MAXIM MAX793, MAX794, MAX795 User Manual

General Description

The MAX793/MAX794/MAX795 microprocessor (µP) supervisory circuits monitor and control the activities of +3.0V/+3.3V µPs by providing backup-battery switchover, among other features such as low-line indication, µP reset, write protection for CMOS RAM, and a watchdog (see the

Selector Guide

below). The backup-battery voltage can exceed VCC, permitting the use of 3.6V lithium batteries in systems using 3.0V to 3.3V for VCC.

The MAX793/MAX795 offer a choice of reset threshold voltage range (denoted by suffix letter): 3.00V to 3.15V (T), 2.85V to 3.00V (S), and 2.55V to 2.70V (R). The MAX794’s reset threshold is set externally with a resistor divider. The MAX793/MAX794 are available in 16-pin DIP and narrow SO packages, and the MAX795 comes in 8-pin DIP and SO packages.

________________________Applications

Battery-Powered Computers and Controllers

Embedded Controllers

Intelligent Controllers

Critical µP Power Monitoring

Portable Equipment

____________________________Features

MAX793/MAX794/MAX795 o Precision Supply-Voltage Monitor:

Fixed Reset Trip Voltage (MAX793/MAX795) Adjustable Reset Trip Voltage (MAX794)

o Guaranteed Reset Assertion to VCC= 1V o Backup-Battery Power Switching—Battery

Voltage Can Exceed V

CC

o On-Board Gating of Chip-Enable Signals—7ns

Max Propagation Delay

MAX793/MAX794 Only

o Battery Freshness Seal o Battery OK Output (MAX793) o Uncommitted Voltage Monitor for Power-Fail or

Low-Battery Warning

o Independent Watchdog Timer (1.6s timeout) o Manual Reset Input

MAX793/MAX794/MAX795

3.0V/3.3V Adjustable Microprocessor Supervisory Circuits

________________________________________________________________

Maxim Integrated Products

1

19-0366; Rev 6; 3/10

FEATURE

Active-Low Reset

Active-High Reset

Programmable Reset Threshold

Low-Line Early Warning Output

MAX793



MAX794



MAX795



Backup-Battery Switchover

External Switch Driver

Power-Fail Comparator



Battery OK Output



_____________________Selector Guide

__________Typical Operating Circuit

Watchdog Input

Battery Freshness Seal



Manual Reset Input



Chip-Enable Gating

 

Pin-Package 16-DIP/SO 16-DIP/SO 8-DIP/SO

Pin Configurations appear at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

Ordering Information continued at end of data sheet.

*

The MAX793/MAX795 offer a choice of reset threshold voltage. Select the letter corresponding to the desired reset threshold voltage range (T = 3.00V to 3.15V, S = 2.85V to 3.00V, R =

2.55V to 2.70V) and insert it into the blank to complete the part number. The MAX794’s reset threshold is adjustable.

Devices are available in both leaded and lead-free packaging. Specify lead free by adding the + symbol at the end of the part number when ordering.

PART* TEMP RANGE

MAX793_CPE 0°C to +70°C 16 Plastic DIP

MAX793_CSE 0°C to +70°C 16 Narrow SO

PINPACKAGE

(OPTIONAL)

V

CC

BATT

WDO

MR

PFO

PFI

Si9433DY

SILICONIX

PMOS

BATT ON

MAX793

LOWLINE

GND

OUT

CE OUT

CE IN

WDI

RESET

BATT OK

0.1µF

CMOS

RAM

ADDRESS DECODER

V

CC

V

CC

A0-A15

I/O NMI

µP

RESET

3.6V

3.0V OR 3.3V

+5V SUPPLY

FAILURE

+5V

0.1µF

µA

MAX793/MAX794/MAX795

3.0V/3.3V Adjustable Microprocessor Supervisory Circuits

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= 3.17V to 5.5V for the MAX793T/MAX795T, VCC= 3.02V to 5.5V for the MAX793S/MAX795S, VCC= 2.72V to 5.5V for the MAX793R/MAX794/MAX795R, V

BATT

= 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Terminal Voltage (with respect to GND)

V

CC

......................................................................-0.3V to +6.0V

V

BATT

...................................................................-0.3V to +6.0V

All Other Inputs ..................-0.3V to the higher of V

CC

or V

BATT

Continuous Input Current

V

CC

.................................................................................200mA

V

BATT

................................................................................50mA

GND ..................................................................................20mA

Output Current

V

OUT

................................................................................200mA

All Other Outputs ..............................................................20mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) .....727mW

8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW

16-Pin Plastic DIP (derate 10.53mW/°C above +70°C) .842mW 16-Pin Narrow SO (derate 9.52mW/°C above +70°C) ...696mW

Operating Temperature Ranges

MAX793_C_ _/MAX794C_ _/MAX795_C_ _ ......... 0°C to +70°C

MAX793_E_ _/MAX794E_ _/MAX795_E_ _ ........-40°C to +85°C

Storage Temperature Range .............................-65°C to +160°C

Lead Temperature (soldering, 10s) .................................+300°C

Soldering Temperature (reflow) .......................................+260°C

MAX79_E

MAX79_C

V

BATT

> V

CC

(Note 6)

I

OUT

= 250µA (Note 4)

I

OUT

= 30mA (Note 4)

VSW> VCC> 1.75V (Note 5)

I

OUT

= 75mA

V

BATT

= 2.3V

CONDITIONS

Battery Switch Threshold (V

CC

falling)

V

2.30 2.41 2.52

V

SW

2.55 2.68 2.80

2.69 2.82 2.95

mV20 65

VCC-

V

BATT

V

BATT

- 0.14

V

OUT

OUT Output Voltage in Battery-Backup Mode

V

BATT

- 0.1 V

BATT

- 0.034

V

1.1 5.5

1.0 5.5

Operating Voltage Range, V

CC

, V

BATT

(Note 1)

V

VCC- 0.001 VCC- 0.5mV

V

OUT

OUT Output Voltage in Normal Mode

VCC- 0.12 VCC- 0.050

VCC- 0.3 VCC- 0.125

µA0.5

Battery Leakage Current (Note 3)

µA1

BATT Supply Current (excluding I

OUT

) (Note 2)

UNITSMIN TYP MAXSYMBOLPARAMETER

VCC= 0V, V

OUT

= 0V µA1

BATT Leakage Current, Freshness Seal Enabled

I

OUT

= 250µA

I

OUT

= 1mA

MAX793T/MAX795T MAX793S/MAX795S

This value is identical to the reset threshold, VCCrising for V

BATT

> V

RST

VCC-

V

BATT

MAX793R/MAX795R/ MAX794

V

BATT

< V

RST

mV25 65

Battery Switch Threshold (V

CC

rising) (Note 7)

MAX793/MAX794, MR = V

CC

µA

62 80

I

SUPPLY

46 60

VCCSupply Current (excluding I

OUT

, I

CE OUT

)

VCC= 2.1V, V

BATT

= 2.3V

µA

32 45

I

SUPPLY

VCCSupply Current in Battery-Backup Mode (excluding I

OUT

)

VCC< 3.6V

VCC< 5.5V

MAX793/MAX794

MAX795 24 35

MAX795

49 70

35 50VCC< 3.6V

VCC< 5.5V

MAX793/MAX794/MAX795

3.0V/3.3V Adjustable Microprocessor Supervisory Circuits

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.17V to 5.5V for the MAX793T/MAX795T, VCC= 3.02V to 5.5V for the MAX793S/MAX795S, VCC= 2.72V to 5.5V for the MAX793R/MAX794/MAX795R, V

BATT

= 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

CONDITIONS

2.85 2.925 3.00

3.00 3.075 3.15

UNITSMIN TYP MAXSYMBOLPARAMETER

VCCfalling

3.00 3.085 3.17

2.55 2.625 2.70

V

RST

V

RST IN

V

VCCfalling

VCCrising

RESET IN Threshold (MAX794 only)

1.212 1.240 1.262

Reset Threshold (Note 8)

2.55 2.635 2.72

2.85 2.935 3.02

V

LR

mV

MAX793

LOWLINE-to-Reset Threshold, (V

LOWLINE

-

V

RST

), VCCFalling

VCC< 3.6V

51525

30 45 60

mV

MAX793S/MAX795S

MAX793T/MAX795T

MAX794

MAX793

3.08

Low-Line Comparator Hysteresis

3.23

mV

10

mst

RP

140 200 280Reset Timeout Period

V

MAX793R/MAX795R 2.78

nA

V

PFI

rising

V

PFI

falling

PFI Input Current

MAX794

V

-25 2 25

V

TH

1.212 1.250 1.287

PFI Input Threshold

1.212 1.240 1.262

V

LL

1.317

LOWLINE Threshold, V

CC

Rising

VV

BOK

2.00 2.25 2.50

BATT OK Threshold (MAX793)

V

OH

VI

SOURCE

= 300µA, VCC= V

RST

max

BATT OK, BATT ON, WDO, LOWLINE Output-Voltage High

I

SOURCE

= 300µA, VCC= V

RST

min

0.8V

CC

0.86V

CC

VV

OH

0.8V

CC

0.86V

CC

RESET Output-Voltage High

mV10 20PFI Hysteresis, PFI Rising

MAX793T/MAX795T

MAX793S/MAX795S

MAX793R/MAX795R

MAX793T/MAX795T

MAX793S/MAX795S

MAX793R/MAX795R

nA

RESET IN Leakage Current (MAX794 only)

-25 2 25

MAX794

V

OH

VI

SOURCE

= 65µA, VCC= V

RST

max

PFO Output-Voltage High

0.8V

CC

V

OH

VI

SOURCE

= 100µA, VCC= 2.3V, V

BATT

= 3V

BATT ON OutputVoltage High

0.8V

BATT

I

LEAK

µAVCC= V

RST

max

RESET Output Leakage Current (Note 9)

-1 -1

I

SC

µAVCC= 3.3V, V

PFO

= 0V

PFO Output Short to GND Current

180 500

V

OL

V

I

SINK

= 1.2mA; RESET, LOWLINE tested

with V

CC

= V

RST

min; RESET, BATTOK,

WDO tested with V

CC

= V

RST

max

PFO, RESET, RESET, WDO, LOWLINE Output-Voltage

Low

0.08 0.2V

CC

INPUT AND OUTPUT LEVELS

VCCrising 1.212 1.250 1.282

MAX793/MAX794/MAX795

3.0V/3.3V Adjustable Microprocessor Supervisory Circuits

4 _______________________________________________________________________________________

CONDITIONS

V

OL

V

OL

VI

SINK

= 3.2mA, VCC= V

RST

max

MAX79_E, V

BATT

= VCC= 1.2V, I

SINK

= 200µA

BATT ON OutputVoltage Low

MAX79_C, V

BATT

= VCC= 1.0V, I

SINK

= 40µA

0.2V

CC

RESET Output-Voltage Low

UNITSMIN TYP MAXSYMBOLPARAMETER

V

IL

V

t

MR

nsMAX793/MAX794 only

V

RST

max < VCC< 5.5V

MR Pulse Width

100

All Inputs Including PFO (Note 10)

0.3V

CC

V

IH

0.7V

CC

0.17 0.3

0.13 0.3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.17V to 5.5V for the MAX793T/MAX795T, VCC= 3.02V to 5.5V for the MAX793S/MAX795S, VCC= 2.72V to 5.5V for the MAX793R/MAX794/MAX795R, V

BATT

= 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

t

MD

ns

MAX793/MAX794 only, MR = 0V

MAX793/MAX794 only

µA

MR-to-Reset Delay

25 70 250

MR Pullup Current

75 250

Ω

nsVCC= V

RST

max, Figure 9

Enable mode, VCC= V

RST

max

CE IN-to-CE OUT Propagation Delay

Disable mode

27

CE IN-to-CE OUT Resistance

V

OH

V

OL

V

VCC= V

RST

max, I

OUT

= 1.6mA,

V

CE IN

= 0V

VCC= V

RST

max, I

OUT

= -1mA,

V

CE IN

= V

CC

CE OUT Drive from CE IN

0.2V

CC

0.8V

CC

nA

46

I

LEAK

±10

CE IN Leakage Current

Note 1: VCCsupply current, logic-input leakage, watchdog functionality (MAX793/MAX794), MR functionality (MAX793/MAX794),

PFI functionality (MAX793/MAX794), and state of RESET and RESET (MAX793/MAX794) tested at V

BATT

= 3.6V and VCC=

5.5V. The state of RESET is tested at V

CC

= VCCmin.

Note 2: Tested at V

BATT

= 3.6V, VCC= 3.5V and 0V. The battery current rises to 10µA over a narrow transition window around V

CC

= 1.9V.

Note 3: Leakage current into the battery is tested under the worst-case conditions at V

CC

= 5.5V, V

BATT

= 1.8V and VCC= 1.5V,

V

BATT

= 1.0V.

Note 4: Guaranteed by design. Note 5: When V

SW

> VCC> V

BATT

, OUT remains connected to VCCuntil VCCdrops below V

BATT

. The VCC-to-V

BATT

comparator

has a small 15mV typical hysteresis to prevent oscillation. For V

CC

< 1.75V (typical), OUT switches to BATT regardless of

V

BATT

.

Note 6: When V

BATT

> VCC> VSW, OUT remains connected to VCCuntil VCCdrops below the battery switch threshold (VSW).

Note 7: OUT switches from BATT to V

CC

when VCCrises above the reset threshold, if V

BATT

> V

RST

. In this case, switchover back

to V

CC

occurs at the exact voltage that causes reset to be asserted, however, switchover occurs 200ms prior to reset. If

V

BATT

< V

RST

, OUT switches from BATT to VCCwhen VCCexceeds V

BATT

.

Note 8: The reset threshold tolerance is wider for V

CC

rising than for VCCfalling to accommodate the 10mV typical hysteresis,

which prevents internal oscillation.

Note 9: The leakage current into or out of the RESET pin is tested with RESET not asserted (RESET output high impedance). Note 10: PFO is normally an output, but is used as an input when activating the battery freshness seal.

µs10

Reset to CE OUT High Delay

t

WD

s

0V < VCC< 5.5V

Watchdog Timeout Period

IOH= 500µA, VCC< 2.3V

µA

1.00 1.60 2.25

-1 0.01 1WDI Input Current

VV

OH

0.8V

BATT

CE OUT Output-Voltage High (reset active)

nsWDI Pulse Width 100

MANUAL RESET INPUT

CHIP-ENABLE GATING

WATCHDOG (MAX793/MAX794 only)

MAX793/MAX794/MAX795

3.0V/3.3V/Adjustable Microprocessor Supervisory Circuits

_______________________________________________________________________________________

5

__________________________________________Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

VCC-TO-OUT ON-RESISTANCE

vs. TEMPERATURE

3.0

2.8

2.6

2.4

2.2 VCC = 3.0V

2.0

1.8

1.6

-TO-OUT ON-RESISTANCE (Ω)

CC

1.4

V

1.2

1.0

-40 100

VCC = 5V

20-20 0 8040 60

TEMPERATURE (°C)

BATTERY SUPPLY CURRENT vs.

TEMPERATURE (BATTERY-BACKUP MODE)

0.10

0.08

0.06

0.04

SUPPLY CURRENT (µA)

0.02

0

-40 100

20-20 0 8040 60

TEMPERATURE (°C)

MAX793

LOWLINE-TO-RESET THRESHOLD

vs. TEMPERATURE

100

90

80

70

60

50

40

30

20

LOWLINE-TO-RESET THRESHOLD (mV)

10

0

-40 100

20-20 0 8040 60

TEMPERATURE (°C)

I

= 30mA

OUT

VCC = 3.3V

VCC = 0V

= 3.6V

V

BATT

VCC FALLING

MAX793 TOC1

100

BATT-TO-OUT ON-RESISTANCE (Ω)

MAX793 TOC4

RESET TIMEOUT PERIOD (ms)

MAX793 TOC7

PROPAGATION DELAY (µs)

BATT-TO-OUT ON-RESISTANCE

vs. TEMPERATURE

160

140

120

V

= 3.6V

BATT

80

60

40

-40 100

V

= 3.0V

BATT

V

= 5V

BATT

20-20 0 8040 60

TEMPERATURE (°C)

I

OUT

V

CC

= 250µA = 0V

RESET TIMEOUT PERIOD

vs. TEMPERATURE

250

200

150

100

50

0

-40 100 TEMPERATURE (°C)

VCC RISING FROM OV TO V

20-20 0 8040 60

MAX

RST

MAX793/MAX794

LOWLINE COMPARATOR PROPAGATION DELAY

vs. TEMPERATURE

10

8

6

4

2

0

VCC RISING

VCC FALLING

-40 100

40mV OVERDRIVE

20-20 0 8040 60

TEMPERATURE (°C)

MAX793 TOC2

MAX793 TOC5

MAX793 TOC8

VCC SUPPLY CURRENT vs. TEMPERATURE

(NORMAL OPERATING MODE)

70

60

MAX795, VCC = 5V

50

40

30

SUPPLY CURRENT (µA)

20

CC

V

10

0

MAX795, VCC = 3.3V

-40 100

MAX793/4, VCC = 5V

MAX793/4, VCC = 3.3V

V

= VCC = V

BATT

20-20 0 8040 60

TEMPERATURE (°C)

RESET COMPARATOR PROPAGATION DELAY

vs. TEMPERATURE (V

30

25

20

15

10

PROPAGATION DELAY (µs)

5

0

-40 100

20-20 0 8040 60

TEMPERATURE (°C)

FALLING)

CC

MAX793/MAX794

PFI THRESHOLD vs. TEMPERATURE

1.250

1.245

1.240

PFI THRESHOLD (V)

1.235

1.230

-40 100

20-20 0 8040 60

TEMPERATURE (°C)

OUT

MAX793 TOC3

MAX793 TOC6

MAX793 TOC9

MAX793/MAX794/MAX795

3.0V/3.3V Adjustable Microprocessor Supervisory Circuits

6 _______________________________________________________________________________________

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

1.242

1.241

1.240

1.239

1.238

1.237

1.236

30

25

20

15

10

5

0

-40 100

MAX794

RESET IN THRESHOLD AND LOWLINE-TO-RESET IN

THRESHOLD vs. TEMPERATURE

TEMPERATURE (°C)

RESET IN THRESHOLD (V)

LOWLINE-TO-RESET IN THRESHOLD (mV)

20-20 0 8040 60

V

LOWLINE

- V

RST

V

RESET IN

VCC FALLING

MAX793 TOC10

2.5

2.0

1.5

1.0

0.5

0

-40 100

MAX793

BATT OK THRESHOLD vs. TEMPERATURE

MAX793 TOC11

TEMPERATURE (°C)

BATT OK THRESHOLD (V)

20-20 0 8040 60

V

BATT

FALLING

60

50

40

30

20

10

0

-40 100

CE IN-TO-CE OUT ON-RESISTANCE

vs. TEMPERATURE

TEMPERATURE (°C)

CE IN-TO-CE OUT ON-RESISTANCE (Ω)

20-20 0 8040 60

VCC = V

RST

MAX

MAX793 TOC12

1.70

1.65

1.60

1.55

1.50

-40 100

MAX793/MAX794

WATCHDOG TIMEOUT PERIOD

vs. TEMPERATURE

MAX793 TOC13

TEMPERATURE (°C)

WATCHDOG TIMEOUT PERIOD (sec)

20-20 0 8040 60

20

15

10

5

0

-40 100

MAX793/MAX794

BATTERY FRESHNESS SEAL

LEAKAGE CURRENT vs. TEMPERATURE

MAX793 TOC14

TEMPERATURE (°C)

LEAKAGE CURRENT (nA)

20-20 0 8040 60

V

BATT

= 5.5V

V

CC

= 0V

V

OUT

= 0V

1.002

1.001

1.000

0.999

0.998

0.997

0.996

-40 100

RESET THRESHOLD

vs. TEMPERATURE (NORMALIZED)

MAX793 TOC15

TEMPERATURE (°C)

V

RST

(NORMALIZED)

20-20 0 8040 60

VCC FALLING

10

8

6

4

2

0

-40 100

MAX793/MAX794

PFI TO PFO PROPAGATION DELAY

vs. TEMPERATURE

MAX793 TOC16

TEMPERATURE (°C)

PROPAGATION DELAY (µs)

20-20 0 8040 60

V

PFI

FALLING

20mV OVERDRIVE