Datasheet

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LTC2935

2935fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Ultra-Low Power Supervisor

with Power-Fail Output,

Selectable Thresholds

The LTC

2935 ultra-low power voltage monitor provides

system initialization, power-fail warning and reset gen-

eration functions. Low quiescent current (500nA typical)

makes the LTC2935 an ideal choice for battery-operated

applications.

Three binary threshold-select inputs conﬁ gure one of

eight integrated reset thresholds, ranging from 1.6V to

3.45V in pre-determined increments. Early warning of an

impending low voltage condition is provided at the power-

fail output (PFO), whose threshold is above the conﬁ gured

reset threshold. Supervisory circuits monitor V

and

pull RST low when V

drops below the conﬁ gured reset

threshold. When V

is rising from an under-threshold

condition, an internal reset timer is started after exceeding

the reset threshold by 5%. A 200ms reset timeout delays

the return of the RST output to a high state. A pushbut-

ton switch connected to the MR input is typically used to

force a manual reset. Outputs RST and PFO are available

with open-drain (LTC2935-1/LTC2935-3) or active pull-up

(LTC2935-2/LTC2935-4) circuits. Operating temperature

range is from –40°C to 85°C.

Conﬁ gurable Low Power Voltage Monitor

500nA Quiescent Current

±1.5% (Max) Accuracy over Temperature

Integrated Precision Attenuators

Eight Pin-Selectable Reset Thresholds

Eight Pin-Selectable Power-Fail Thresholds

Early Warning Power-Fail Output

200ms Reset Timeout

Manual Reset Input

Compact 8-Lead, 2mm × 2mm DFN and

TSOT-23 (ThinSOT™) Packages

Portable Equipment

Battery-Powered Equipment

Security Systems

Point-of-Sale Devices

Wireless Systems

Falling Threshold Selection Table

BATTERY

POWERED

SYSTEM

LOGIC

2935 TA01a

0.1μF

PFO

RST

LTC2935-2

GND

LTC2935-1/LTC2935-2 LTC2935-3/LTC2935-4

RESET

THRESHOLD

(V)

POWER-FAIL

THRESHOLD

(V)

RESET

THRESHOLD

(V)

POWER-FAIL

THRESHOLD

(V) S2S1S0

3.30 3.45 2.44 2.56 Low Low Low

3.15 3.30 2.32 2.44 Low Low High

3.00 3.15 2.20 2.32 Low High High

2.85 3.00 2.08 2.20 Low High Low

2.70 2.85 1.96 2.08 High High Low

2.55 2.70 1.84 1.96 High Low Low

2.40 2.55 1.72 1.84 High Low High

2.25 2.40 1.60 1.72 High High High

L, LT, LTC, LTM, Linear Technology and the Linear logo 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.

Summary of content (12 pages)

PAGE 1
LTC2935 Ultra-Low Power Supervisor with Power-Fail Output, Selectable Thresholds FEATURES DESCRIPTION n The LTC®2935 ultra-low power voltage monitor provides system initialization, power-fail warning and reset generation functions. Low quiescent current (500nA typical) makes the LTC2935 an ideal choice for battery-operated applications. n n n n n n n n 500nA Quiescent Current ±1.
PAGE 2
LTC2935 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) Input Voltages VCC........................................................... –0.3V to 6V S2, S1, S0, MR .........................–0.3V to (VCC + 0.3V) Output Voltages (PFO, RST) LTC2935-1/LTC2935-3 ............................. –0.3V to 6V LTC2935-2/LTC2935-4 ..............–0.3V to (VCC + 0.3V) RMS Currents PFO, RST ..........................................................±5mA Operating Ambient Temperature Range LTC2935C .....................................
PAGE 3
LTC2935 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C, VCC = 3.6V, unless otherwise noted. (Note 2) SYMBOL PARAMETER VCC VCC Input Supply Voltage CONDITIONS l MIN ICC VCC Input Supply Current l 225 S2 = Low : S1 = Low : S0 = Low l TYP MAX UNITS 5.5 V 500 1000 nA 3.251 3.300 3.
PAGE 4
LTC2935 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C, VCC = 3.6V, unless otherwise noted.
PAGE 5
LTC2935 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs S0, S1, S2 Input Voltage Supply Current vs MR Input Voltage 5 VCC = 3.6V 200 4 150 3 ICC (μA) ICC (μA) 250 TA = 25°C, unless otherwise noted. 100 50 VCC = 3.6V 2 1 0 0 0 0.5 1 1.5 2 2.5 3 S0, S1, S2 INPUT VOLTAGE (V) 3.5 4 2935 G07 0 0.5 1 1.5 2 2.5 3 MR INPUT VOLTAGE (V) 3.5 4 2935 G08 PIN FUNCTIONS Exposed Pad (DFN Only): Exposed Pad may be left ﬂoating or connected to device ground. GND: Device ground.
PAGE 6
LTC2935 BLOCK DIAGRAM LTC2935-2/LTC2935-4 MR VCC 900k VCC – RST RC RESET DELAY + S0 LTC2935-2/LTC2935-4 S1 VCC S2 0.
PAGE 7
LTC2935 APPLICATIONS INFORMATION VOLTAGE MONITORING Unmanaged power can cause various system problems. At power-up, voltage ﬂuctuation around critical thresholds can cause improper system or processor initialization. The LTC2935 provides power management capabilities for the system power-up phase. The supervisory device issues a system reset after the monitored voltage has stabilized.
PAGE 8
LTC2935 APPLICATIONS INFORMATION Selecting Output Logic Style The LTC2935 status outputs are available in two options: open-drain (LTC2935-1/LTC2935-3) or active pull-up (LTC2935-2/LTC2935-4). The open-drain options (LTC2935-1/LTC2935-3) allow the outputs to be pulled up to a user deﬁned voltage with a resistor. The open-drain pull-up voltage may be greater than VCC (5.5V maximum), which is not always possible with inferior battery supervisors, due to internal clamps.
PAGE 9
LTC2935 TYPICAL APPLICATIONS Battery Monitor with Interface to Low Voltage Logic 3μA LDO IN SHDN LT3009 OUT GND ADJ 1.8V 1.18M 1μF 590k 100k 100k VCC + Li-Ion 0.1μF S1 S2 RESD* 10k VDD PFO S0 NMI LTC2935-1 μP RST MR RST GND MANUAL PB1 RESET PUSHBUTTON POWER FAIL FALLING THRESHOLD = 3.15V RESET FALLING THRESHOLD = 3.00V 2935 TA02 *OPTIONAL RESISTOR FOR ADDED ESD PROTECTION Alkaline Cell Stack Voltage Monitor VCC + 1.5V 0.
PAGE 10
LTC2935 PACKAGE DESCRIPTION DC Package 8-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1719 Rev Ø) 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 0.64 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.45 BSC 1.37 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED R = 0.05 TYP 2.00 ±0.10 (4 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) R = 0.115 TYP 5 8 0.40 ± 0.10 0.64 ± 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER (DC8) DFN 0106 REVØ 4 0.
PAGE 11
LTC2935 PACKAGE DESCRIPTION TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 2.90 BSC (NOTE 4) 0.65 REF 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) 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 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.95 BSC TS8 TSOT-23 0802 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 12
LTC2935 TYPICAL APPLICATION Portable Device Battery Monitor 3μA LDO 1.8V IN + VCC Li-Ion 0.1μF MR 100k LT3009 OUT GND ADJ SHDN 1.18M S0 S1 S2 LTC2935-1 GND 1μF RST 590k 100k LOW BATTERY EARLY WARNING PFO POWER FAIL FALLING THRESHOLD = 3.15V RESET FALLING THRESHOLD = 3.00V 2935 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC690 5V Supply Monitor, Watchdog Timer and Battery Backup 4.65V Threshold LTC694-3.3 3.3V Supply Monitor, Watchdog Timer and Battery Backup 2.