Datasheet MAX4373, MAX4374, MAX4375 (Maxim) - 10

MAX4373/MAX4374/MAX4375 Low-Cost, Micropower, High-Side Current-Sense Amplifier + Comparator + Reference ICs
Internal Comparator(s)
The MAX4373/MAX4374/MAX4375 contain an open- drain output comparator for current limiting. The com- parator’s negative terminal is connected to the internal LOAD 600mV reference. The positive terminal is accessible at RS+ RS- CIN1. When RESET is high, the internal latch is active, 2.7V TO 5.5V and once CIN1 rises above 600mV, the output latches COUT1 OUT into the open state. Pulsing RESET low for 1.5µs resets the latch, and holding RESET low makes the latch VCC transparent. See RESET at Power-Up section MAX4373 The MAX4374/MAX4375 contain an additional open- R drain comparator. The negative terminal of the CIN1 MAX4374’s additional comparator and the positive ter- RESET minal of the MAX4375’s additional comparator are con- nected to the internal 600mV reference as shown in PUSHBUTTON C Figure 1. The positive terminal of the MAX4374’s addi- tional comparator and the negative terminal of the MAX4375’s additional comparator are accessible at GND CIN2.
Applications Information
Figure 2. MAX4373 Overcurrent Protection Circuit
Recommended Component Values
Ideally, the maximum load current will develop the full-
Overcurrent Protection Circuit
scale sense voltage across the current-sense resistor. The overcurrent protection circuit, shown in Figure 2, uses the MAX4373 to control an external P-channel MOSFET. The MOSFET controlled by the MAX4373 VOUT = VSENSE × A opens the current path under overload conditions. The V latched output of the MAX4373’s comparator prevents Choose the gain version needed to yield the maximum the circuit from oscillating, and the pushbutton resets output voltage required for the application: the current path after an overcurrent condition. where VSENSE is the full-scale sense voltage, 150mV for
Window Detection Circuit
gains of +20V/V and +50V/V or 100mV for a gain of Figure 3 shows a simple circuit suitable for window +100V/V. AV is the gain of the device. The minimum detection. Let IOVER be the minimum load current supply voltage is VOUT + 0.25V. Note that the output for the gain of +100V/V is internally clamped at 12V. VREF ⎛ R4 R5⎞ IUNDER = + R SENSE × AV ⎝ ⎜ R5 ⎠⎟ VSENSE MAX ( ) RSENSE MAX ( ) = and ILOAD VREF ⎛ R 1 R2 ⎞ IOVER = + Calculate the maximum value for RSENSE so that the R SENSE × AV ⎝ ⎜ R2 ⎠⎟ differential voltage across RS+ and RS- does not exceed the full-scale sense voltage: (ILOAD) required to cause a low state at COUT2, and let Choose the highest value resistance possible to maxi- IUNDER be the maximum load current required to cause mize VSENSE and thus minimize total output error. a high state at COUT1: In applications monitoring high current, ensure that where AV is the gain of the device and VREF is the inter- RSENSE is able to dissipate its own I2R loss. If the resis- nal reference voltage (0.6V typ). tor’s power dissipation is exceeded, its value may drift Connect COUT1 and COUT2; the resulting comparator or it may fail altogether, causing a differential voltage output will be high when the current is inside the cur- across the terminals in excess of the absolute maxi- rent window and low when the current is outside the mum ratings. Use resistors specified for current-sens- window. The window is defined as load currents less ing applications. than IOVER and greater than IUNDER. www.maximintegrated.com Maxim Integrated | 10