Datasheet LTC2902-2IGN, LTC2902-2CGN, LTC2902-1IGN, LTC2902-1CGN Datasheet (Linear Technology)

Monitor with Adjustable Reset Timer

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%, 12.5% 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 VCC ≥ 1V

U

APPLICATIO S

■

Desktop and Notebook Computers

■

Multivoltage Systems

■

Telecom Equipment

■

Portable Battery-Powered Equipment

■

Network Servers

LTC2902

Programmable Quad Supply

and Supply Tolerance

U

DESCRIPTIO

The LTC®2902 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 digitally pro­grammable to 5%, 7.5%, 10% or 12.5% below the nomi­nal operating voltage, and are accurate to 1.5% over tem­perature. All four voltage comparator outputs are con­nected 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 VCC 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.

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

TYPICAL APPLICATIO

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

CONVERTER

DC/DC

U

0.1µF

5V

3.3V

2.5V

1.8V

C1

C2

0.1µF

59k
1%

40.2k
1%

SYSTEM

LOGIC

133

LTC2902-2

GND

10

V4V3

CRT

COMP1
COMP2
COMP3
COMP4

5

4

V1

14

V2

12

V

REF

R1

11

V

R2

PG

RST

RDIS

C
47nF

T0
T1

RT

R3
10k

2
16
1
15
6

8

7

TOLERANCE = 5%

9

2902 TA01

POWER

GOOD

MARGIN

t

RST

= 216ms

2902f

1

LTC2902

PACKAGE/ORDER I FOR ATIO

UU

W

GN PACKAGE

16-LEAD PLASTIC SSOP

1
2
3
4
5
6
7
8

TOP VIEW

16
15
14
13
12
11
10

9

COMP3
COMP1

V3

V1
CRT
RST

T0

RDIS

COMP2
COMP4
V2
V4
V

REF

V

PG

GND
T1

WWWU

ABSOLUTE AXI U RATI GS

(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 + 0.3V)

V

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

REF

Reference Load Current (I

V4 Input Current (–ADJ Mode) ............................ –1mA

Operating Temperature Range

LTC2902-1C/LTC2902-2C ....................... 0°C to 70°C

LTC2902-1I/LTC2902-2I .................... –40°C to 85°C

Storage Temperature Range .................. – 65°C to 150°C

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

) ............................ ±1mA

VREF

ORDER PART

NUMBER

LTC2902-1CGN
LTC2902-2CGN
LTC2902-1IGN
LTC2902-2IGN

GN16 PART MARKING

29021
29022

T

= 125°C, θJA = 130°C/W

JMAX

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

29021I
29022I

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

RT50

V

RT33

V

RT30

V

RT25

V

RT18

V

RT15

V

RTA

2

5V, 5% Reset Threshold V1 Input Threshold ● 4.600 4.675 4.750 V
5V, 7.5% Reset Threshold
5V, 10% Reset Threshold
5V, 12.5% Reset Threshold

3.3V, 5% Reset Threshold V1, V2 Input Threshold ● 3.036 3.086 3.135 V

3.3V, 7.5% Reset Threshold

3.3V, 10% Reset Threshold

3.3V, 12.5% Reset Threshold
3V, 5% Reset Threshold V2 Input Threshold ● 2.760 2.805 2.850 V

3V, 7.5% Reset Threshold
3V, 10% Reset Threshold
3V, 12.5% Reset Threshold

2.5V, 5% Reset Threshold V2, V3 Input Threshold ● 2.300 2.338 2.375 V

2.5V, 7.5% Reset Threshold

2.5V, 10% Reset Threshold

2.5V, 12.5% Reset Threshold

1.8V, 5% Reset Threshold V3, V4 Input Threshold ● 1.656 1.683 1.710 V

1.8V, 7.5% Reset Threshold

1.8V, 10% Reset Threshold

1.8V, 12.5% Reset Threshold

1.5V, 5% Reset Threshold V3, V4 Input Threshold ● 1.380 1.403 1.425 V

1.5V, 7.5% Reset Threshold

1.5V, 10% Reset Threshold

1.5V, 12.5% Reset Threshold
ADJ, 5% Reset Threshold V3, V4 Input Threshold ● 0.492 0.500 0.508 V

ADJ, 7.5% Reset Threshold
ADJ, 10% Reset Threshold
ADJ, 12.5% Reset Threshold

The ● denotes the specifications which apply over the full operating

● 4.475 4.550 4.625 V

● 4.350 4.425 4.500 V

● 4.225 4.300 4.375 V

● 2.954 3.003 3.053 V

● 2.871 2.921 2.970 V

● 2.789 2.838 2.888 V

● 2.685 2.730 2.775 V

● 2.610 2.655 2.700 V

● 2.535 2.580 2.625 V

● 2.238 2.275 2.313 V

● 2.175 2.213 2.250 V

● 2.113 2.150 2.188 V

● 1.611 1.638 1.665 V

● 1.566 1.593 1.620 V

● 1.521 1.548 1.575 V

● 1.343 1.365 1.388 V

● 1.305 1.328 1.350 V

● 1.268 1.290 1.313 V

● 0.479 0.487 0.494 V

● 0.466 0.473 0.481 V

● 0.453 0.460 0.467 V

2902f

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. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

RTAN

V

CC

V

CCMINP

V

CCMINC

V

REF

V

PG

I

VPG

I

V1

I

V2

I

V3

I

V4

I

CRT(UP)

I

CRT(DN)

t

RST

t

UV

V

OL

V

OH

V

OH

Digital Inputs T0, T1, RDIS

V

IL

V

IH

I

INTOL

V

IL

V

IH

I

RDIS

Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.

Note 2: All voltage values are with respect to GND.
Note 3: The greater of V1, V2 is the internal supply voltage (V
Note 4: Under static no-fault conditions, V1 will necessarily supply quiescent

current. If at any time V2 is larger than V1, V2 must be capable of supplying
the quiescent current, programming (transient) current and reference load
current.

–ADJ Reset Threshold V4 Input Threshold ● –18 0 18 mV
Minimum Internal Operating Voltage RST, COMPX in Correct Logic State; ● 1V

VCC Rising Prior to Program
Minimum Required for Programming VCC Rising ● 2.42 V
Minimum Required for Comparators VCC Falling ● 2.32 V
Reference Voltage VCC ≥ 2.3V, I

= ±1mA, C

VREF

≤ 1000pF

REF

T0 Low, T1 Low ● 1.192 1.210 1.228 V

T0 Low, T1 High

● 1.160 1.178 1.195 V

T0 High, T1 Low ● 1.128 1.146 1.163 V

T0 High, T1 High
Programming Voltage Range VCC ≥ V
VPG Input Current VPG = V

CCMINP

REF

V1 Input Current V1 = 5V, I

= 12µA, (Note 4) ● 43 75 µA

VREF

● 1.096 1.113 1.130 V

● 0V

● ±20 nA

REF

V2 Input Current V2 = 3.3V ● 0.8 2 µA
V3 Input Current V3 = 2.5V ● 0.52 1.2 µA

V3 = 0.55V (ADJ Mode) –15 15 nA
V4 Input Current V4 = 1.8V ● 0.34 0.8 µA

V4 = 0.55V (ADJ Mode)

● –15 15 nA

V4 = –0.05V (–ADJ Mode) ● –15 15 nA
CRT Pull-Up Current V
CRT Pull-Down Current V

= 0V ● –1.4 –2 –2.6 µA

CRT

= 1.3V ● 10 20 30 µA

CRT

Reset Time-Out Period CRT = 1500pF ● 579 ms
VX Undervoltage Detect to RST or COMPX VX Less Than Reset Threshold V

RTX

150 µs

by More Than 1%
Output Voltage Low RST, COMPX I

= 2.5mA; V1 = 3V, V2 = 3V; ● 0.15 0.4 V

SINK

V3, V4 = 0V; VPG = 0V

I

= 100µA; V2 = 1V; V1, V3, V4 = 0V ● 0.05 0.3 V

SINK

I

= 100µA; V1 = 1V; V2, V3, V4 = 0V ● 0.05 0.3 V

SINK

Output Voltage High RST, COMPX (Note 5) I
Output Voltage High RST (LTC2902-2) I

= 1µA ● V2 – 1 V

SOURCE

= 200µA ● 0.8 • V2 V

SOURCE

(Note 6)

T0, T1 Low Level Input Voltage VCC = 3.3V to 5.5V ● 0.3V
T0, T1 High Level Input Voltage VCC = 3.3V to 5.5V ● 0.7V
T0, T1 Input Current T0 = 0V, T1 = V

CC

● ±0.1 ±1 µA

CC

CC

RDIS Input Threshold Low VCC = 3.3V to 5.5V ● 0.4 V
RDIS Input Threshold High VCC = 3.3V to 5.5V ● 1.6 V
RDIS Pull-Up Current V

= 0V –10 µA

RDIS

Note 5: The output pins RST and COMPX have internal pull-ups to V2 of
typically 6µA. However, external pull-up resistors may be used when faster

CC

rise times are required or for V

).

Note 6: The push-pull RST output pin on the LTC2902-2 is
to V2.

voltages greater than V2.

OH

actively

pulled up

2902f

V

V
V

3

LTC2902

TEST CIRCUITS

V1
V2
V3
V4

LTC2902-1

2902 F01

RST
OR COMPX

I

SOURCE

1µA

V1
V2
V3
V4

LTC2902-1

2902 F02

RST
OR COMPX

I

SINK

2.5mA,
100µA

V1
V2
V3
V4

LTC2902-2

2902 F03

RST

I

SOURCE

200µA

Figure 1. RST, COMPX VOH Test Figure 2. RST, COMPX VOL Test Figure 3. Active Pull-Up RST VOH Test

UWW

TI I G DIAGRA

VX Monitor Timing

V

RTX

t

t

UV

RST

1.5V

2902 TD

RST

COMPX

V

X

UW

TYPICAL PERFOR A CE CHARACTERISTICS

5V Threshold Voltage
vs Temperature

4.75

4.70

(V)

4.65

RT50

4.60

4.55

4.50

4.45

4.40

4.35

THRESHOLD VOLTAGE, V

4.30

4.25
–60

–20

–40 0

TEMPERATURE (°C)

5%

7.5%

10%

12.5%

20

40

80

60

100

2902 G01

3.3V Threshold Voltage
vs Temperature

3.135

3.100

3.065

(V)

RT33

3.030

2.995

2.960

2.925

2.890

2.855

THRESHOLD VOLTAGE, V

2.820

2.785
–60

–20

–40 0

TEMPERATURE (°C)

5%

7.5%

10%

12.5%

20

60

40

4

80

2902 G02

100

3V Threshold Voltage
vs Temperature

2.850

2.815

(V)

2.780

RT30

2.745

2.710

2.675

2.640

2.605

THRESHOLD VOLTAGE, V

2.570

2.535
–60

–20

–40 0

TEMPERATURE (°C)

5%

7.5%

10%

12.5%

20

40

80

60

100

2902 G03

2902f

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2902

2.5V Threshold Voltage
vs Temperature

2.375

2.350

2.325

(V)

2.300

RT25

2.275

2.250

2.225

2.200

2.175

2.150

THRESHOLD VOLTAGE, V

2.125

2.100
–60

–20

–40 0

TEMPERATURE (°C)

ADJ Threshold Voltage
vs Temperature

0.508

0.503

0.498

(V)

0.493

RTA

0.488

0.483

0.478

0.473

0.468

0.463

THRESHOLD VOLTAGE, V

0.458

0.453
–60

–20

–40 0

TEMPERATURE (°C)

5%

7.5%

10%

12.5%

5%

7.5%

10%

12.5%

1.8V Threshold Voltage
vs Temperature

1.710

1.685

(V)

1.660

RT18

1.635

1.610

1.585

1.560

THRESHOLD VOLTAGE, V

1.535

100

1.510
–60

–40 0

20

40

80

60

2902 G04

5%

7.5%

10%

12.5%

–20

20

TEMPERATURE (°C)

40

100

2902 G05

80

60

1.5V Threshold Voltage
vs Temperature

1.425

1.405

(V)

1.385

RT15

1.365

1.345

1.325

1.305

THRESHOLD VOLTAGE, V

1.285

1.265
–60

–20

–40 0

TEMPERATURE (°C)

5%

7.5%

10%

12.5%

20

40

80

60

100

2902 G06

–ADJ Threshold Voltage
vs Temperature

0.018

0.012

(V)

RTAN

0.006

0

–0.006

–0.012

THRESHOLD VOLTAGE, V

100

–0.018

–60

–40 0

–20

20

TEMPERATURE (°C)

40

100

2902 G08

80

60

20

40

80

60

2902 G07

1.228

1.216

1.204

1.192

1.180

1.168

(V)

REF

1.156

V

1.144

1.132

1.112

1.108

1.096

V

vs Temperature

REF

–60

–20

–40 0

5%

7.5%

10%

12.5%

20

TEMPERATURE (°C)

40

80

60

100

2902 G09

IV1 vs Temperature

100

V1 = 5V

90

V2 = 3.3V
V3 = 2.5V

80

V4 = 1.8V

70
60
50

(µA)

V1

I

40
30
20
10

0

–60

–40 0

–20

20

TEMPERATURE (°C)

40

IV2 vs Temperature

1.5
V1 = 5V

1.4

V2 = 3.3V
V3 = 2.5V

1.3
V4 = 1.8V

1.2

1.1

1.0

(µA)

V2

I

0.9

0.8

0.7

0.6

80

60

100

2902 G10

0.5

–60

–40 0

–20

TEMPERATURE (°C)

80

20

60

40

100

2902 G11

IV3 vs Temperature

1.1
V1 = 5V

1.0

V2 = 3.3V
V3 = 2.5V

0.9
V4 = 1.8V

0.8

0.7

0.6

(µA)

V3

I

0.5

0.4

0.3

0.2

0.1

–60

–40 0

–20

20

TEMPERATURE (°C)

40

80

60

100

2902 G12

2902f

5

LTC2902

UW

TYPICAL PERFOR A CE CHARACTERISTICS

IV4 vs Temperature

1.0
V1 = 5V

0.9

V2 = 3.3V
V3 = 2.5V

0.8
V4 = 1.8V

0.7

0.6

0.5

(µA)

V4

I

0.4

0.3

0.2

0.1

0

–60

–40 0

–20

20

TEMPERATURE (°C)

40

RST Output Voltage
vs V1, VPG = 0V

5

V1 = V2 = V3 = V4
10k PULL-UP FROM RST TO V1
T

= 25°C

4

A

3

2

RST OUTPUT VOLTAGE (V)

1

0

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

V1 (V)

Typical Transient Duration
vs Comparator Overdrive (V1, V2)

450

400

350

300

250

200

150

100

TYPICAL TRANSIENT DURATION (µs)

50

0

80

60

100

2902 G13

0.1

RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V

RESET OCCURS
ABOVE CURVE

1 10 100

TA = 25°C

2902 G14

RTX

Reset Time-Out Period
vs Temperature

8.9
CRT = 1500pF

(SILVER MICA)

8.4

(ms)

7.9

RST

7.4

6.9

6.4

5.9

RESET TIME-OUT PERIOD, t

5.4

2902 G15

4.9

–60

–40 0

–20

TEMPERATURE (°C)

20

40

80

60

100

2902 G16

Typical Transient Duration
vs Comparator Overdrive (V3, V4)

220
200
180
160
140
120
100

80
60

40

TYPICAL TRANSIENT DURATION (µs)

20

0

0.1

RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V

)

RESET OCCURS

ABOVE CURVE

1 10 100

Reset Time-Out Period
vs Capacitance

10

TA = 25°C

1

(sec)

RST

100m

10m

1m

RESET TIME-OUT PERIOD, t

100µ

10p 100p 10n 1µ

1n

CRT (FARAD)

TA = 25°C

2902 G25

100n

2902 G17

RTX

)

RST, COMPX I
vs Supply Voltage

10

TA = 25°C

9
8
7
6

(mA)

5

SINK

I

4
3
2
1
0

0

6

1

SINK

34

2

V1 OR V2 (V)

VOL = 0.4V

VOL = 0.2V

5

2902 G18

RST High Level Output Voltage
RST, COMPX Voltage Output Low
vs Output Sink Current

3.0
V2 = 3V

V1 = 5V

2.5

2.0

(V)

1.5

OL

V

1.0

0.5

6

0

0

10 30

85°C

20

40

I

(mA)

SINK

25°C

–40°C

70

50 90

60

80

2902 G19

vs Output Source Current
(LTC2902-2)

3.5

3.0

2.5

2.0

(V)

OH

V

1.5

1.0

0.5

0

0 0.5 2

85°C

I

SOURCE

1.51

(mA)

V1 = 5V
V2 = 3V
V3 = 2.5V
V4 = 1V

–40°C

25°C

2.5

2902 G20

2902f

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2902

COMPX Pull-Up Current
vs V2 (COMPX Held at 0V)

20

TA = 25°C

18
16
14

12

10

8
6

PULL-UP CURRENT (µA)

4
2

0

1

1.5 2.5

2

V2 (V)

RST Pull-Up Current vs V2
(LTC2902-1)

20

TA = 25°C

18
16
14
12
10

8

V

RT25

2.5

V

RT30

V

RT33

3

3.5 4

V2 (V)

6

PULL-UP CURRENT (µA)

4
2
0

2

COMPX Propagation Delay vs
Input Overdrive Above Threshold

250

200

150

100

V1, V2

50

COMPX PROPAGATION DELAY (µs)

3.5

4

5

2902 G21

3

4.5

0

10 100

INPUT OVERDRIVE ABOVE THRESHOLD (mV)

V3, V4

TA = 25°C

1000

2902 G22

RST Pull-Up Current vs V2
(LTC2902-2)

6

TA = 25°C

5

4

3

V

RT25

2.5

V

RT30

RT33

3

3.5 4

V2 (V)

4.5

5

2902 G24

4.5

2902 G23

2

PULL-UP CURRENT (mA)

V

1

0

5

2

U

UU

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. See Table 1 for details.

V1 (Pin 4): Voltage Input 1. Select from 5V or 3.3V. See
Table 1 for details. The greater of (V1, V2) is also VCC for
the chip. Bypass this pin to ground with a 0.1µF (or
greater) capacitor.

CRT (Pin 5): Reset Delay Time Programming Pin. Attach
an external capacitor (CRT) to GND to set a reset delay time
of 4.6ms/nF. Leaving the pin open generates a minimum
delay of approximately 50µs. A 47nF capacitor will gener-
ate a 216ms reset delay time.

2902f

7

LTC2902

U

UU

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). See Applications Information for tolerance selec­tion chart (Table 4).

RDIS (Pin 8): Digital Input for RST Disable. A low input on
this pin forces the RST output to V2 (or pull-up voltage).
Useful for determining supply margins without issuing
reset command to processor. A weak internal pull-up
allows pin to be left floating for normal monitor operation.

T1 (Pin 9): Digital Input for Supply Tolerance Selection
(5%, 7.5%, 10% or 12.5%). Used in conjunction with T0
(Pin 7). See Applications Information for tolerance selec­tion chart (Table 4).

GND (Pin 10): Ground.
VPG (Pin 11):

Input. Connect to an external 1% resistive divider be­tween V
preset and/or ±adjustable voltage thresholds (see Table␣ 1).
Do not add capacitance on the VPG pin.

REF

Voltage Threshold Combination Select

and GND to select 1 of 16 combinations of

V

(Pin 12): Buffered Reference Voltage. A 1.210V

REF

nominal reference used for programming voltage (VPG)
and for the offset of negative adjustable applications. The
buffered reference can source and sink up to 1mA. The
reference can drive a bypass capacitor of up to 1000pF
without oscillation.

V4 (Pin 13): Voltage Input 4. Select from 1.8V, 1.5V, ADJ
or –ADJ. See Table 1 for details.

V2 (Pin 14): Voltage Input 2. Select from 3.3V, 3V or 2.5V.
See Table 1 for details. The greater of (V1, V2) is also V
for chip. Bypass this pin to ground with a 0.1µF (or greater)
capacitor. All logic outputs (COMP1, COMP2, COMP3,
COMP4) are weakly pulled up to V2. RST is weakly pulled
up to V2 in the LTC2902-1 and RST is actively pulled up to
V2 in the LTC2902-2.

COMP4 (Pin 15): Comparator Output 4. Nondelayed,
active high logic output with weak pull-up to V2. Pulls high
when V4 is above reset threshold. May be pulled greater
than V2 using external pull-up.

COMP2 (Pin 16): Comparator Output 2. Nondelayed,
active high logic output with weak pull-up to V2. Pulls high
when V2 is above reset threshold. May be pulled greater
than V2 using external pull-up.

CC

8

2902f

BLOCK DIAGRA

W

V1

POWER
DETECT

LTC2902

V2

V

CC

6µA

V1

V2
14

V3

V4
13

GND

10

V

11

V

REF

12

–

V2

COMP1

2

+

V2

–

4

+

RESISTIVE

DIVIDER

3

MATRIX

–

6µA

COMP2

16

V2

+

6µA

–

PG

A/D

BUFFER

+

BANDGAP

REFERENCE

COMP3

1

V2

6µA

COMP4

15

BUFFER

GAIN

ADJUST

T0

7

ADJUSTABLE
RESET PULSE

GENERATOR

22µA

T1

9

CRT

5

C

RT

V

CC

2µA

10µA

V

CC

RDIS

8

V2

LTC2902-1

6µA

LTC2902-2

V2

RST

6

RST

6

2902 DB-1

2902f

9

LTC2902

WUUU

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. Once all the VX inputs
rise above their thresholds, an internal timer is started
and RST is released after the programmed delay time. If
VCC < (V3 – 1) and VCC < 2.4V, the V3 input impedance
will be low (1kΩ typ).

Monitor Programming

The LTC2902 input voltage combination is selected by
placing the recommended resistor divider from V
GND and connecting the tap point to VPG, as shown in
Figure 4. Table 1 offers recommended 1% resistor values
for the various modes. The last column in Table 1 speci­fies optimum VPG/V
pro

gramming with a ratiometric DAC.

ratios (±0.01) to be used when

REF

During power-up, once V1 or V2 reaches 2.4V (max), the
monitor enters a programming period of approximately
150µs during which the voltage on the VPG pin is sampled
and the monitor is configured to the desired input combi­nation. Do not add capacitance to the VPG pin. Immediately
after programming, the comparators are enabled and
supply monitoring will begin.

Supply Monitoring

The LTC2902 is a low power, high accuracy program­mable quad supply monitoring circuit with four nondelayed
monitor outputs, a common reset output and selectable
supply thresholds. Reset timing is adjustable using an
external capacitor. Single pin programming selects 1 of 16
input voltage monitor combinations. Two digital inputs
select one of four supply tolerances (5%, 7.5%, 10% or

12.5%). All four voltage inputs must be above predeter­mined thresholds for the reset not to be invoked. The
LTC2902 will assert the reset and comparator outputs
during power-up, power-down and brownout conditions
on any one of the voltage inputs.

REF

to

LTC2902

V

REF

V

PG

GND

Figure 4. Monitor Programming

Table 1. Voltage Threshold Programming

MODE V1 (V) V2 (V) V3 (V) V4 (V) R1 (kΩ) R2 (kΩ)V

0 5.0 3.3 ADJ ADJ Open Short 0.000
1 5.0 3.3 ADJ –ADJ 93.1 9.53 0.094
2 3.3 2.5 ADJ ADJ 86.6 16.2 0.156
3 3.3 2.5 ADJ –ADJ 78.7 22.1 0.219
4 3.3 2.5 1.5 ADJ 71.5 28.0 0.281
5 5.0 3.3 2.5 ADJ 66.5 34.8 0.344
6 5.0 3.3 2.5 1.8 59.0 40.2 0.406
7 5.0 3.3 2.5 1.5 53.6 47.5 0.469
8 5.0 3.0 2.5 ADJ 47.5 53.6 0.531

9 5.0 3.0 ADJ ADJ 40.2 59.0 0.594
10 3.3 2.5 1.8 1.5 34.8 66.5 0.656
11 3.3 2.5 1.8 ADJ 28.0 71.5 0.719
12 3.3 2.5 1.8 –ADJ 22.1 78.7 0.781
13 5.0 3.3 1.8 –ADJ 16.2 86.6 0.844
14 5.0 3.3 1.8 ADJ 9.53 93.1 0.906
15 5.0 3.0 1.8 ADJ Short Open 1.000

R1
1%

12
11
10

R2
1%

2902 F04

V

PG

REF

The inverting inputs on the V3 and/or V4 comparators are
set to 0.5V when the positive adjustable modes are selected
and with T0 and T1 low (5% tolerance) (Figure 5). The tap
point on an external resistive divider, connected between
the positive voltage being sensed and ground, is connected
to the high impedance noninverting inputs (V3, V4). The
trip voltage is calculated from:

R

3

VV

=+

TRIP



05 1

.










R

4

Once the resistor divider is set in the 5% tolerance mode,
there is no need to change the divider for the other
tolerance modes (7.5%, 10%, 12.5%) because the inter­nal reference is scaled accordingly, moving the trip point
in –2.5% increments.

10

2902f

WUUU

APPLICATIO S I FOR ATIO

LTC2902

V

TRIP

R3

V3 OR V4

Figure 5. Setting the Positive Adjustable Trip Point

Figure 6. Setting the Negative Adjustable Trip Point

1%

R4
1%

12

V
R4
1%

R3
1%

V

TRIP

REF

V4

13

LTC2902

+

–

0.5V

+
–

5% TOLERANCE MODE

LTC2902

–

+

2902 F05

2902 F06

In the negative adjustable mode, the noninverting input on
the V4 comparator is connected to ground (Figure 6). The
tap point on an external resistive divider, connected be­tween the negative voltage being sensed and the V

REF

pin,
is connected to the high impedance inverting input (V4).
V

provides the necessary level shift required to operate

REF

at ground. The trip voltage is calculated from:

R

3



VV

=

TRIP REF REF



VV

=–;.









R

4

1 210

Table 2. Suggested 1% Resistor Values for the ADJ Inputs

V

(V) V

SUPPLY

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 1.685 237 100

1.5 1.410 182 100

1.2 1.120 124 100
1 0.933 86.6 100

0.9 0.840 68.1 100

Table 3. Suggested 1% Resistor Values for the –ADJ Input

V

(V) V

SUPPLY

–2 –1.87 187 121
–5 –4.64 464 121

–5.2 –4.87 487 121

–10 –9.31 931 121
–12 –11.30 1130 121

(V) R3 (kΩ) R4 (kΩ)

TRIP

(V) R3 (kΩ) R4 (kΩ)

TRIP

Although all four supply monitor comparators have built-in
glitch immunity, bypass capacitors on V1 and V2 are
recommended because the greater of V1 or V2 is also the
VCC for the chip. Filter capacitors on the V3 and V4 inputs
are allowed.

T0,T1 Low (5% Tolerance Mode)

Once the resistor divider is set in the 5% tolerance mode,
there is no need to change the divider for the other
tolerance modes (7.5%, 10%, 12.5%) because V

REF

is
scaled accordingly, moving the trip point in –2.5%
increments.

In a negative adjustable application, the minimum value
for R4 is limited by the sourcing capability of V
With no other load on V

, R4 (minimum) is:

REF

( ±1mA).

REF

1.21V ÷ 1mA = 1.21kΩ

Tables 2 and 3 offer suggested 1% resistor values for
various adjustable applications.

Power-Down

On power-down, once any of the VX inputs drop below
their threshold, RST and COMPX are held at a logic low.
A logic low of 0.4V is guaranteed until both V1 and V2
drop below 1V. If the bandgap reference becomes invalid
(VCC < 2V typ), the part will reprogram once VCC rises
above 2.4V (max).

Monitor Output Rise and Fall Time Estimation

All of the outputs (RST, COMPX) have strong pull-down
capability. If the external load capacitance (C

LOAD

) for a

2902f

11

LTC2902

WUUU

APPLICATIO S I FOR ATIO

particular output is known, output fall time (10% to 90%)
is estimated using:

t

≈ 2.2 • RPD • C

FALL

LOAD

where RPD is the on-resistance of the internal pull-down
transistor. The typical performance curve (VOL vs I

SINK

)

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.

Although the outputs are considered to be “open-drain,”
they do have a weak pull-up capability (see COMPX or RST
Pull-Up Current vs V2 curve). Output rise time (10% to
90%) is estimated using:

t

≈ 2.2 • RPU • C

RISE

LOAD

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:

5

610

R

PU

•

=Ω

V

21

–

with V2 = 3.3V, RPU is about 260k. Using 150pF for load
capacitance, the rise time is 86µs. If the output needs to
pull up faster and/or to a higher voltage, a smaller
external pull-up resistor may be used. Using a 10k pull­up resistor, the rise time is reduced to 3.3µs for a 150pF
load capacitance.

The LTC2902-2 has an active pull-up to V2 on the RST
output. The typical performance curve (RST Pull-Up Cur­rent vs V2 curve) demonstrates that the pull-up current is
somewhat linear versus the V2 voltage and RPU is esti­mated to be approximately 625Ω. A 150pF load capaci­tance makes the rise time about 206ns.

Selecting the Reset Timing Capacitor

The reset time-out period is adjustable in order to accom­modate a variety of microprocessor applications. The
reset time-out period, t

, is adjusted by connecting a

RST

capacitor, CRT, between the CRT pin and ground. The value
of this capacitor is determined by:

CRT = t

• 217 • 10

RST

–9

with CRT in Farads and t

in seconds. The CRT value per

RST

millisecond of delay can also be expressed as CRT/ms =
217 (pF/ms).

Leaving the CRT pin unconnected will generate a mini­mum reset time-out of approximately 50µs. Maximum
reset time-out is limited by the largest available low
leakage capacitor. The accuracy of the time-out period will
be affected by capacitor leakage (the nominal charging
current is 2µA) and capacitor tolerance. A low leakage
ceramic capacitor is recommended.

Tolerance Programming and the RESET Disable

Using the two digital inputs T0 and T1, the user can
program the global supply tolerance for the LTC2902 (5%,

7.5%, 10%, 12.5%). The larger tolerances provide more
headroom by lowering the trip thresholds.

Table 4. Tolerance Programming

T0 T1 TOLERANCE (%) V

Low Low 5 1.210
Low High 7.5 1.178
High Low 10 1.146
High High 12.5 1.113

REF

(V)

Under conventional operation, RST and COMPX will go
low when VX is below its threshold. At any time, the RDIS
pin can be pulled low, overriding the reset operation and
forcing the RST pin high. This feature is useful when
determining supply margins under processor control since
the reset command will not be invoked. The RDIS pin is
connected to a weak internal pull-up to VCC (10µA typ),
allowing the pin to be left floating if unused.

Ensuring RST Valid for VCC Down to 0V (LTC2902-2)

When VCC is below 1V the RST pull-down capability is
drastically reduced. The RST pin may float to undeter­mined voltages when connected to high impedance (such
as CMOS logic inputs). The addition of a pull-down resis­tor from RST to ground will provide a path for stray charge
and/or leakage currents. The resistor value should be
small enough to provide effective pull-down without ex­cessively loading the pull-up circuitry. Too large a value
may not pull down well enough. A 100k resistor from RST
to ground is satisfactory for most applications.

2902f

12

U

TYPICAL APPLICATIO S

LTC2902

Quad Supply Monitor, 5% Tolerance

5V, 3V, 1.8V, 12V (ADJ)

1

COMP3

2

COMP1

1.8V 3V

SYSTEM

RESET

C

RT

3

V3

4

5V

LTC2902

V1

5

CRT

6

RST

7

T0

8

RDIS

COMP2
COMP4

V

REF

V

GND

16
15
14

V2

13

V4

12
11

PG

10
9

T1

R3

2.15M
1%

R4
100k
1%

2902 TA02

5V, –5V Monitor with Unused V2, V3 Inputs Pulled

Above Trip Thresholds (5% Tolerance)

COMP2
COMP4

V

REF

V

GND

16
15
14

V2

13

V4

12
11

PG

10
9

T1

R1

16.2k
1%

R2

86.6k
1%

2902 TA03

5V

SYSTEM

RESET
C

RT

1
2
3
4
5
6
7
8

COMP3
COMP1
V3

LTC2902

V1
CRT
RST
T0
RDIS

R4

121k

1%

12V

V

TRIP

= 11.25V

R3

464k

1%

–5V

V

TRIP

= –4.64V

2902f

13

LTC2902

TYPICAL APPLICATIO S

Quad Supply Monitor with LED Undervoltage Indicators,

U

12.5% Tolerance, Reset Disabled
5V, 3.3V, 2.5V, 1.5V

L1

LED

R
1k

LED

1
2
3
4
5
6
7
8

L3

COMP3
COMP1
V3
V1
CRT
RST
T0
RDIS

LTC2902

COMP2
COMP4

V

REF

V

GND

V2
V4

PG

T1

R
1k

2.5V

5V

C

RT

R
1k

16
15
14
13
12
11
10
9

L2

LED

2902 TA04

R
1k

3.3V

1.5V

R1

53.6k
1%

R2

47.5k
1%

L4

LED

14

2902f

PACKAGE DESCRIPTIO

LTC2902

U

GN Package

16-Lead Plastic SSOP (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1641)

.045 ±.005

.254 MIN

RECOMMENDED SOLDER PAD LAYOUT

.007 – .0098

(0.178 – 0.249)

.016 – .050

NOTE:

1. CONTROLLING DIMENSION: INCHES

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

(0.406 – 1.270)

INCHES

(MILLIMETERS)

.150 – .165

.0250 TYP.0165 ±.0015

.015

(0.38 ± 0.10)

0° – 8° TYP

± .004

× 45°

.229 – .244

(5.817 – 6.198)

.053 – .068

(1.351 – 1.727)

.008 – .012

(0.203 – 0.305)

16

15

12

.189 – .196*

(4.801 – 4.978)

12 11 10

14

13

5

4

3

678

9

(0.102 – 0.249)

.0250

(0.635)

BSC

(0.229)

.150 – .157**
(3.810 – 3.988)

.004 – .0098

GN16 (SSOP) 0502

.009

REF

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

2902f

15

LTC2902

TYPICAL APPLICATIO

U

Quad Supply Monitor with Hysteresis

5% Tolerance (Supplies Rising)

12.5% Tolerance (After RST Goes High)

5V

3.3V

2.5V

1.8V

R1
59k
1%

R2

40.2k
1%

LTC2902-1

4

V1

14

V2

3

V3

13

V4

8

RDIS

12

V

REF

11

V

PG

10

GND

COMP1
COMP2
COMP3
COMP4

RST

CRT

T0
T1

2
16
1
15
6
7
9
5

2902 TA05

10k

C

RT

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Linear Technology Corporation

16

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear.com

Timing Specifications

FAIL

LT/TP 1002 2K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2002

2902f