SUMMIT SMS1242S, SMS1242S-A, SMS1242S-B, SMS1242S-C, SMS1242S-D Datasheet

SUMMIT

MICROELECTRONICS, Inc.	SMS1242

2.5V, 3V, 3.3V & 5V Dual Voltage, Dual Reset

Microprocessor Supervisory Circuits

FEATURES

•Supply voltage monitor

-Nominal VRST of 2.45V, 2.65V, 2.95V, 4.45V, 4.55V or 4.65V

-RESET# Outputs Guaranteed true at VCC = 1V

-150ms Reset Delay Time

•Second voltage monitor

-VSENSE Input

-1.25V threshold ±1%

•Manual Reset Input

•Includes 16k-bits nonvolatile memory

-Industry standard 2-wire serial interface

OVERVIEW

The SMS1242 microprocessor supervisory circuit reduces the complexity and number of components required to monitor the supply voltage in +5V, +3V and +2.5V systems. The SMS1242 will significantly improve system reliability and accuracy when compared to implementing the same functions with discrete components.

The SMS1242 provides reset output during power-up, power-down, and brown-out conditions. It has a 1.25V threshold input detector for power-fail warning, low battery detection, or monitoring a secondary power supply. The part also integrates a separate active low manual reset input.

It also has 16k-bits of nonvolatile memory accessible over an industry standard 2-wire serial interface.

FUNCTIONAL BLOCK DIAGRAM

SCL 6

SDA 5

VSENSE 3

VCC
8
		NONVOLATILE
		MEMORY
		ARRAY
+
–
		7	MR#
		2	RESET1#
+	VTRIP	RESET
–		GENERATOR
		1	RESET2#
1.25V
4

GND	2038 BD 2.0

© SUMMIT MICROELECTRONICS, Inc. 2000 •	300 Orchard City Drive, Suite 131 • Campbell, CA 95008 • Phone [phone]	• Fax [phone] • www.summitmicro.com
2038 2.0 6/8/00	Characteristics subject to change without notice	1

SMS1242

ABSOLUTE MAXIMUM RATINGS*

Temperature Under Bias	–55°C to 125°C
Storage Temperature	–65°C to 150°C
Terminal Voltage (With Respect to Ground)–0.3V to 6V
Lead Solder Temperature (10 secs)	300°C

*COMMENT

Stresses above 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 outside those listed in the operation sections of this specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability.

	Symbol	Parameter	Conditions		Min.	Typ.	Max.	Units
	VCC	Operating supply voltage			1		5.5	V
			3.6V < VCC < 5.5V			25	50	µA
	ICC	Supply current	3.6V > VCC			25	50	µA
			Memory access (SMS1243 only)				3	mA
			Device option	A	4.375	4.425	4.475	V
			Device option	B	4.625	4.675	4.725	V
	VRST	Reset threshold	Device option	C	4.425	4.475	4.525	V
			Device option	D	2.425	2.450	2.475	V
			Device option	E	2.625	2.650	2.675	V
			Device option	F	2.925	2.950	2.975	V
	VHYST	VRST Hysterisis				50		mV
	tRST	Reset pulse width			100	150	200	ms
	VOL	RESET1# output low voltage	ISINK = 1.2mA,	VCC = VRST min.			0.3	V
			ISINK = 200µA,	VCC = 1.2V			0.3	V
	IMR	MR# pullup current				100		µA
	tMR	MR# pulse width			50			ns
	VIL	MR# input threshold					0.6	V
	VIH	MR# input threshold			0.7 × VCC			V
	VSNS	VSENSE input threshold	VCC = VRST min., VSENSE falling		1.20	1.25	1.30	V
	VCC	RESET2# output low voltage	ISINK = 1.2mA,	VCC = VRST min.			0.3	V
			ISINK = 200µA,	VCC = 1.2V			0.4	V

2038 Elect Table 2.0

SUMMIT MICROELECTRONICS, Inc.

2038 2.0 6/8/00

2

SMS1242

PIN NAMES

PIN CONFIGURATION

8-Pin SOIC

Pin

Signal

Function

Active low output with weak pullup.

Driven low by: VSENSE below thresh-

RESET1#

1

8

VCC

1

RESET1#

old; or V below threshold while

MR# is below threshold. Remains

RESET2#

2

7

MR#

CC

low for 150ms after VSENSE, or VCC

VSENSE

3

6

SCL

and MR#, is above threshold.

GND

4

5

SDA

2

RESET2#

Same as Reset1#, except open

drain connection

2038 T PCon 2.0

3

VSENSE

Threshold detector input for the

Resets

4

GND

Ground

5

SDA/GND

SMS1243 Data I/O, or ground

6

SCL/GND

SMS1243 Data Clock, or ground

7

MR#

Manual input for Resets

8

VCC

Supply voltage

2038 Pin Table 2.0

VCC			VRST		VRST

tRST

RESET#

MR#

VIL

VIH

tRST

tRST

tMR

VSENSE

VSNS

2038 T Fig01 2.0

Figure 1. Reset Waveforms

2038 2.0 6/8/00

SUMMIT MICROELECTRONICS, Inc.

3

SMS1242

GLITCH AMPLITUDE (V)

4.5

4.4

4.3

4.2

4.1

4.0

3.9

3.8

0

1

2

3

4

5

6

7

8

9

10

PULSE WIDTH (ms)

2038 Fig02 2.0

Figure 2. Supply Voltage Noise Rejection, VRST =4.55V, TA = 25ºC

VRST

V

CC

0V

RESET#

0V

500ms/Div.

2V
1.25V	V
0V	SENSE
VCC
0V	RESET#

Figure 3. RESET Output vs. Supply

Figure 4. RESET Output vs. VSENSE

SUMMIT MICROELECTRONICS, Inc.

2038 2.0 6/8/00

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