1

–

+

C1

C2

C3

C4

C5

V

–

+

ADJ1

V1

V

–

+

ADJ2

6μA

RST

200ms

RESET PULSE

GENERATOR

V

–

+

ADJ3

V

–

+

ADJ4

V

–

+

ADJ5

C6

GND

BANDGAP

REFERENCE

2908 BDa

TIMING DIAGRAM

V_XMonitor Timing

V

RTX

V

X

t

RST

UV

1V

RST

2908 TD

2908fc

9

LTC2908

APPLICATIONS INFORMATION

Such an indeterminate voltage may trigger external logic

causing erroneous reset operation(s). Furthermore, a

mid-scale voltage level could cause external circuits to

operate in the middle of their voltage transfer character-

istic, consuming more quiescent current than normal.

These conditions could cause serious system reliability

problems.

Supply Monitoring

The LTC2908 is a low power, high accuracy, six input

supply monitoring circuit with two adjustable inputs. The

reset delay is set to a nominal of 200ms with an internal

capacitor, eliminating the need for an external timing

capacitor.

Allinputvoltagesmustbeabovepredeterminedthresholds

for the reset not to be invoked. The LTC2908 asserts the

reset output during power-up, power-down and brownout

conditions on any one of the voltage inputs.

Power-Up

During power-up, RST starts asserting low as soon as

there is at least 200mV on V1 and/or V2. The RST pull-

down capability is a function of V1 and V2 as shown in

the Typical Performance Characteristics.

Ultralow Voltage Pull-Down on RST

The LTC2908 issues a logic low on the RST output when

any one of the inputs falls below its threshold. Ideally, the

RST logic output would remain low with the input supply

voltage down to zero volts. Most supervisors lack pull-

down capability below 1V.

The greater of V1, V2 is the internal supply voltage (V )

CC

that powers the other internal circuitry. Once all the V

X

inputs rise above their thresholds, an internal timer is

started. After the internal timer counts a 200ms delay

time, RST weakly pulls high to V .

CC

The LTC2908 power supply supervisor incorporates a

novel low voltage pull-down circuit that can hold the RST

line low with as little as 200mV of input supply voltage on

V1 and/or V2 (see Figures 1 and 2). The pull-down circuit

helps maintain a low impedance path to ground, reducing

the risk of the RST node from ﬂoating to an indeterminate

voltage.

Power-Down

On power-down, once any of the V inputs drop below

X

their threshold, RST asserts logic low. V of at least 0.5V

CC

guarantees a logic low of 0.15V at RST.

10

V

= V1 = V2

V

= V1

CC

V3 = V4 = V

= V

ADJ2

= GND

V2 = V3 = V4 = V

= V

ADJ5

=

ADJ1

ADJ2

V

= V

= GND

ADJ3

ADJ4

1

0.1

1

0.1

RST AT 150mV

RST AT 50mV

0.01

0.001

0.01

0.001

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

SUPPLY VOLTAGE, V (V)

CC

2908 G16

2908 G17

Figure 1.RST Pull-Down Current vs

Supply Voltage with 2 Inputs LTC2908-A1/

LTC2908-B1

Figure 2.RST Pull-Down Current vs

Supply Voltage with 1 Input

2908fc

10

LTC2908

APPLICATIONS INFORMATION

Adjustable Input

In an application with less than six supply voltages, the

unused supervisor inputs should be tied to the closest

higher supply voltage available.

The noninverting input on the V

comparator is set to

ADJ

0.5V. And the high impedance inverting input directly ties

to the V pin.

ADJ

Threshold Accuracy

In a typical application, this pin connects to a tap point

on an external resistive divider between the positive

voltage being monitored and ground (see Figure 3). The

following formula derives the value of the R1 resistor in

the divider from a particular value of R2 and the desired

trip voltage:

Specifyingsystemvoltagemarginforworst-caseoperation

requires the consideration of three factors: power supply

tolerance,ICsupplyvoltagetoleranceandsupervisorreset

threshold accuracy. Highly accurate supervisors ease the

design challenge by decreasing the overall voltage margin

required for reliable system operation. Consider a 5V

system with a 5% power supply tolerance band.

ꢀ

ꢃ

V_TRIP

0.5V

R1=

–1 R2

ꢅ

ꢂ

ꢁ

ꢄ

System ICs powered by this supply must operate reliably

within this band (and a little more, as explained below).

The bottom of the supply tolerance band, at 4.75V (5%

below 5V), is the exact voltage at which a perfectly ac-

curate supervisor generates a reset (see Figure 4). Such

a perfectly accurate supervisor does not exist—the

actual reset threshold may vary over a speciﬁed band

( 1.5% for the LTC2908 supervisors). Figure 5 shows

the typical relative threshold accuracy for all six inputs

over temperature.

R2 = 100k is recommended. Table 1 shows suggested

1% resistor values for various adjustable applications and

their corresponding trip thresholds.

Table 1. Suggested 1% Resistor Values for the V_ADJInputs

V

(V)

V

(V)

R1 (kΩ)

2150

1780

1400

1300

1020

845

511

464

365

237

R2 (kΩ)

100

SUPPLY

TRIP

12

11.25

9.4

10

8

7.5

6

5

3.3

3

2.5

1.8

1.5

1.2

1.0

0.9

0.8

0.7

0.6

7.5

7

5.6

NOMINAL

SUPPLY

VOLTAGE

5.000V

4.725

3.055

2.82

MINIMUM

SUPPLY

IDEAL

RELIABLE TOLERANCE SUPERVISOR

SYSTEM

VOLTAGE

THRESHOLD

4.750V

4.675V

4.600V

–5.0%

–6.5%

1.5%

THRESHOLD

BAND

2.325

1.685

1.410

1.120

0.933

0.840

0.750

0.655

0.561

2.5%

THRESHOLD

BAND

–8.0%

REGION OF POTENTIAL MALFUNCTION

WITH 2.5% MONITOR

182

124

4.500V

–10%

2908 F04

86.6

68.1

49.9

30.9

12.1

Figure 4. Threshold Band Diagram

1.5

1.0

V

0.5

TRIP

LTC2908-A1/LTC2908-B1/LTC2908-C1

R1

1%

0

V

ADJ

–

R2

1%

–0.5

–1.0

–1.5

+

0.5V

–

–50

0

25

50

75

100

–25

TEMPERATURE (°C)

2908 F05

2908 F03

Figure 3. Setting the Adjustable Trip Point

Figure 5. Typical Threshold Accuracy vs Temperature

2908fc

11

LTC2908

APPLICATIONS INFORMATION

With this variation of reset threshold in mind, the nomi-

nal reset threshold of the supervisor resides below the

minimum supply voltage; just enough so that the reset

threshold band and the power supply tolerance bands

do not overlap. If the two bands overlap, the supervisor

could generate a false or nuisance reset when the power

supply remains within its speciﬁed tolerance band (for

example at 4.8V).

Therefore,theLTC2908takesadifferentapproachtosolv-

ing this problem of supply noise causing spurious reset.

The ﬁrst line of defense against this spurious reset is a

ﬁrst order lowpass ﬁlter at the output of the comparators.

Therefore, each comparator output is integrated over time

before triggering the output logic. Therefore, any kind of

transient at the input of the comparator needs to be of

sufﬁcient magnitude and duration before it can trigger a

change in the output logic.

Adding half of the reset threshold accuracy spread (1.5%)

to the ideal 5% thresholds puts the LTC2908 thresholds at

6.5% (typ) below the nominal input voltage. For example,

the 5V typical threshold is 4.675V, or 75mV below the

ideal threshold of 4.750V. The guaranteed threshold lies

in the band between 4.600V (8% below 5V) and 4.750V

(5% below 5V) over temperature.

The second line of defense is the 200ms delay time t

.

RST

Thisdelayeliminatestheeffectofanysupplynoise,whose

frequency is above 1/200ms = 5Hz, on the RST output.

When any one of the supply voltages drops below its

threshold, the RST pin asserts low. When the supply

recovers above its threshold, the reset-pulse-generator

timer starts counting.

Thepoweredsystemmustworkreliablydowntothelowest

voltage in the threshold band or risk malfunction before

the reset line falls. In the 5V example, using the 1.5%

accurate supervisor, the system ICs must work down to

4.60V (8% below 5V). System ICs working with a 2.5%

accurate supervisor must operate down to 4.50V (10%

below 5V), increasing the required system voltage margin

and the probability of system malfunction.

Ifallthesuppliesremainabovetheircorrespondingthresh-

old when the timer ﬁnishes counting, the RST pin weakly

pulls high. However, if any of the supplies falls below its

threshold any time during the period when the timer is still

counting, the timer resets and it starts fresh when all the

supplies rise above their corresponding threshold.

Note that this second line of defense is only effective

for a rising supply and does not affect the sensitivity of

the system to a falling supply. Therefore, the ﬁrst line of

defense that works for both cases of rising and falling is

necessary. These two approaches prevent spurious reset

caused by supply noise without sacriﬁcing the threshold

accuracy.

In any supervisory application, supply noise riding on

the monitored DC voltage can cause spurious resets,

particularly when the monitored voltage is near the reset

threshold. A less desirable but common solution to this

problem is to introduce hysteresis around the nominal

threshold. Notice however, this hysteresis introduces an

error term in the threshold accuracy. Therefore, a 2.5%

accurate monitor with 1% hysteresis is equivalent to a

3.5% monitor with no hysteresis.

Although all six comparators for the six inputs have built-

in glitch ﬁltering, use bypass capacitors on the V1 and

V2 inputs because the greater of V1 or V2 supplies the

V

for the part (a 0.1μF ceramic capacitor satisﬁes most

CC

applications). Apply ﬁlter capacitors on the V3, V4, V

,

ADJ1

V

, V

and V

inputs in extremely noisy

ADJ2 ADJ3 ADJ4

ADJ5

situations.

2908fc

12

LTC2908

APPLICATIONS INFORMATION

RST Output Characteristics

transistor estimated to be typically 40Ω at room tempera-

ture (25°C) and C

is the external load capacitance on

LOAD

The DC characteristics of the RST pull-up and pull-down

strength are shown in the Typical Performance Character-

istics section. The RST output has a weak internal pull-up

the pin. Assuming a 150pF load capacitance, the fall time

is about 13ns.

to V = Max(V1, V2) and a strong pull-down to ground.

The rise time on the RST pin is limited by a weak internal

CC

pull-up current source to V . The following formula esti-

CC

The weak pull-up and strong pull-down arrangement al-

lowsthispintohaveopen-drainbehaviorwhilepossessing

several other beneﬁcial characteristics.

mates the output rise time (10% to 90%) at the RST pin:

t

≈ 2.2 • R • C

PU LOAD

RISE

The weak pull-up eliminates the need for external pull-up where R is the on-resistance of the pull-up transis-

PU

resistors when the rise time on these pins is not critical. tor. Notice that this pull-up transistor is modeled as a

On the other hand, the open-drain RST behavior allows for 6μA current source in the Block Diagram as a typical

wired-OR connections and can be useful when more than representation.

one signal needs to pull down on the RST line.

The on-resistance as a function of the V = Max(V1, V2)

CC

As noted in the discussion of power-up and power-down, voltage (for V > 1V) at room temperature is estimated

CC

thecircuitsthatdriveRSTarepoweredbyV_CC.Duringfault as follows:

6 •10⁵

condition, V_CCof at least 0.5V guarantees a maximum

R_PU=

Ω

V_OL= 0.15V at RST

.

MAX V1,V2 –1V

(

)

At V = 3.3V, R is about 260k. Using 150pF for load

Output Rise and Fall Time Estimation

CC

PU

capacitance, the rise time is 86μs. A smaller external

pull-up resistor may be used if the output needs to pull

up faster and/or to a higher voltage. For example, the rise

time reduces to 3.3μs for a 150pF load capacitance when

using a 10k pull-up resistor.

Thefollowingformulaestimatestheoutputfalltime(90%to

10%) for a particular external load capacitance (C

):

LOAD

t

≈ 2.2 • R • C

PD LOAD

FALL

where R is the on-resistance of the internal pull-down

PD

TYPICAL APPLICATIONS

Six Supply Monitor, 5% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1V

12V

5V

DC/DC

3.3V

2.5V

SYSTEM

1.8V

1.0V

C1

C2

0.1μF 0.1μF

R1

2.15M

R3

86.6k

R2

100k

R4

100k

V1

V2 V3 V4

V

ADJ2

ADJ1

LTC2908-A1

GND

RST

2908 TA02

2908fc

13

LTC2908

TYPICAL APPLICATIONS

Quad Supply Monitor with One Adjustable Input, 5% Tolerance, 3.3V, 2.5V, 1.8V, 1.2V

3.3V

2.5V

1.8V

1.2V

DC/DC

SYSTEM

C1

C2

0.1μF 0.1μF

R3

124k

R4

100k

V1

V2

V3 V4

LTC2908-B1

GND

V

ADJ1

ADJ2

RST

2908 TA03

Pin Programmable Dual Supply Monitor with Possible Future Expansion up to Six Supplies, 5% Tolerance, 3.3V and 2.5V

3.3V

SYSTEM

2.5V

DC/DC

C1

0.1μF

C2

0.1μF

V1

V2 V3 V4

LTC2908-B1

GND

V

ADJ1 ADJ2

RST

2908 TA05

Six Supply Monitor, 5% Tolerance 12V, 2.5V, 1.8V, 1.5V, 1.2V, 1.0V

12V

2.5V

DC/DC

1.8V

1.5V

DC/DC

SYSTEM

1.2V

1.0V

C1

0.1μF

R1

2.15M

R3

237k

R5

182k

R7

124k

R9

86.6k

R2

100k

R4

100k

R6

100k

R8

100k

R10

100k

V1

V

ADJ1

V

ADJ3

V

ADJ5

ADJ2

ADJ4

LTC2908-C1

GND

RST

2908 TA06

2908fc

14

LTC2908

PACKAGE DESCRIPTION

DDB Package

8-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1702 Rev B)

0.61 ±0.05

(2 SIDES)

R = 0.115

0.40 ± 0.10

3.00 ±0.10

(2 SIDES)

TYP

5

R = 0.05

TYP

8

0.70 ±0.05

2.55 ±0.05

1.15 ±0.05

2.00 ±0.10

PIN 1 BAR

TOP MARK

PIN 1

(2 SIDES)

R = 0.20 OR

0.25 × 45°

CHAMFER

(SEE NOTE 6)

PACKAGE

OUTLINE

0.56 ± 0.05

(2 SIDES)

4

1

(DDB8) DFN 0905 REV

B

0.25 ± 0.05

0.75 ±0.05

0.200 REF

0.50 BSC

2.20 ±0.05

(2 SIDES)

0.50 BSC

2.15 ±0.05

(2 SIDES)

0 – 0.05

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE

TS8 Package

8-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1637)

2.90 BSC

(NOTE 4)

0.52

MAX

0.65

REF

1.22 REF

1.50 – 1.75

(NOTE 4)

2.80 BSC

1.4 MIN

3.85 MAX 2.62 REF

PIN ONE ID

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.22 – 0.36

8 PLCS (NOTE 3)

0.65 BSC

0.80 – 0.90

0.20 BSC

DATUM ‘A’

0.01 – 0.10

1.00 MAX

0.30 – 0.50 REF

1.95 BSC

0.09 – 0.20

(NOTE 3)

TS8 TSOT-23 0802

NOTE:

1. DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

5. MOLD FLASH SHALL NOT EXCEED 0.254mm

6. JEDEC PACKAGE REFERENCE IS MO-193

2. DRAWING NOT TO SCALE

3. DIMENSIONS ARE INCLUSIVE OF PLATING

2908fc

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresenta-

t ion t h a t t he in ter c onne c t ion o f i t s cir cui t s a s de s cr ib e d her ein w ill no t in fr inge on ex is t ing p a ten t r igh t s.

15

LTC2908

TYPICAL APPLICATION

Six Supply Monitor with Manual Reset Button, 5% Tolerance, 12V, 5V, 3.3V, 2.5V, 1.8V, 1.5V

12V (V

TRIP

= 11.25V)

5V (V

TRIP

= 4.675V)

DC/DC

3.3V (V

2.5V (V

= 3.086V)

= 2.338V)

TRIP

DC/DC

SYSTEM

TRIP

1.8V (V

1.5V (V

= 1.685V)

= 1.410V)

TRIP

C1

C2

R1

182k

R3

R2

100k

MANUAL

0.1μF 0.1μF

2.15M

RESET BUTTON

(NORMALLY OPEN)

R5*

10k

R4

100k

V1

V2 V3 V4

V

ADJ1

ADJ2

RST

LTC2908-A1

GND

*OPTIONAL RESISTOR RECOMMENDED

TO EXTEND ESD TOLERANCE

2908 TA04

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Precision Triple Supply Monitor for PCI Applications Meets PCI t Timing Speciﬁcations

FAIL

LTC1726-2.5/LTC1726-5 Micropower Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ

LTC1727-2.5/LTC1727-5 Micropower Triple Supply Monitor with Open-Drain Reset

LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset

LTC1728-2.5/LTC1728-5 Micropower Triple Supply Monitor with Open-Drain Reset

Adjustable Reset and Watchdog Time-Outs

Individual Monitor Outputs in MSOP

5-Lead SOT-23 Package

LTC1985-1.8

LTC2900

Micropower Triple Supply Monitor with Push-Pull Reset Output

Programmable Quad Supply Monitor

5-Lead SOT-23 Package

Adjustable Reset, 10-Lead MSOP and DFN Packages

LTC2901

Programmable Quad Supply Monitor

Adjustable Reset and Watchdog Timer,

16-Lead SSOP Package

LTC2902

Programmable Quad Supply Monitor

Adjustable Reset and Tolerance,

16-Lead SSOP Package

LTC2903

LTC2904

LTC2905

Precision Quad Supply Monitor

6-Lead SOT-23 Package

Three-State Programmable Precision Dual Supply Monitor

Adjustable Tolerance, 8-Lead SOT-23 and DFN Packages

Adjustable Reset and Tolerance, 8-Lead SOT-23 and

DFN Packages

LTC2906

LTC2907

LTC2909

Dual Supply Monitor with One Pin Selectable Threshold and

One Adjustable Input

0.5V Adjustable Threshold and Three Supply

Tolerances, 8-Lead SOT-23 and DFN Packages

Dual Supply Monitor with One Pin Selectable Threshold and

One Adjustable Input

0.5V Adjustable Threshold, Reset and Three Supply

Tolerances, 8-Lead SOT-23 and DFN Packages

Precision Triple/Dual Input UV, OV and Negative Voltage Monitor

Shunt Regulated V Pin, Adjustable Threshold and

CC

Reset, 8-Lead SOT-23 and DFN Packages

2908fc

LT 0708 REV C • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LTC2908IDDB-A1#TRMPBF
厂家：	Linear
描述：	暂无描述监视器
文件：	总16页 (文件大小：195K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC2908IDDB-A1#TRMPBF [Linear]

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