Low-Cost, Micropower, High-Side Current-Sense Amplifier + Comparator + Reference ICs

Transcription

1 9-63; Rev ; /3 Low-Cost, Micropower, High-Side Current-Sense General Description The low-cost, micropower, high-side current-sense supervisors contain a highside current-sense amplifier, bandgap reference, and comparator with latching output. They feature a voltage output that eliminates the need for gain-setting resistors, making them ideal for today s notebook computers, cell phones, and other systems where battery/dc current monitoring is critical. High-side current monitoring is especially useful in battery-powered systems since it does not interfere with the ground path of the battery charger. The to +8 input common-mode range is independent of the supply voltage, which ensures that the current-sense feedback remains viable even when connected to a battery pack in deep discharge. The comparator output of the MAX4373/MAX4374/ MAX4375 is latched to provide a turn-off flag that doesn t oscillate. In addition, the MAX4374/MAX4375 contain a second comparator for use in window-detection functions. The are available in three different gain versions (T = +/, F = +5/, H = +/) and use an external sense resistor to set the sensitivity of the input voltage to the load current. These features offer a high level of integration, resulting in a simple and compact currentsense solution. The operate from a single +.7 to +8 supply and consume 5µA. They are specified for the extended operating temperature range (-4 C to +85 C) and are available in 8-pin and -pin µmax packages. Applications Notebook Computers Portable/Battery-Powered Systems Smart Battery Packs/Chargers Cell Phones Power-Management Systems General-System/Board-Level Current Monitoring Precision Current Sources Features Current-Sense Amplifier plus Internal Comparator and Bandgap Reference with Improved Accuracy 5µA Supply Current Single +.7 to +8 Operating Supply m (max) Input Offset oltage % (max) Full-Scale Accuracy Internal Bandgap Reference (±.6% Accuracy) Latching Comparator Output Three Gain ersions Available (+/, +5/, +/) Wide to +8 Common-Mode Range, Independent of Supply oltage PART IN = TO 8 =.7 TO 8 C.µF Ordering Information TEMP RANGE + SENSE - R SENSE MAX4373 PIN- PACKAGE Ordering Information continued at end of data sheet. I LOAD LOAD/ BATTERY GAIN (/) MAX4373TEUA -4 C to +85 C 8 µmax + MAX4373TESA -4 C to +85 C 8 SO + MAX4373FEUA -4 C to +85 C 8 µmax +5 MAX4373FESA -4 C to +85 C 8 SO +5 MAX4373HEUA -4 C to +85 C 8 µmax + MAX4373HESA -4 C to +85 C 8 SO + Typical Operating Circuit PULL-UP (UP TO 5) R3 C CIN R R Pin Configurations appear at end of data sheet. Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS,, to to +3 to to the lesser of ( +.3) or +5 CIN, CIN, to to the lesser of ( +.3) or + Differential Input oltage ( RS + - RS -)...±.3 C, C to to +6. Current into Any Pin...±mA 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 Continuous Power Dissipation (T A = +7 C) 8-Pin µmax (derate 4.mW/ C above +7 C)...33mW 8-Pin SO (derate 5.9mW/ C above +7 C)...47mW -Pin µmax (derate 5.6mW/ C above +7 C)...444mW 4-Pin SO (derate 8.3mW/ C above +7 C)...667mW Operating Temperature Range...-4 C to +85 C Junction Temperature...+5 C Storage Temperature Range C to +5 C Lead Temperature (soldering, s)...+3 C ( = +.7 to +8, = to +8, SENSE =, =, R LOAD = MΩ, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) (Note ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating oltage Range (Note ).7 8 = T A = T MIN to T MAX Common-Mode Input Range (Note 3) CMR 8 Common-Mode Rejection CMR > 85 db Supply Current I CC >, SENSE = 5m 5 µa Leakage Current I, I = ±.5 ±.5 µa Input Bias Current I >.5-5. I > µa Full-Scale Sense oltage Gain = +/, +5/ 5 7 (Note 4) SENSE Gain = +/ m Input Offset oltage OS = = T A = +5 C. (Note ) T A = T MIN to T MAX m =, T A = +5 C ±.3 ± SENSE = ±3 m = 8, T A = +5 C ±.35 ± Total oltage Error (Note 6) = 8 T A = T MIN to T MAX ±3 (Note 5) % =, =. ±5. SENSE = 6.5m, =, = (Note 7) I = µa.5 oltage Low =.7 I = µa ±5. m oltage High -.5 =.7, I = -5µA OH

3 ELECTRICAL CHARACTERISTICS (continued) ( = +.7 to +8, = to +8, SENSE =, =, R LOAD = MΩ, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) (Note ) -3dB Bandwidth Gain Gain Accuracy PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Settling Time to % of Final alue SENSE = m to m, =, =, Gain = T A = +5 C T A = -4 C to +85 C ±.3 ±.7 Capacitive Load Stability No sustained oscillations pf Output Resistance R SENSE = m.5 Ω Power-Supply Rejection PSR =, > 7 87 db Power-Up Time to % of Final alue BW SENSE = m, Gain = +/ SENSE = m, Gain = +5/ SENSE = m, Gain = +/ SENSE = 6.5m 5 MAX437_T + A MAX437_F MAX437_H +5 + A =, =, C LOAD = pf SENSE = m to 5m; = ; = ; Gain =, 5 Gain = +/, =, =, C LOAD = pf T A = +5 C SENSE = m, C LOAD = pf, =, = T A = -4 C to +85 C SENSE = 6.5m to m SENSE = m to 6.5m Saturation Recovery Time (Note 8) =, =, C LOAD = pf. ms COMPARATOR (Note 9) Comparator Threshold TH T A = +5 C T A = T MIN to T MAX m Comparator Hysteresis -9 m Input Bias Current I B ±. ±5 na C Propagation Delay L = pf, R L = kω pull-up to 5, 4 µs 5m of overdrive Output Low oltage OL I SINK = ma.6 ±.3 ±.7.5 ±.7 ±.7 khz / % µs ms 3

4 ELECTRICAL CHARACTERISTICS (continued) ( = +.7 to +8, = to +8, SENSE =, =, R LOAD = MΩ, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +5 C.) (Note ) PARAMETER Output High Leakage Current Input High oltage Input Low oltage Logic Input Current Minimum Pulse Width Propagation Delay SYMBOL IH IL I IL, I IH t RPW t RPD CONDITIONS = 8, PULL-UP = 5 (Note ) MIN TYP MAX Note : All devices are % production tested at T A = +5 C. All temperature limits are guaranteed by design. Note : Guaranteed by PSR test. Note 3: Guaranteed by oltage Error test. Note 4: Guaranteed by Gain Accuracy test. Output voltage is internally clamped not to exceed. Note 5: Total oltage Error and Full-Scale Accuracy are the sum of gain and offset voltage errors. Note 6: Measured at I = -5µA (R LOAD = 4kΩ for gain of +/, R LOAD = kω for gain of +5/, R LOAD = kω for gain of +/). Note 7: +6.5m = /6 of +m full-scale voltage. Note 8: The device will not experience phase reversal when overdriven. Note 9: All comparator tests are done with = +. Note : PULL-UP is defined as an externally applied voltage through a resistor to pull up the comparator output. Note : OS is extrapolated from the gain accuracy test. UNITS IL =, IH = 5.5, = µa µa µs µs Typical Operating Characteristics ( = +, = +, R LOAD = MΩ, =, SENSE = m, PULL-UP = +5, R PULL-UP = kω, T A = +5 C, unless otherwise noted.) SUPPLY CURRENT (µa) SENSE = 5m SUPPLY CURRENT vs. SUPPLY OLTAGE MAX4374/MAX4375 MAX SUPPLY OLTAGE () MAX4373 toc SUPPLY CURRENT (µa) SUPPLY CURRENT vs. COMMON-MODE OLTAGE SENSE = 5m MAX4374/MAX4375 MAX COMMON-MODE OLTAGE () MAX4373 toc ERROR (%) A = +5/ SENSE = m TOTAL ERROR vs. SUPPLY OLTAGE A = +/ A = +/ SUPPLY OLTAGE () MAX4373 toc3 4

5 Typical Operating Characteristics (continued) ( = +, = +, R LOAD = MΩ, =, SENSE = m, PULL-UP = +5, R PULL-UP = kω, T A = +5 C, unless otherwise noted.) ERROR (%) A = +/ TOTAL ERROR vs. SUPPLY OLTAGE A = +5/ A = +/ SENSE = 6.5m SUPPLY OLTAGE () ERROR (%) MAX4373 toc4 ERROR (%) TOTAL ERROR vs. SENSE OLTAGE A = +/ A = +/ = +5.5 A = +/ TOTAL ERROR vs. SENSE OLTAGE A = +5/ A = +/ SENSE (m) = +8 A = +5/ MAX4373 toc7 ERROR (%) MAX4373 toc5 ERROR (%) TOTAL ERROR vs. SENSE OLTAGE A = +/ A = +5/ A = +/ SENSE (m) TOTAL ERROR vs. COMMON-MODE OLTAGE A = +/ A = +5/ MAX4373 toc8 MAX4373 toc SENSE (m) - A = +/ COMMON-MODE OLTAGE () SMALL-SIGNAL PULSE RESPONSE (A = +/) MAX4373 toc9 SMALL-SIGNAL PULSE RESPONSE (A = +5/) MAX4373 toc SMALL-SIGNAL PULSE RESPONSE (A = +/) MAX4373 toc 3m 3m 3m m m m 6m m.5 5m 3 µs/div µs/div µs/div 5

6 Typical Operating Characteristics (continued) ( = +, = +, R LOAD = MΩ, =, SENSE = m, PULL-UP = +5, R PULL-UP = kω, T A = +5 C, unless otherwise noted.) LARGE-SIGNAL PULSE RESPONSE (A = +/) CMR (db) µs/div MAX4373 toc 5m 5m 3 COMMON-MODE REJECTION vs. FREQUENCY k k k FREQUENCY (Hz) LARGE-SIGNAL PULSE RESPONSE (A = +5/) MAX4373 toc3 MAX4373 toc5 µs/div PSR (db) m 5m LARGE-SIGNAL PULSE RESPONSE (A = +/) POWER-SUPPLY REJECTION vs. FREQUENCY µs/div - k k k FREQUENCY (Hz) MAX4373 toc6 MAX4373 toc4 95m 5m 9.5 5m GAIN (db) k SMALL-SIGNAL GAIN vs. FREQUENCY A = +5/ A = +/ k k FREQUENCY (Hz) A = +/ MAX4373 toc7 k LARGE-SIGNAL GAIN vs. FREQUENCY -5 k k k FREQUENCY (Hz) 6 GAIN (db) IN = mp-p (, 5) IN = 5mp-p () A = +/ A = +/ A = +5/ MAX4373 toc8

7 Typical Operating Characteristics (continued) ( = +, = +, R LOAD = MΩ, =, SENSE = m, PULL-UP = +5, R PULL-UP = kω, T A = +5 C, unless otherwise noted.) TRIP POINT (m) A = +/ POWER-UP DELAY µs/div COMPARATOR TRIP POINT vs. SUPPLY OLTAGE MAX4373 toc SUPPLY OLTAGE () MAX4373 toc 6 5m/div.5/div COMPARATOR POWER-UP DELAY = PULL-UP COMPARATOR PROPAGATION DELAY OD = 5m µs/div µs/div MAX4373 toc MAX4373 toc 5 5 PROGAGATION DELAY (µs) COMPARATOR PROPAGATION DELAY vs. OERDRIE OLTAGE MAX4373 toc4 PROPAGATION DELAY (µs) COMPARATOR PROPAGATION DELAY vs. TEMPERATURE OD = 5m MAX4373 toc OERDRIE OLTAGE (m) TEMPERATURE ( C) 7

8 Typical Operating Characteristics (continued) ( = +, = +, R LOAD = MΩ, =, SENSE = m, PULL-UP = +5, R PULL-UP = kω, T A = +5 C, unless otherwise noted.) OLTAGE () COMPARATOR OLTAGE vs. SUPPLY OLTAGE SUPPLY OLTAGE () COMPARATOR AC RESPONSE µs/div MAX4373 toc3 75m 5m 5 SUPPLY CURRENT (µa) MAX4373 toc OL (m) SUPPLY CURRENT vs. TEMPERATURE MAX4374 MAX4375 SENSE = 5m MAX TEMPERATURE ( C) COMPARATOR OL vs. I SINK MAX4373 toc3 I SINK (ma) TOTAL ERROR (%) MAX4373 toc8 TOTAL ERROR vs. TEMPERATURE TEMPERATURE ( C) MAX4373 toc33 GAIN ACCURACY (%) GAIN ACCURACY vs. TEMPERATURE A = +/, +5/ A = +/ TEMPERATURE ( C) MAX4373 toc34 COMPARATOR TRIP POINT (m) COMPARATOR TRIP POINT vs. TEMPERATURE TEMPERATURE ( C) MAX4373 toc35 8

9 PIN MAX4373 MAX4374/MAX4375 NAME µmax/so µmax SO CIN 4 5 CIN C 7 C , 6, 9, N.C. Supply oltage Input FUNCTION FUNCTION Pin Description oltage Output. is proportional to SENSE ( - ). Comparator Input. Positive input of an internal comparator. The negative terminal is connected to a.6 internal reference. Comparator Input. Terminal of a second internal comparator. The positive terminal for the MAX4374 and the negative terminal for the MAX4375. The other terminal is connected to a.6 internal reference. Ground Reset Input. Resets the output latch of the comparator at CIN. Open-Drain Comparator Output. Latching output of the comparator controlled by CIN. Connect to to disable the latch. Open-Drain Comparator Output. Output of the second unlatched internal comparator. Load-Side Connection for the External Sense Resistor Power Connection to the External Sense Resistor No Connection. Not internally connected. IN = TO 8 PULL-UP (UP TO 5) R3 PULL-UP (UP TO 5) R6 C C Figure. Functional Diagram + SENSE - R SENSE CURRENT- SENSE AMPLIFIER + - +(-) -(+).6 BANDGAP REFERENCE MAX4374 (MAX4375) CIN CIN LOAD R R4 R R5 Detailed Description The MAX4373 high-side current-sense supervisor features a high-side current-sense amplifier, bandgap reference, and comparator with latching output to monitor a supply for an overcurrent condition (Figure ). The latching output allows the comparator to shut down a power supply without oscillations. The MAX4374/ MAX4375 offer an additional comparator to allow window detection of the current. Current-Sense Amplifier The internal current-sense amplifier features a to +8 input common-mode range that is independent of the supply voltage. With this feature, the device can monitor the output current of a battery in deep discharge and also high-side current-sensing voltages exceeding. The current-sense amplifier is also suitable for low-side current sensing. However, the total output voltage error will increase when falls below, as shown in the Electrical Characteristics and Typical Operating Characteristics. 9

10 Internal Comparator(s) The contain an opendrain output comparator for current limiting. The comparator s negative terminal is connected to the internal 6m reference. The positive terminal is accessible at CIN. When is high, the internal latch is active, and once CIN rises above 6m, the output latches into the open state. Pulsing low for.5µs resets the latch, and holding low makes the latch transparent. See at Power-Up section The MAX4374/MAX4375 contain an additional opendrain comparator. The negative terminal of the MAX4374 s additional comparator and the positive terminal of the MAX4375 s additional comparator are connected to the internal 6m reference as shown in Figure. The positive terminal of the MAX4374 s additional comparator and the negative terminal of the MAX4375 s additional comparator are accessible at CIN. Applications Information Recommended Component alues Ideally, the maximum load current will develop the fullscale sense voltage across the current-sense resistor. Choose the gain version needed to yield the maximum output voltage required for the application: = SENSE A where SENSE is the full-scale sense voltage, 5m for gains of +/ and +5/ or m for a gain of +/. A is the gain of the device. The minimum supply voltage is +.5. Note that the output for the gain of +/ is internally clamped at. Calculate the maximum value for R SENSE so that the differential voltage across and does not exceed the full-scale sense voltage: R SENSE( MAX) = SENSE( MAX) I LOAD Choose the highest value resistance possible to maximize SENSE and thus minimize total output error. In applications monitoring high current, ensure that R SENSE is able to dissipate its own I R loss. If the resistor s power dissipation is exceeded, its value may drift or it may fail altogether, causing a differential voltage across the terminals in excess of the absolute maximum ratings. Use resistors specified for current-sensing applications..7 TO 5.5 PUSHBUTTON R C C MAX4373 Overcurrent Protection Circuit The overcurrent protection circuit, shown in Figure, uses the MAX4373 to control an external P-channel MOSFET. The MOSFET controlled by the MAX4373 opens the current path under overload conditions. The latched output of the MAX4373 s comparator prevents the circuit from oscillating, and the pushbutton resets the current path after an overcurrent condition. Window Detection Circuit Figure 3 shows a simple circuit suitable for window detection. Let I OER be the minimum load current (I LOAD ) required to cause a low state at C, and let I UNDER be the maximum load current required to cause a high state at C: where A is the gain of the device and REF is the internal reference voltage (.6 typ). Connect C and C; the resulting comparator output will be high when the current is inside the current window and low when the current is outside the window. The window is defined as load currents less than I OER and greater than I UNDER. CIN Figure. MAX4373 Overcurrent Protection Circuit and I I UNDER OER = = R R REF SENSE REF SENSE A A LOAD R4 + R5 R5 R + R R

11 =.7 TO 8 PULL-UP (UP TO 5) IN = TO 8 R3 MAX4375 C C + SENSE - R SENSE Figure 3. MAX4375 Window Detector Power-Supply Bypassing It is recommended that CC be bypassed to with at least a.µf ceramic capacitor to isolate the IC from supply voltage transients. It is possible that plugging in/out a battery or AC adapter/charger could cause large, fast line transients (>5/µs) at CC. The simplest solution is to run CC from a better regulated supply (+5 for example), since CC and (or ) do not have to be connected together. For high-speed CC transients, another solution is to add a resistor in series with the CC pin and a.µf capacitor to create an RC time constant to slow the rise time of the transient. Since these current-sense amplifiers consume less than µa, even a.5kω resistor only drops an extra 5m at CC. For most applications with fast transients, kω in conjunction with a.µf bypass capacitor works well. CIN CIN I LOAD LOAD R R R4 R5 at Power-Up The pin is used to control the latch function of comparator. Holding low (<.8) makes the latch transparent and C will respond to changes at CIN, above and below the internal 6m reference threshold voltage. When is high (>.), once CIN rises above 6m, C latches into the open-drain OFF state and remains in this state even if CIN drops below 6m. Pulsing low for at least.5µs resets the latch. There is no internal circuitry to control the reset function during power-up. To prevent false latching, must be held low until the power has risen above the.7 minimum operating supply voltage. This is easily accomplished when is driven under µc or logic gate control. However, if is to be always connected high, add an RC between, and (see Figure ). Note that cannot exceed +.3 or +, whichever is less. The following formula can be used to determine the appropriate RC value. T T RC = ln 7. /( ) 354. ( ) = where T is the maximum time for to reach.7 and.8 is the maximum logic low voltage. For example, a 47kΩ resistor and.µf capacitor will keep low during a power-up time of up to 36ms. A faster power-up time is also safe with the calculated R and C since the capacitor will have even less time to charge.

12 TOP IEW Ordering Information (continued) PART CIN 3 4 MAX4373 µmax/so TEMP RANGE PIN- PACKAGE GAIN (/) MAX4374TEUB -4 C to +85 C µmax + MAX4374TESD -4 C to +85 C 4 SO + MAX4374FEUB -4 C to +85 C µmax +5 MAX4374FESD -4 C to +85 C 4 SO +5 MAX4374HEUB -4 C to +85 C µmax + MAX4374HESD -4 C to +85 C 4 SO + MAX4375TEUB -4 C to +85 C µmax + MAX4375TESD -4 C to +85 C 4 SO + MAX4375FEUB -4 C to +85 C µmax +5 MAX4375FESD -4 C to +85 C 4 SO +5 MAX4375HEUB -4 C to +85 C µmax + MAX4375HESD -4 C to +85 C 4 SO N.C. C CIN 3 CIN 4 5 MAX4374 MAX4375 µmax N.C. 3 CIN 4 CIN 5 N.C. 6 7 SO Chip Information TRANSISTOR COUNT: 39 SUBSTRATE CONNECTED TO Pin Configurations MAX4374 MAX C C C C N.C.

13 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 A.6±. 8 e ÿ.5±. D TOP IEW FRONT IEW e ÿ.5±..6±. TOP IEW b E A H A 4X S H c 4X S L BOTTOM IEW SIDE IEW 8 BOTTOM IEW α DIM A A PROPRIETARY INFORMATION TITLE: PACKAGE LINE, 8L umax/usop APPROAL INCHES MIN MAX BSC A.3 b c D e E.6 H.88 L.6 α S.7 BSC S α MILLIMETERS MIN MAX BSC BSC DOCUMENT CONTROL NO. INCHES RE. -36 J DIM A A MIN -. MAX.43.6 MIN -.5 MAX..5 A D D E E H L L b e c MILLIMETERS REF.94 REF BSC.5 BSC REF.498 REF 6 6 8LUMAXD.EPS LUMAX.EPS D E GAGE PLANE A A c D b A α E L L FRONT IEW SIDE IEW PROPRIETARY INFORMATION TITLE: PACKAGE LINE, L umax/usop DOCUMENT CONTROL NO. -6 I 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, San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. APPROAL RE.