View MAX6457_108304.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-2534; Rev 1; 6/03
High-Voltage, Low-Current Voltage Monitors in SOT Packages
General Description
The MAX6457-MAX6460 high supply voltage, low-power voltage monitors operate over a 4V to 28V supply voltage range. Each device includes a precision bandgap reference, one or two low-offset voltage comparators, internal threshold hysteresis, power good or reset timeout options, and one or two high-voltage open-drain outputs. Two external resistors (three for window detection) set the trip threshold voltages. The MAX6457 is a single voltage monitor for undervoltage or overvoltage detection. A logic-based clear input either latches the output for overvoltage applications or allows the device to operate in transparent mode. The MAX6458 includes two comparators (one overvoltage and one undervoltage) for window detection and a single output to indicate if the monitored input is within an adjustable voltage window. The MAX6459 includes dual overvoltage/ undervoltage comparators with two independent comparator outputs. Use the MAX6459 as a window comparator with separate undervoltage and overvoltage outputs or as two independent, single voltage monitors. The MAX6460 includes a single comparator and an internal reference, and can also accept an external reference. The inverting and noninverting inputs of the comparator are externally accessible to support positive or negative voltage monitors and to configure the device for activehigh or active-low output logic. The MAX6457/MAX6458 offer fixed timing options as a voltage detector with a 50s typical delay or as a reset circuit with a 90ms minimum reset timeout delay. The monitored input must be above the adjusted trip threshold (or within the adjusted voltage window for the MAX6458) for the selected timeout period before the output changes state. The MAX6459/MAX6460 offer only a fixed 50s timeout period. Internal threshold hysteresis options (0.5%, 5%, and 8.3% for the MAX6457/MAX6458/MAX6459, and 0.5% for the MAX6460) reduce output chatter in noisesensitive applications. Each device is available in a small SOT23 package and specified over the extended temperature range of -40C to +125C. o Internal 2.25V 2.5% Reference o Low Current (3.5A, typ at 12V) o Open-Drain N-Channel Output (28V Compliant) o Internal Threshold Hysteresis Options (0.5%, 5%, 8.3%) o Two IN-to-OUT Timeout Period Options (50s, 150ms) o Internal Undervoltage Lockout o Immune to Short Voltage Transients o Small SOT23 Packages o Few External Components o Fully Specified from -40C to +125C
Features
o Wide Supply Voltage Range, 4V to 28V
MAX6457-MAX6460
Ordering Information
PART MAX6457UKD_ _-T MAX6458UKD_ _-T MAX6459UT_-T TEMP RANGE -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 5 SOT23-5 5 SOT23-5 6 SOT23-6
MAX6460UT-T -40C to +125C 6 SOT23-6 Note: The MAX6457/MAX6458/MAX6459 are available with factory-trimmed internal hysteresis options. The MAX6457 and MAX6458 offer two fixed timing options. Select the desired hysteresis and timing options using Table 1 or the Selector Guide at the end of the data sheet, and enter the corresponding letters and numbers in the part number by replacing "_ _" or "_". These devices are offered in tape-and-reel only and must be ordered in 2500-piece increments.
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
BATTERY CHARGER +21V (NOMINAL) IN OUT DC-DC CONVERTER SHDN VCC
Applications
Undervoltage Monitoring/Shutdown Overvoltage Monitoring/Protection Window Voltage Detection Circuitry Multicell Battery-Stack Powered Equipment Notebooks, eBooks Automotive Industrial Telecom Networking
R1 5-CELL Li+ BATTERY STACK IN+ R2 GND
MAX6457
OUT
RPULLUP
LOAD
CLEAR
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
ABSOLUTE MAXIMUM RATINGS
VCC, OUT, OUTA, OUTB, CLEAR to GND ..........-0.3V to +30.0V IN+, IN- to GND..........................................-0.3V to (VCC + 0.3V) REF to GND..............-0.3V to the lower of +6V and (VCC + 0.3V) Input Currents (VCC, IN+, IN-) ............................................20mA Sink Current (OUT, OUTA, OUTB) ......................................20mA Continuous Power Dissipation (TA = +70C) 5-Pin SOT23 (derate 7.1 mW/C above +70C)............571mW 6-Pin SOT23 (derate 8.7 mW/C above +70C)............696mW Junction Temperature ......................................................+150C Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VCC = 4V to 28V, TA = -40C to +125C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range Supply Current SYMBOL VCC ICC (Note 2) VCC = 5V, no load VCC = 12V, no load VCC = 24V, no load VTH+ TA = -40C to +85C, VCC 4V VIN rising TA = +85C to +125C, VCC 4V MAX645_U_D_A Threshold Voltage VTHTA = -40C to +85C TA = +85C to +125C 1.195 1.170 1.180 1.155 1.133 1.111 1.093 1.071 0.5 5 8.3 0 -55 50 VCC +55 V nA s %VTH+ CONDITIONS MIN 4 2 3.5 6.5 1.228 TYP MAX 28 5 7.5 12.5 1.255 1.255 1.255 1.255 1.194 1.194 1.151 1.151 V A UNITS V
TA = -40C to +85C VIN MAX645_U_D_B falling TA = +85C to +125C MAX645_U_D_C MAX64_ _U_D_A TA = -40C to +85C TA = +85C to +125C
Threshold Voltage Hysteresis IN Operating Voltage Range IN Leakage Current VIN IIN
MAX64_ _U_D_B MAX64_ _U_D_C (Note 2) VIN = 1.25V, VCC = +28V MAX645_UKD0_ MAX6459UT_ MAX6460UT MAX6457 and MAX6458 only, D3 option 90
OUT Timeout Period
tTP
150 2
210
ms ms
Startup Time CLEAR Input Logic Voltage (MAX6457) VIL VIH
VCC rising from GND to VCC 4V in less than 1s (Note 3) 2
0.4
V
2
_______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 4V to 28V, TA = -40C to +125C, unless otherwise specified. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS VCC 1.5V, ISINK = 250A, OUT asserted, TA = -40C to +85C VCC 4.0V, ISINK = 1mA, OUT asserted, TA = -40C to +125C VCC = 5V, VOUT = 28V (Note 4) OUT asserted, OUT = VCC REF = GND VREF TA = -40C to +85C TA = +85C to +125C Sourcing: 0 IREF 100A, sinking: 0 |IREF| 300nA VOFFSET IBIAS IOFFSET CMVR CMRR PSRR VIN+ = VIN- = 1.4V 0 80 80 VIN+ = 1.4V, VIN- = 1V -4.5 6 -25 2 1.4 +25 2.183 2.171 10 7 2.25 2.25 50 +4.5 2.303 2.303 MIN TYP MAX 0.4 V 0.4 500 nA mA mA V V/A mV mV nA pA V dB dB UNITS
MAX6457-MAX6460
Output Voltage Low
VOL
Output Leakage Current Output Short-Circuit Sink MAX6460 Reference Short-Circuit Current Reference Output Voltage Load Regulation Input Offset Voltage Input Hysteresis Input Bias Current Input Offset Current Common-Mode Voltage Range Common-Mode Rejection Ratio Comparator Power-Supply Rejection Ratio
ILKG ISC
Note 1: Devices are production tested at +25C. Overtemperature limits are guaranteed by design. Note 2: IN voltage monitoring requires that VCC 4V, but OUT remains asserted in the correct undervoltage lockout state for VCC down to 1.5V. Note 3: Startup time is the time required for the internal regulator and reference to reach specified accuracy after the monitor is powered up from GND. Note 4: The open-drain output can be pulled up to a voltage greater than VCC but cannot exceed +28V.
_______________________________________________________________________________________
3
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
Typical Operating Characteristics
(GND = 0, RPULLUP = 10k, and TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6457-60 toc01
TRIP THRESHOLD VOLTAGE vs. TEMPERATURE (0.5% HYSTERESIS)
MAX6457-60 toc02
TRIP THRESHOLD VOLTAGE vs. TEMPERATURE (5% HYSTERESIS)
MAX6457-60 toc03
12 10 8 ICC (A) 6 4 TA = -40C 2 0 4 10 16 VCC (V) 22 TA = +125C TA = +25C
1.25 VTH+ (RISING) TRIP THRESHOLD VOLTAGE (V) 1.23 1.21 1.19 1.17 1.15 1.13 1.11 VTH- (FALLING)
1.25 TRIP THRESHOLD VOLTAGE (V) 1.23 1.21 1.19 1.17 1.15 1.13 1.11 VTH- (FALLING) VTH+ (RISING)
28
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
TRIP THRESHOLD VOLTAGE vs. TEMPERATURE (8.3% HYSTERESIS)
MAX6457-60 toc04
OUTPUT LOW VOLTAGE vs. OUTPUT SINK CURRENT
MAX6457-60 toc05
1.25 TRIP THRESHOLD VOLTAGE (V) 1.23 1.21 1.19 1.17 1.15 1.13 1.11 VTH- (FALLING) VTH+ (RISING)
100,000 10,000 TA = +125C 1000 VOL (mV) 100 10 1 VCC = 12V 0.1 TA = +25C TA = -40C
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0.01
0.1
1 ISINK (mA)
10
100
4
_______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages
Typical Operating Characteristics (continued)
(GND = 0, RPULLUP = 10k, and TA = +25C, unless otherwise noted.)
MAX6457-MAX6460
OUTPUT SHORT-CIRCUIT SINK CURRENT vs. TEMPERATURE
MAX6457-60 toc06
TIMEOUT PERIOD vs. TEMPERATURE
MAX6457-60 toc07
OUTPUT FALL TIME vs. SUPPLY VOLTAGE
1800 1600 OUTPUT FALL TIME (ns) 1400 1200 1000 800 600 400 200 TA = -40C 4 8 12 16 VCC (V) 20 24 28 TA = +25C
MAX6457-60 toc08
15 14 13 ISC (mA) VCC = 12V
1000
2000 TA = +125C
100 MAX6457UKD3
VCC = 5V 11 10 9 8 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VCC = 24V
tTP (ms)
12
10
1 MAX6457UKD0 0.1
0.01 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0
MAXIMUM TRANSIENT DURATION vs. INPUT OVERDRIVE
MAX6457-60 toc09
INPUT LEAKAGE CURRENT vs. TEMPERATURE
VIN = 1.25V 8 6 IIN (nA) 4 2 0 -2
MAX6457-60 toc10
300 MAXIMUM TRANSIENT DURATION (s) 250 200 150 100 50 0 1 10 100 OUT ASSERTED LOW ABOVE THIS LINE
10
1000
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
INPUT OVERDRIVE (VTH- - VIN+) (mV)
_______________________________________________________________________________________
5
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
Pin Description
PIN MAX6457 MAX6458 MAX6459 MAX6460 NAME FUNCTION MAX6457: Open-Drain Monitor Output. OUT requires an external pullup resistor. OUT asserts low for VCC between 1.5V and 4V. OUT asserts low when VIN+ drops below VTH- and goes high after the timeout period (tTP) when VIN+ exceeds VTH+. MAX6458: Open-Drain Monitor Output. OUT requires an external pullup resistor. OUT asserts low for VCC between 1.5V and 4V. OUT asserts low when VIN+ drops below VTH- or when VIN- exceeds VTH+. OUT goes high after the timeout period (tTP) when VIN+ exceeds VTH+ and VINdrops below VTH-. MAX6460: Open-Drain Monitor Output. OUT requires an external pullup resistor. OUT asserts low for VCC between 1.5V and 4V. OUT asserts low when VIN+ drops below VIN-. OUT goes high when VIN+ is above VIN-. Open-Drain Monitor A Undervoltage Output. OUTA requires an external pullup resistor. OUTA goes low when VIN+ drops below VTH- and goes high when VIN+ exceeds VTH+. OUTA also goes low when VCC drops below 4V. Open-Drain Monitor B Overvoltage Output. OUTB requires an external pullup resistor. OUTB goes low when VIN- exceeds VTH+ and goes high when VIN- drops below VTH-. OUTB also goes low when VCC drops below 4V. Ground Adjustable Undervoltage Monitor Threshold Input. Noninverting input for MAX6460. Adjustable Overvoltage Monitor Threshold Input. Inverting input for MAX6460. Clear Input. For VIN+ > VTH+, drive CLEAR high to latch OUT high. Connect CLEAR to GND to make the latch transparent. CLEAR must be low when powering up the device. Connect CLEAR to GND when not used. Reference. Internal 2.25V reference output. Connect REF to IN+ through a voltage divider for active-low output. Connect REF to IN- through a voltage divider for active-high output. REF can source up to 100A and sink up to 300nA. Leave REF floating when not used. REF output is stable with capacitive loads from 0 to 50pF or greater than 1F. Supply Voltage
1
1
--
1
OUT
--
--
1
--
OUTA
--
--
5
--
OUTB
2 3 --
2 3 4
2 3 4
2 3 4
GND IN+ IN-
4
--
--
--
CLEAR
--
--
--
5
REF
5
5
6
6
VCC
6
_______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages
Functional Diagrams
VCC VCC IN+
MAX6457-MAX6460
MAX6457
IN+ TIMEOUT OPTION HYSTERESIS OPTION LATCH OUT IN-
UV
MAX6458
TIMEOUT OPTION
OUT
OV HYSTERESIS OPTION CLEAR 1.228V GND GND "UV": UNDERVOLTAGE "OV": OVERVOLTAGE
1.228V
Figure 1. MAX6457 Functional Diagram
Figure 2. MAX6458 Functional Diagram
VCC VCC
IN+ UV
MAX6459
OUTA IN+ OUT
INOV HYSTERESIS OPTION OUTB
INREF
MAX6460
2.25V "UV": UNDERVOLTAGE "OV": OVERVOLTAGE GND GND
1.228V
Figure 3. MAX6459 Functional Diagram
Figure 4. MAX6460 Functional Diagram
_______________________________________________________________________________________
7
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
Detailed Description
Each of the MAX6457-MAX6460 high-voltage (4V to 28V), low-power voltage monitors include a precision bandgap reference, one or two low-offset-voltage comparators, internal threshold hysteresis, internal timeout period, and one or two high-voltage open-drain outputs. R4 VREFD = VREF R 3 + R4 V R1= R2 TRIP - 1 VREFD where VREF = reference output voltage (2.25V, typ), VREFD = divided reference, VTRIP = desired trip threshold in (in volts). For an active-low power-good output, connect the resistor divider R1 and R2 to the inverting input and the reference-divider network to the noninverting input. Alternatively, connect an external reference less than 1.4V to either input.
Programming the Trip Voltage (VTRIP) Two external resistors set the trip voltage, VTRIP (Figure 5). VTRIP is the point at which the applied voltage (typically VCC) toggles OUT. The MAX6457/MAX6458/MAX6459/ MAX6460's high input impedance allows large-value resistors without compromising trip-voltage accuracy. To minimize current consumption, select a value for R2 between 10k and 1M, then calculate R1 as follows:
V R1 = R2 TRIP - 1 VTH
VCC
VTRIP
RPULLUP VCC R1 IN+ R2 GND R1 + R2 R2
R1 VCC IN+
RPULLUP
MAX6457- MAX6460
OUT (OUTB FOR MAX6459)
REF OUT (OUTB) R2 VREFD R4 INGND R3
MAX6460
OUT
OUT
VTRIP = VTH
Figure 5a. Programming the Trip Voltage
Figure 5b. Programming the MAX6460 Trip Voltage
VHYST VTH+ VIN+ VTH-
where VTRIP = desired trip voltage (in volts), VTH = threshold trip voltage (VTH+ for overvoltage detection or VTH- for undervoltage detection). Use the MAX6460 voltage reference (REF) to set the trip threshold by connecting IN+ or IN- through a voltage divider (within the inputs common-mode voltage range) to REF. Small leakage currents into the comparators inputs allows use of large value resistors to prevent loading the reference and affecting its accuracy. Figure 5b shows an active-high power-good output. Use the following equation to determine the resistor values when connecting REF to IN-:
8
VCC VOUT 0 tTP tTP
Figure 6. Input and Output Waveforms (Noninverting Input Varied)
_______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
>VTH+ IN+ VCC CLEAR 0
VCC OUT 0 tTP tTP tTP
Figure 7. Timing Diagram (MAX6457)
Hysteresis
Hysteresis adds noise immunity to the voltage monitors and prevents oscillation due to repeated triggering when VIN is near the threshold trip voltage. The hysteresis in a comparator creates two trip points: one for the rising input voltage (VTH+) and one for the falling input voltage (VTH-). These thresholds are shown in Figure 6. The internal hysteresis options of the MAX6457/ MAX6458/MAX6459 are designed to eliminate the need for adding an external hysteresis circuit.
BATTERY CHARGER +21V IN OUT DC-DC CONVERTER SHDN VCC
R1 5-CELL Li+ BATTERY STACK IN+ R2 GND
MAX6457- MAX6460
OUT (OUTA FOR MAX6459)
RPULLUP
LOAD
Timeout Period
The timeout period (tTP) for the MAX6457 is the time from when the input (IN+) crosses the rising input threshold (VTH+) to when the output goes high (see Figures 6 and 7). For the MAX6458, the monitored voltage must be in the "window" before the timeout starts. The MAX6459 and MAX6460 do not offer the extended timeout option (150ms). The extended timeout period is suitable for overvoltage protection applications requiring transient immunity to avoid false output assertion due to noise spikes.
Figure 8. Undervoltage Lockout Typical Application Circuit
Latched-Output Operation
The MAX6457 features a digital latch input (CLEAR) to latch any overvoltage event. If the voltage on IN+ (VIN+) is below the internal threshold (VTH-), or if VCC is below
4V, OUT remains low regardless of the state of CLEAR. Drive CLEAR high to latch OUT high when VIN+ exceeds VTH+. When CLEAR is high, OUT does not deassert if VIN+ drops back below VIN-. Toggle CLEAR to deassert OUT. Drive CLEAR low to make the latch transparent (Figure 7). CLEAR must be low when powering up the MAX6457. To initiate self-clear at power-up, add a 100k pullup resistor from CLEAR to VCC and a 1F capacitor from CLEAR to GND to hold CLEAR low. Connect CLEAR to GND when not used. See Figure 9.
_______________________________________________________________________________________
9
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
VSUPPLY R1 IN+ 100k R2 CLEAR VCC FUSE VSUPPLY VCC
LOAD
MAX6457- MAX6460
OUT (OUTB FOR MAX6459)
RPULLUP
LOAD
R1 IN+ R2
MAX6457- MAX6460
OUT (OUTB FOR MAX6459) GND
R3 SCR
1F
GND
Figure 9. Overvoltage Shutdown Circuit (with External Pass MOSFET)
Figure 10. Overvoltage Shutdown Circuit (with SCR Fuse)
Applications Information
Undervoltage Lockout
Figure 8 shows the typical application circuit for detecting an undervoltage event of a 5-cell Li+ battery stack. Connect OUT of the MAX6457/MAX6458/MAX6460 (OUTA of the MAX6459) to the shutdown input of the DCDC converter to cut off power to the load in case of an undervoltage event. Select R1 and R2 to set the trip voltage (see the Programming the Trip Voltage section). When the voltage of the battery stack decreases so that VIN+ drops below VTH- of the MAX6457-MAX6460, then OUT (OUTA) goes low and disables the power supply to the load. When the battery charger restores the voltage of the 5-cell stack so that VIN+ > VTH+, OUT (OUTA) goes high and the power supply resumes driving the load.
Window Detection
The MAX6458/MAX6459 include undervoltage and overvoltage comparators for window detection (Figures 2 and 3). The circuit in Figure 11 shows the typical configuration for this application. For the MAX6458, OUT asserts high when VCC is within the selected "window." When VCC falls below the lower limit of the window (VTRIPLOW) or exceeds the upper limit (VTRIPHIGH), OUT asserts low. The MAX6459 features two independent open-drain outputs: OUTA (for undervoltage events) and OUTB (for overvoltage events). When VCC is within the selected window, OUTA and OUTB assert high. When VCC falls below V TRIPLOW , OUTA asserts low while OUTB
VCC
Overvoltage Shutdown
The MAX6457-MAX6460 are ideal for overvoltage shutdown applications. Figure 9 shows a typical circuit for this application using a pass P-channel MOSFET. The MAX6457-MAX6460 are powered directly from the system voltage supply. Select R1 and R2 to set the trip voltage (see the Programming the Trip Voltage section). When the supply voltage remains below the selected threshold, a low logic level on OUT (OUTB for MAX6459) turns on the P-channel MOSFET. In the case of an overvoltage event, OUT (OUTB) asserts high, turns off the MOSFET, and shuts down the power to the load. Figure 10 shows a similar application using a fuse and a silicon-controlled rectifier (SCR). An overvoltage event turns on the SCR and shorts the supply to ground. The surge of current through the short circuit blows the fuse and terminates the current to the load. Select R3 so that the gate of the SCR is properly biased when OUT (OUTB) goes high impedance.
10
VCC VCC RPULLUP OUT MAX6458 ONLY IN+ R2 INR3 OUTA OUTB MAX6459 ONLY GND OUT
R1
VCC
MAX6458 MAX6459
RPULLUP RPULLUP OUTA OUTB
Figure 11. Window Detection
______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages
remains high. When VCC exceeds VTRIPHIGH, OUTB asserts low while OUTA remains high. VTRIPLOW and VTRIPHIGH are given by the following equations: R VTRIPLOW = VTH- TOTAL R2 + R3 VTRIPHIGH R = VTH+ TOTAL R3
Example Calculations for Window Detection
The following is an example for calculating R1, R2, and R3 of Figure 11 for window detection. Select the upper and lower trip points (VTRIPHIGH and VTRIPLOW). VCC = 21V VTRIPHIGH = 23.1V VTRIPLOW = 18.9V For 5% hysteresis, VTH+ = 1.228 and VTH- = 1.167. 1) Choose RTOTAL = 4.2M = R1 + R2 + R3 2) Calculate R3 R3 = VTH+ x RTOTAL (1.228V) (4.2M) = VTRIPHIGH 23.1V
MAX6457-MAX6460
where RTOTAL = R1 + R2 + R3. Use the following steps to determine the values for R1, R2, and R3. 1) Choose a value for RTOTAL, the sum of R1, R2, and R3. Because the MAX6458/MAX6459 have very high input impedance, RTOTAL can be up to 5M. 2) Calculate R3 based on R TOTAL and the desired upper trip point: V x RTOTAL R3 = TH+ VTRIPHIGH 3) Calculate R2 based on RTOTAL, R3, and the desired lower trip point: V x RTOTAL R2 = TH- R3 VTRIPLOW 4) Calculate R1 based on RTOTAL, R3, and R2: R1 = RTOTAL - R2 - R3
= 223.273k 3) Calculate R2
VCC (4V TO 28V) VCC RPULLUP VOUT (UP TO 28V)
MAX6457- MAX6460
OUT/ OUTA/ OUTB
OUT/ OUTA/ OUTB
GND
Figure 13. Interfacing to Voltages Other than VCC
VCC VMON VCC RPULLUP R1 IN+ R2
VCC
VCC INRPULLUP
MAX6457- MAX6460
OUT (OUTB FOR MAX6459)
MAX6460
OUT (OUTB)
R1 IN+ GND OUT REF OUT
GND
R2
VNEG
Figure 12. Monitoring Voltages Other than VCC
Figure 14. Monitoring Negative Voltages 11
______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
Table 1. Factory-Trimmed Internal Hysteresis and Timeout Period Options
PART SUFFIX 0A 0B MAX6457UKD_ _ -T MAX6458UKD_ _ -T 0C 3A 3B 3C A MAX6459UT_ -T MAX6460UT-T B C N/A TIMEOUT OPTION 50s 50s 50s 150ms 150ms 150ms 50s 50s 50s 50s HYSTERESIS OPTION (%) 0.5 5 8.3 0.5 5 8.3 0.5 5 8.3 0.5
Selector Guide
PART MAX6457UKD0A-T MAX6457UKD3A-T MAX6457UKD0B-T MAX6457UKD3B-T MAX6457UKD0C-T MAX6457UKD3C-T MAX6458UKD0A-T MAX6458UKD3A-T MAX6458UKD0B-T MAX6458UKD3B-T MAX6458UKD0C-T MAX6458UKD3C-T MAX6459UTA-T MAX6459UTB-T MAX6459UTC-T MAX6460UT-T PIN COUNT 5 5 5 5 5 5 5 5 5 5 5 5 6 6 6 6 LATCHED OUTPUT -- -- -- -- -- -- -- -- -- -- NUMBER OF OUTPUTS 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 1 HYSTERESIS (%VTH+) 0.5 0.5 5 5 8.3 8.3 0.5 0.5 5 5 8.3 8.3 0.5 5 8.3 0.5 TIMEOUT PERIOD 50s 150ms 50s 150ms 50s 150ms 50s 150ms 50s 150ms 50s 150ms 50s 50s 50s 50s TOP MARK AEAA AANN AANL AANO AANM ADZZ AANP AANS AANQ AEAB AANR AANT ABML ABEJ ABMM ABEG COMPARATORS 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 1
12
______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
R2 = = VTH- x RTOTAL - R3 VTRIPLOW
Interfacing to Voltages Other than VCC
The open-drain outputs of the MAX6457-MAX6460 allow the output voltage to be selected independent of VCC. For systems requiring an output voltage other than VCC, connect the pullup resistor between OUT, OUTA, or OUTB and any desired voltage up to 28V (see Figure 13).
(1.167V) (4.2M) - 223.273k 18.9V = 36.06k
Monitoring Negative Voltages
Figure 14 shows the typical application circuit for monitoring negative voltages (VNEG) using the MAX6460. Select a value for R1 between 25k and 1M. Use the following equation to select R2: R2 = R1 x -VNEG VREF
4) Calculate R1 R1 = RTOTAL - R2 - R3 = 4.2M - 223.273k - 36.06k = 3.94067M
Monitoring Voltages Other than VCC
The MAX6457-MAX6460 can monitor voltages other than V CC (Figure 12). Calculate V TRIP as shown in the Programming the Trip Voltage section. The monitored voltage (VMON) is independent of VCC. VIN+ must be within the specified operating range: 0 to VCC.
where VREF = 2.25V and VNEG < 0. VIN+ must always be within the specified operating range: 0 to VCC.
Pin Configurations
TOP VIEW
OUT 1 5 VCC OUT 1 5 VCC
GND 2
MAX6457
GND 2
MAX6458
IN+ 3
4
CLEAR
IN+ 3
4
IN-
SOT23
SOT23
OUTA 1
6
VCC
OUT 1
6
VCC
GND 2
MAX6459
5
OUTB
GND 2
MAX6460
5
REF
IN+ 3
4
IN-
IN+ 3
4
IN-
SOT23
SOT23
Chip Information
TRANSISTOR COUNT: 785 PROCESS: BiCMOS
______________________________________________________________________________________ 13
High-Voltage, Low-Current Voltage Monitors in SOT Packages MAX6457-MAX6460
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOT-23 5L .EPS
PACKAGE OUTLINE, SOT-23, 5L
21-0057
E
1 1
14
______________________________________________________________________________________
High-Voltage, Low-Current Voltage Monitors in SOT Packages
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
6LSOT.EPS
MAX6457-MAX6460
PACKAGE OUTLINE, SOT-23, 6L
21-0058
F
1 1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX6457

	To Download MAX6457 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .