Datasheet MAX44268 Datasheet (MAXIM)

EVALUATION KIT AVAILABLE

19-6144; Rev 0; 12/11

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

General Description

The MAX44268 is an ultra-small and low-power dual comparator ideal for battery-powered applications such as cell phones, notebooks, and portable medical devices that have extremely aggressive board space and power constraints. The comparator is available in a miniature

1.3mm x 1.3mm, 9-bump WLP package, making it the industry’s smallest dual comparator.

The IC can be powered from supply rails as low as 1.8V and up to 5.5V. It also features a 1.236V ±1% reference and a 0.7µA typical supply current per comparator. It has a rail-to-rail input structure and a unique output stage that limits supply current surges while switching. This design also minimizes overall power consumption under dynamic conditions. The IC has open-drain outputs, making it suitable for mixed voltage systems. The IC also features internal filtering to provide high RF immunity. It operates over a -40°C to +85°C temperature.

Applications

Smartphones Notebooks Two-Cell Battery-Powered Devices Battery-Operated Sensors Ultra-Low-Power Systems Portable Medical Mobile Accessories

Features

S Ultra-Low Power Consumption

 0.7µA per Comparator

S Ultra-Small 1.3mm x 1.3mm WLP Package

S Internal 1.236V ±1% Reference

S Guaranteed Operation Down to VCC = 1.8V

S Input Common-Mode Voltage Range Extends

200mV Beyond-the-Rails

S 6V Tolerant Inputs Independent of Supply

S Open-Drain Outputs

S Internal Filters Enhance RF Immunity

S Crowbar-Current-Free Switching

S Internal Hysteresis for Clean Switching

S No Output Phase Reversal for Overdriven Inputs

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part, refer to www.maxim-ic.com/MAX44268.related.

Typical Application Circuit

5V

V

IN

R3

INA+

REF/INA-

R2

INB+

INB-

R1

�� Maxim Integrated Products 1

MAX44268

GND

V

CC

OUTA

OUTB

POWERGOOD

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.

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

ABSOLUTE MAXIMUM RATINGS

VCC to GND ............................................................. -0.3V to +6V

INA+, REF/INA-, INB+, INB- to GND ......................-0.3V to +6V

Output Voltage to GND (OUT_) ..............................-0.3V to +6V

Output Current (OUT_) .................................................... Q50mA

Output Short-Circuit Duration (OUT_) .......................Continuous

Continuous Power Dissipation (TA = +70NC)

WLP (derate 11.9mW/NC above TA = +70NC) .............952mW

PACKAGE THERMAL CHARACTERISTICS (Note 1)

WLP

Junction-to-Ambient Thermal Resistance (qJA) ..........84°C/W

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-

layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.

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.

Continuous Input Current into Any Pin ............................ Q20mA

Operating Temperature Range .......................... -40NC to +85NC

Storage Temperature Range ............................ -65NC to +150NC

Junction Temperature .....................................................+150NC

Lead Temperature (soldering, 10s) ................................+300NC

Soldering Temperature (reflow) ......................................+260NC

ELECTRICAL CHARACTERISTICS

(VCC = 5V, V unless otherwise noted.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DC CHARACTERISTICS

Input-Referred Hysteresis V

Input Offset Voltage V

Input Bias Current I

Output-Voltage Swing Low

Input Voltage Range V

Output Short-Circuit Current

Output Leakage Current I

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

HYS

OS

B

V

OL

CM

I

SC

LEAK

= 100kI to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC,

PULLUP

(V

- 0.2V) P VCM P (VCC + 0.2V) (Note 3)

GND

V

- 0.2V P VCM P

GND

VCC + 0.2V (Note 4)

TA = +25NC

TA = -40NC to +85NC

VCC = 1.8V, I

= 1mA

SINK

VCC = 5V, I 6mA

Inferred from VOS test

Sinking, V

VCC = 5.5V, V

SINK

OUT

=

= V

OUT

TA = +25NC

-40NC P TA P +85NC

TA = +25NC

-40NC P TA P +85NC TA = +25NC

-40NC P TA P +85NC

VCC = 1.8V 3

CC

VCC = 5V 30

= 5.5V 0.2 nA

V

GND

- 0.2V

4 6 mV

0.15 5

0.15

0.2

105 200

285 350

10

300

450

V

CC

+ 0.2V

mV

nA

mV

V

mA

�� Maxim Integrated Products 2

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

ELECTRICAL CHARACTERISTICS (continued)

(VCC = 5V, V unless otherwise noted.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

AC CHARACTERISTICS

Propagation Delay High to Low (Note 5)

Propagation Delay Low to High (Note 5)

Fall Time t

POWER SUPPLY

Supply Voltage Range V

Power-Supply Rejection Ratio

Supply Current Per Comparator

Power-Up Time t

Reference Voltage V

Reference Voltage Temperature Coefficient

Reference Output Voltage Noise

Reference Line Regulation

Reference Load Regulation

Note 2: All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design. Note 3: Hysteresis is the input voltage difference between the two switching points. Note 4: VOS is the average of the positive and negative trip points minus V Note 5: Overdrive is defined as the voltage above or below the switching points.

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

Input overdrive = Q100mV, VCC = 5V

Input overdrive = Q100mV, VCC = 1.8V

t

PHL

t

PLH

F

CC

PSRR VCC = 1.8V to 5.5V 60 80 dB

I

CC

ON

REF

TC

VREF

e

N

δV

/δV

REF

δV

/δI

REF

Input overdrive = 100mV, VCC = 1.8V, Comparator A

Input overdrive = Q20mV, VCC = 5V

Input overdrive = Q20mV, VCC = 1.8V

Input overdrive = Q100mV, VCC = 5V

Input overdrive = Q100mV, VCC = 1.8V

Input overdrive = Q20mV, VCC = 5V

Input overdrive = Q20mV, VCC = 1.8V

C

LOAD

Guaranteed from PSRR tests 1.8 5.5 V

VCC = 1.8V, TA = +25NC

VCC = 5V, -40NC P TA P +85NC

TA = +25NC, 1%

-40NC < TA < +85NC

TA = +25NC, 1%

10Hz to 1kHz, C 10Hz to 6kHz, C

CCVCC

0 < I

OUT

= 100kI to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC,

PULLUP

6

7

10

14

19

38

13

39

20

= 15pF 0.2

0.6 0.95

0.7 1.15

1 ms

1.224 1.236 1.248

1.205 1.267

40

= 1nF 75

REF

= 1nF 130

REF

= 1.8V to 5.5V 0.35 mV/V

< 100nA 0.05 mV/nA

OUT

.

REF

1.4

Fs

FAVCC = 5V, TA = +25NC

V

ppm/NC

FV

RMS

�� Maxim Integrated Products 3

MAX44268

06

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Typical Operating Characteristics

(VCC = 5V, V

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

= 100kΩ to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC, unless

PULLUP

otherwise noted. All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.)

SUPPLY CURRENT vs. TRANSITION

SUPPLY CURRENT vs. SUPPLY VOLTAGE

1.8

1.6

1.4

1.2

1.0

0.8

0.6

SUPPLY CURRENT (µA)

0.4

0.2

0

1.5 6.0

V

= HIGH

OUT

TA = +85°C

TA = -40°C

TA = +25°C

SUPPLY VOLTAGE (V)

INPUT OFFSET VOLTAGE

vs. TEMPERATURE

0

-0.05

-0.10

-0.15

-0.20

-0.25

-0.30

VDD = 2.7V

-0.35

INPUT OFFSET VOLTAGE (mV)

-0.40

-0.45

-0.50

-40 100

VDD = 5V

VDD = 1.8V

TEMPERATURE (°C)

OUTPUT VOLTAGE LOW

vs. PULLUP RESISTANCE

10,000

)

EE

- V

1000

OL

100

10

OUTPUT VOLTAGE LOW (V

1

100 100k 54321

PULLUP RESISTANCE (I)

MAX44268 toc01

5.55.04.54.03.53.02.52.0

MAX44268 toc04

806020 400-20

10k1k

SUPPLY CURRENT vs. SUPPLY VOLTAGE

1.8

1.6

1.4

1.2

1.0

0.8

0.6

SUPPLY CURRENT (µA)

0.4

0.2

0

1.5 6.0

V

= LOW

OUT

TA = +85°C

TA = -40°C

TA = +25°C

SUPPLY VOLTAGE (V)

INPUT BIAS CURRENT

vs. TEMPERATURE

0.20

0.18

0.16

0.14

0.12

0.10

VDD = 2.7V

0.08

0.06

INPUT BIAS CURRENT (nA)

0.04

0.02

0

-40 100

MAX44268 toc07

VDD = 5V

VDD = 1.8V

TEMPERATURE (°C)

10

9

MAX44268 toc02

5.55.04.54.03.53.02.52.0

MAX44268 toc05

806020 400-20

8

7

6

5

4

SUPPLY CURRENT (µA)

3

2

1

0

1 10k

500

450

400

350

300

250

200

150

INPUT BIAS CURRENT (nA)

100

50

0

-1 6

SHORT-CIRCUIT CURRENT

vs. SUPPLY VOLTAGE

40

V

35

30

25

20

15

10

SHORT-CIRCUIT CURRENT (mA)

= LOW

OUT

TA = +25°C

5

0

SUPPLY VOLTAGE (V)

FREQUENCY (V

OVERDRIVE

VCC = 2.7V

VCC = 1.8V

INPUT FREQUENCY (Hz)

INPUT BIAS CURRENT

vs. COMMON-MODE VOLTAGE

VDD = 2.7V

VDD = 5V

VDD = 0V

INPUT COMMON-MODE VOLTAGE (V)

TA = -40°C

TA = +85°C

= 20mV)

VCC = 5V

1k10010

VDD = 1.8V

MAX44268 toc08

MAX44268 toc03

MAX44268 toc06

542 310

�� Maxim Integrated Products 4

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Typical Operating Characteristics (continued)

(VCC = 5V, V

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

= 100kΩ to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC, unless

PULLUP

otherwise noted. All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.)

PROPAGATION DELAY

INPUT OFFSET VOLTAGE HISTOGRAM

45

40

35

30

25

20

OCCURRENCE (%)

15

10

5

0

-2 INPUT OFFSET VOLTAGE (mV)

100

90

80

70

60

50

40

30

PROPAGATION DELAY (µs)

20

10

0

vs. INPUT OVERDRIVE (t

60

MAX44268 toc09

2.52.01.0 1.5-1.0 -0.5 0 0.5-1.5

PROPAGATION DELAY vs. CAPACITIVE LOAD

t

PLH

t

PHL

CAPACITIVE LOAD (pF)

PROPAGATION DELAY

8006004002000 1000

PLH

LEAKAGE CURRENT vs. TEMPERATURE

0.50

0.45

0.40

0.35

0.30

0.25

VCC = 5V

0.20

0.15

0.10

OUTPUT LEAKAGE CURRENT (nA)

0.05

0

-50 110

MAX44268 toc12

VCC = 2.7V

TEMPERATURE (°C)

)

MAX44268 toc10

VCC = 1.8V

907030 50-10 10-30

PROPAGATION DELAY vs. TEMPERATURE

45

40

35

30

25

20

15

PROPAGATION DELAY (µs)

10

5

0

-40 100

12

vs. PULLUP RESISTANCE

120

100

80

60

40

PROPAGATION DELAY (µs)

20

0

(V

OVERDRIVE

= 100mV, VDD = 5V)

t

PLH

t

PHL

TEMPERATURE (°C)

PROPAGATION DELAY

vs. INPUT OVERDRIVE (t

100k

PULLUP RESISTANCE (I)

806020 400-20

)

PLH

t

PLH

t

PHL

1M10k1k

MAX44268 toc13

MAX44268 toc11

10M

50

TA = -40°C

40

30

20

PROPAGATION DELAY (µs)

10

0

0 1000

INPUT OVERDRIVE VOLTAGE (mV)

TA = +25°C

TA = +85°C

MAX44268 toc14

800600400200

10

8

6

4

PROPAGATION DELAY (µs)

2

0

TA = +85°C

0 1000

INPUT OVERDRIVE VOLTAGE (mV)

TA = -40°C

TA = +25°C

800600400200

�� Maxim Integrated Products 5

MAX44268 toc15

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Typical Operating Characteristics (continued)

(VCC = 5V, V

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

= 100kΩ to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC, unless

PULLUP

otherwise noted. All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.)

INPUT-REFERRED HYSTERESIS

vs. TEMPERATURE

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

INPUT-REFERRED HYSTERESIS (mV)

0.5

0

-40 100 TEMPERATURE (°C)

SMALL-SIGNAL TRANSIENT RESPONSE

50mV/div

SMALL-SIGNAL TRANSIENT RESPONSE

= 1.8V)

(V

CC

50mV/div

MAX44268 toc16

1V/div

806020 400-20

20µs/div

MAX44268 toc17

100mV/div

LARGE-SIGNAL TRANSIENT RESPONSE

= 5V)

(V

CC

MAX44268 toc19

200mV/div

LARGE-SIGNAL TRANSIENT RESPONSE

= 1.8V)

(V

CC

1V/div

20µs/div

= 5V)

(V

CC

MAX44268 toc20

MAX44268 toc18

2V/div

200mV/div

V

2V/div

V

OUT

2V/div

20µs/div

POWER-UP RESPONSE

V

IN

CC

800µs/div

MAX44268 toc21

2V/div

-0.3V TO +6V

V

OUT

NO OUTPUT PHASE REVERSAL

V

IN

20µs/div

MAX44268 toc22

20µs/div

�� Maxim Integrated Products 6

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Typical Operating Characteristics (continued)

(VCC = 5V, V

GND

= 0V, V

IN-

= V

= 1.236V, R

IN+

= 100kΩ to VCC, TA = -40NC to +85NC. Typical values are at TA = +25NC, unless

PULLUP

otherwise noted. All devices are 100% production tested at TA = +25NC. Temperature limits are guaranteed by design.)

REF VOLTAGE vs. TEMPERATURE

1.240

1.239

1.238

1.237

1.236

1.235

1.234

REF VOLTAGE (V)

1.233

1.232

1.231

1.230

VCC = 1.8V

-60 100 TEMPERATURE (°C)

VCC = 2.7V

VCC = 5V

REF VOLTAGE vs. SUPPLY VOLTAGE

1.240

1.239

1.238

1.237

1.236

1.235

1.234

REF VOLTAGE (V)

1.233

1.232

1.231

1.230

1.5 5.5 SUPPLY VOLTAGE (V)

REF VOLTAGE vs. REF SOURCE CURRENT

AND TEMPERATURE

1.250

1.245

MAX44268 toc23

1.240

1.235

1.230

1.225

1.220

REF VOLTAGE (V)

1.215

1.210

1.205

806020 40-20 0-40

1.200 20 200

TA = +25°C

TA = +85°C

TA = -40°C

OUTPUT SOURCE CURRENT (nA)

MAX44268 toc24

180160120 14060 80 10040

REF VOLTAGE vs. REF SINK CURRENT

1.260

MAX44268 toc26

5.04.53.5 4.02.5 3.02.0

1.255

1.250

1.245

REF VOLTAGE (V)

1.240

1.235

1.230

REF VOLTAGE vs. REF SINK CURRENT

AND TEMPERATURE

1.280

1.275

1.270

1.265

1.260

1.255

1.250

REF VOLTAGE (V)

1.245

1.240

1.235

1.230 20 200

OUTPUT SINK CURRENT (nA)

VCC = 1.8V

VCC = 2.7V

VCC = 5V

OUTPUT SINK CURRENT (nA)

TA = +25°C

TA = +85°C

180160120 14060 80 1004020 200

TA = -40°C

MAX44268 toc25

180160120 14060 80 10040

MAX44268 toc27

REF VOLTAGE vs. REF SOURCE CURRENT

1.250

1.245

1.240

1.235

REF VOLTAGE (V)

1.230

1.225

1.220

VCC = 2.7V

VCC = 1.8V

VCC = 5V

OUTPUT SOURCE CURRENT (nA)

MAX44268 toc28

PERCENT OCCURRENCE (%)

180160120 14060 80 1004020 200

REF VOLTAGE DRIFT HISTOGRAM

18

16

14

12

10

8

6

4

2

0

1.230

1.232

1.234

1.231

1.233

1.235

REF VOLTAGE (V)

1.236 1.238 1.240

1.237

1.239

�� Maxim Integrated Products 7

MAX44268 toc29

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Bump Configuration

TOP VIEW

MAX44268

1

+

REF/

A

INA-

B

GND N.C.

C

INB- INB+ OUTB

23

INA+ OUTA

V

CC

WLP

PIN NAME FUNCTION

A1 REF/INA- Reference Output/Comparator A Inverting Input A2 INA+ Comparator A Noninverting Input A3 OUTA Comparator A Output B1 GND B2 N.C. No Connection

B3 V C1 INB- Comparator B Inverting Input C2 INB+ Comparator B Noninverting Input C3 OUTB Comparator B Output

CC

Negative Supply Voltage. Bypass to GND with a 1.0FF capacitor.

Positive Supply Voltage. Bypass to GND with a 1.0FF capacitor.

Bump Description

�� Maxim Integrated Products 8

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Detailed Description

The MAX44268 is a general-purpose dual comparator for battery-powered devices where area, power, and cost constraints are crucial. The IC can operate with a low

1.8V supply rail typically consuming 0.7µA quiescent current per comparator. This makes it ideal for mobile and very low-power applications. The IC’s common-mode input voltage range extends 200mV beyond-the-rails. An internal 4mV hysteresis ensures clean output switching, even with slow-moving input signals.

Input Stage Structure

The input common-mode voltage range extends from (V

- 0.2V) to (VCC + 0.2V). The comparator operates

GND

at any different input voltage within these limits with low input bias current. Input bias current is typically 0.15nA if the input voltage is between the supply rails. The device also features a 1.236V reference voltage output on the inverting input of comparator A.

The IC features a unique input ESD structure that can handle voltages from -0.3V to +6V independent of supply voltage. This allows for the device to be powered down with a signal still present on the input without damaging the part. This feature is useful in applications where one of the inputs has transient spikes that exceed the supply rails.

No Output Phase Reversal

for Overdriven Inputs

The IC’s design is optimized to prevent output phase reversal if both the inputs are within the input commonmode voltage range. If one of the inputs is outside the input common-mode voltage range, then output phase reversal does not occur as long as the other input is kept within the valid input common-mode voltage range. This behavior is shown in the No Output Phase Reversal graph in the Typical Operating Characteristics section.

Open-Drain Output

The IC features an open-drain output, enabling greater control of speed and power consumption in the circuit design. The output logic level is also independent from the input, allowing for simple level translation.

RF Immunity

The IC has very high RF immunity due to on-chip filtering of RF sensitive nodes. This allows the IC to hold its output state even in the presence of high amounts of RF noise. This improved RF immunity makes the IC ideal for mobile wireless devices.

Applications Information

Hysteresis

Many comparators oscillate in the linear region of operation because of noise or undesired parasitic feedback. This tends to occur when the voltage on one input is equal or very close to the voltage on the other input.

The hysteresis in a comparator creates two trip points: one for the rising input voltage and one for the falling input voltage (Figure 1). The difference between the trip points is the hysteresis. When the comparator’s input voltages are equal and the output trips, the hysteresis effectively causes one comparator input to move quickly past the other. This takes the input out of the region where oscillation occurs. This provides clean output transitions for noisy, slow-moving input signals. The IC has an internal hysteresis of 4mV. Additional hysteresis can be generated with three resistors using positive feedback (Figure 2).

IN+

IN-

V

HYST

OUT

Figure 1. Threshold Hysteresis Band (Not to Scale)

R2

V

IN

R4

Figure 2. Adding Hysteresis with External Resistors

THERSHOLDS

HYSTERESIS BAND

R3

V

REF

V

CC

MAX44268

GND

OUT

V

TH

V

TL

R1

�� Maxim Integrated Products 9

MAX44268

 

 

 



 



1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Use the following procedure to calculate resistor values.

1) Select R3. Input bias current at IN_+ is less than 15nA. To minimize errors caused by the input bias current, the current through R3 should be at least

1.5µA. Current through R3 at the trip point is (V V

)/R3. Considering the two possible output states

OUT

REF

-

in solving for R3 yields two formulas:

R3 = V

/IR3 and R3 = [(VCC - V

REF

)/IR3] - R1

REF

Use the smaller of the two resulting resistor values.

For example, for VCC = 5V, IR3 = -1.5µA, R1 = 200kI, and a V

= 1.236V, the two resistor values

REF

are 827kI and 1.5MI. Therefore, for R3 choose the standard value of 825kI.

2) Choose the hysteresis band required (VHB). In this example, the VHB = 50mV.

3) Calculate R2 according to the following equation:

V

= +

R2 (R1 R3 )

V

CC

HB

+

(V

REF

x R1) R 3

For this example, insert the value:

50mV

R2 (200k 0.825M ) 9.67k

= Ω+ Ω = Ω

 

5.3



For this example, choose standard value R2 = 9.76kI.

4) Choose the trip point for VIN rising (V

) in such a

THR

way that:



V

V V1

>+

THR REF

V

is the threshold voltage at which the com-

THR

parator switches its output from low to high, as V

HB



V

CC



IN

rises above the trip point. For this example, choose V

= 3V.

THR

5) Calculate R4 as follows:

=

R4



V

THR



V

REF



= = Ω

R4 6.93k

 



3 11

1.236V x 9.76 9.76 825

1

11



--



x R2 R2 R3



1

  

--

     

For this example, choose a standard value of 6.98kI.

6) Verify the trip voltages and hysteresis as follows:

111

   

= ++

VV

THR REF

= ++

VV

THF REF

xR2

   

R2 R3 R4

   

111

   

x R2

   

R2 R1 R3 R4

   

R2

-x R1 R3

+

V

CC

The hysteresis network in Figure 2 can be simplified if the reference voltage is chosen to be at midrail and the trip points of the comparator are chosen to be symmetrical about the reference voltage. Use the circuit in Figure 3 if the reference voltage can be designed to be at the center of the hysteresis band. For the symmetrical case, follow the same steps outlined in the paragraph above to calculate the resistor values except that in this case, resistor R4 approaches infinity (open). So in the previous example, using comparator B with V V

= 2.525V and V

THR

= 2.475V then using the above

THF

REF

= 2.5V, if

formulas, results in R1 = 200kI, R2 = 9.09kI, and R3 = 825kI, R4 = not installed.

Logic-Level Translator

Due to the open-drain output of the IC, the device can translate between two different logic levels (Figure 4). If the internal 4mV hysteresis is not sufficient, then external resistors can be added to increase the hysteresis as shown in Figure 2 and Figure 3.

V

CC

R3

REF

R1

is at

R2

V

IN

V

REF

Figure 3. Simplified External Hysteresis Network if V the Center of the Hysteresis Band

MAX44268

OUT

GND

�� Maxim Integrated Products 10

MAX44268

 



    

 

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Power-On-Reset Circuit

The IC can be used to make a power-on-reset circuit as displayed in Figure 5. The negative input provides the ratiometric reference with respect to the power supply and is created by a simple resistive divider. Choose reasonably large values to minimize the power consumption in the resistive divider. The positive input provides the power-on delay time set by the time constant of the RC circuit formed by R2 and C1. This simple circuit can be used to power up the system in a known state after ensuring that the power supply is stable. Diode D1 provides a rapid reset in the event of unexpected power loss. If using comparator A, R3 and R4 are not populated and REF settles in approximately 100µs.

Relaxation Oscillator

The IC can also be used to make a simple relaxation oscillator (Figure 6) using comparator B. By adding the RC circuit R5 and C1, a standard Schmidt Trigger circuit referenced to a set voltage is converted into an astable

V

CC

V

PULL

MAX44268

V

IN

V

REF

R1

OUT

multivibrator. As shown in Figure 7, IN- is a sawtooth waveform with capacitor C1 alternately charging and discharging through resistor R5. The external hysteresis network formed by R1 to R4 defines the trip voltages as:

R3 x R4

R2R3 R2R4 R3R4

++

R4R5(R1 R2 R3)

R1R 3 R 4

+

++

++ +

R2(R1R3 R3R5 R1R5)

V

T_FALL

V

T_RISE

V

=

CC

V

=

CC

R4R5 (R1 R2 R3) R1R3R4

+ ++

Using the basic time domain equations for the charging and discharging of an RC circuit, the logic-high time, logic-low time, and frequency can be calculated as:



V

t

LOW

R5C1 ln

=

T_FALL

 

V

T_RISE



Since the comparator’s output is open drain, it goes to high impedance corresponding to logic-high. So, when the output is at logic-high, the C1 capacitor charges through the resistor network formed by R1 to R5. An accurate calculation of t

would have involved

HIGH

applying thevenin’s theorem to compute the equivalent thevenin voltage (V

THEVENIN

) and thevenin resistance

GND

Figure 4. Logic-Level Translator

V

CC

R2D1

R3

R4

C1

Figure 5. Power-On Reset Circuit

�� Maxim Integrated Products 11

V

CC

MAX44268

GND

RESET

V

CC

R3

V

CC

R2

R1

Figure 6. Relaxation Oscillator

R4

C1

MAX44268

OUT

GND

R5

R1

MAX44268

 

 

 

 

11

+ 

  

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

(R

THEVENIN

) in series with the capacitor C1. t

HIGH

can then be computed using the basic time domain equations for the charging RC circuit as:

The t

V-

HIGH

V

HIGH

THEVENIN

R (R2 R4) R3 R1 R5

THEVENIN

= ++

[ ]

V (R2 R4) R3

[ ]

CC

= +



(R2 R4) R3 R1 R2 R4

x

(R2 R4) R3 R1



calculation can be simplified by selecting the

R C1 ln

=

t

THEVENIN

V-

THEVENIN



+



++ +

R1

++

V

T_RISE

V

T_FALL

V x R4

CC

component values in such a way that R3 >> R1 and R5 >> R1. This ensures that the output of the comparator goes close to VCC when at logic-high (that is, V ~ VCC and R

THEVENIN

~ R5). With this selection, t

THEVENIN

HIGH

can be approximated as:

V-

V

T_RISE

t

HIGH

R5C1 ln

=

CC

V-

V

CC

T_FALL

The frequency of the relaxation oscillator is:

Window Detector Circuit

The IC is ideal for window detectors (undervoltage/overvoltage detectors). Typical Application Circuit shows a simple window detector circuit. By changing the values of R1, R2, and R3 different voltage threshold values can be chosen. For this example, assume a single-cell Li+ battery with a 2.9V end-of-life charge, a peak charge of

4.2V, and a nominal value of 3.6V. OUTA provides an active-low undervoltage indication, and OUTB provides an active-low overvoltage indication. The open-drain outputs of both the comparators are wired ORed to give an active-high power-good signal.

The design procedure is as follows:

1) Select R1. The input bias current into INB- is less than 15nA, so the current through R1 should exceed 1.5µA for the thresholds to be accurate. In this example, choose R1 = 825kI (1.236V/1.5µA).

2) Calculate R2 + R3. The overvoltage threshold should be 4.2V when VIN is rising. The design equation is as follows:





V

+=

R2 R3 R1 x - 1

=

825 x -1

=1969k

OTH





V



REF







4.2







1.236





Ω

f

= =

tt

HIGH LOW

V

T_FALL

C1 WAVEFORM

V

T_RISE

OUT

WAVEFORM

Figure 7. Relaxation Oscillator Waveforms

R 5 C1 1n

�� Maxim Integrated Products 12

V

T_FALL

V

T_RISE

V -V

( )

CC T_RISE

V-

( )

V

T_FALL

CC

3) Calculate R2. The undervoltage threshold should be

2.9V when VIN is falling. The design equation is as follows:



V

R2 (R1 R2 R3)x - R1

=++

825 1969 x 1.236/2.9 - 825

= +

( ) ( )

( )

370k

= Ω

REF



V

UTH



For this example, choose a 374kI standard value 1%

resistor.

4) Calculate R3:

R3 (R2 R3) - R2

= +

1969k - 374k

=ΩΩ

=1.595M

Ω

For this example, choose a 1.58MI standard value 1% resistor.

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Board Layout and Bypassing

Use 1.0FF bypass capacitors from VCC to GND. To maximize performance, minimize stray inductance by putting this capacitor close to the VCC pin and reducing trace lengths. Use 1nF bypass capacitors from REF/INA- to GND as close as possible to the IC. Do not route noisy traces near REF/INA-.

Jack Detect

The IC can be used to detect peripheral devices connected to a circuit using comparator B. This includes a simple jack-detect scheme for cell phone applications. Figure 8 shows how the device can be used in conjunction with an external reference to detect an accessory ID input. The open-drain output of the devices allows the output logic level to be controlled independent of the peripheral device’s making interfacing and controlling external devices as simple as monitoring a few digital inputs on a microcontroller or codec.

load,

V

CC

V

REF

V

200kI

CONNECTOR

ACCESSORY

ID

Figure 8. Jack Detector Circuit

MAX44268

CC

GND

OUT2

V

PULL

PROCESS: BiCMOS

Chip Information

Ordering Information

PART TEMP RANGE

MAX44268EWL+T

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

-40NC to +85NC

PIN-

PACKAGE

9 WLP +AJK

TOP

MARK

�� Maxim Integrated Products 13

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Package Information

For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.

9 WLP W91B1-6

21-0430

Refer to Application Note 1891

�� Maxim Integrated Products 14

MAX44268

1.3mm x 1.3mm, Low-Power

Dual Comparator with Reference

Revision History

REVISION

NUMBER

0 12/11 Initial release —

REVISION

DATE

DESCRIPTION

PAGES

CHANGED

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 15

©

2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

Datasheet MAX44268 Datasheet (MAXIM)

Specifications and Main Features

Frequently Asked Questions

User Manual

General Description

Applications

Features

Typical Application Circuit

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

Typical Operating Characteristics

Bump Configuration

Bump Description

Detailed Description

Input Stage Structure

Open-Drain Output

RF Immunity

Hysteresis

Logic-Level Translator

Power-On-Reset Circuit

Relaxation Oscillator

Figure 4. Logic-Level Translator

Figure 5. Power-On Reset Circuit

Figure 6. Relaxation Oscillator

Window Detector Circuit

Board Layout and Bypassing

Jack Detect

Figure 8. Jack Detector Circuit

Chip Information

Ordering Information

Package Information

Revision History