Datasheet MAX4172 (Maxim) - 6
| Fabricante | Maxim |
| Descripción | Low-Cost, Precision, High-Side Current-Sense Amplifier |
| Páginas / Página | 9 / 6 — MAX4172. Current Output. PG Output. Applications Information. Suggested … |
| Revisión | 4 |
| Formato / tamaño de archivo | PDF / 1.6 Mb |
| Idioma del documento | Inglés |
MAX4172. Current Output. PG Output. Applications Information. Suggested Component Values. for Various Applications
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link to page 3 link to page 1 link to page 7 MAX4172 Low-Cost, Precision, High-Side Current-Sense Amplifier ILOAD x RSENSE. Then, since IRG1 flows through RG1, IRG1 x RG1 = ILOAD x RSENSE. The internal current mirror multiplies IRG1 by a factor of 50 to give IOUT = 50 x IRG1. RSENSE ILOAD Substituting IOUT/50 for IRG1, (IOUT/50) x RG1 = ILOAD INPUT TO LOAD/ x RSENSE, or: BATTERY IOUT = 50 x ILOAD x (RSENSE/RG1) RS+ VSENSE RS- The internal current gain of 50 and the factory-trimmed resistor R RG1 RG2 G1 combine to result in the device’s transcon- ductance (Gm) of 10mA/V. Gm is defined as being equal to IOUT/(VRS+ - VRS-). Since (VRS+ - VRS-) = ILOAD x IRG1 RSENSE, the output current (IOUT) can be calculated with A1 the following formula: IOUT = Gm x (VRS+ - VRS-) =
MAX4172
(10mA/V) x (ILOAD x RSENSE) Q1 V+
Current Output
The output voltage equation for the MAX4172 is given 1:50 IOUT = 50 IRG1 CURRENT OUT below: MIRROR VOUT = (Gm) x (RSENSE x ROUT x ILOAD) where V V+ OUT = the desired full-scale output voltage, ILOAD equals the full-scale current being sensed, R PG SENSE equals the current-sense resistor, ROUT equals the voltage-setting resistor, and Gm equals the device’s VTH transconductance (10mA/V). GND The full-scale output voltage range can be set by changing the ROUT resistor value, but the output voltage must be no greater than V+ - 1.2V. The above equation can be modified to determine the R Figure 1. Functional Diagram OUT required for a particular full-scale range: ROUT = (VOUT)/(ILOAD x RSENSE x Gm) OUT is a high-impedance current source that can be systems by ensuring that the components in the control integrated by connecting it to a capacitive load. loop have sufficient voltage to operate correctly.
PG Output Applications Information
The PG output is an open-collector logic output that
Suggested Component Values
indicates the status of the MAX4172’s V+ power supply. A
for Various Applications
logic low on the PG output indicates that V+ is sufficient to The Typical Operating Circuit is useful in a wide variety of power the MAX4172. This level is temperature dependent applications. Table 1 shows suggested component values (see Typical Operating Characteristics graphs), and is and indicates the resulting scale factors for various applications typically 2.7V at room temperature. The internal PG required to sense currents from 100mA to 10A. comparator has a 100mV (typ) hysteresis to prevent possible oscillations caused by repeated toggling of the Adjust the RSENSE value to monitor higher/lower current PG output, making the device ideal for power-management levels. Select RSENSE using the guidelines and formulas systems lacking soft-start capability. An internal delay in the following section. (15μs, typ) in the PG comparator allows adequate time for power-on transients to settle out. The PG status indicator greatly simplifies the design of closed-loop www.maximintegrated.com Maxim Integrated │ 6
MAX4172
(10mA/V) x (ILOAD x RSENSE) Q1 V+
Current Output
The output voltage equation for the MAX4172 is given 1:50 IOUT = 50 IRG1 CURRENT OUT below: MIRROR VOUT = (Gm) x (RSENSE x ROUT x ILOAD) where V V+ OUT = the desired full-scale output voltage, ILOAD equals the full-scale current being sensed, R PG SENSE equals the current-sense resistor, ROUT equals the voltage-setting resistor, and Gm equals the device’s VTH transconductance (10mA/V). GND The full-scale output voltage range can be set by changing the ROUT resistor value, but the output voltage must be no greater than V+ - 1.2V. The above equation can be modified to determine the R Figure 1. Functional Diagram OUT required for a particular full-scale range: ROUT = (VOUT)/(ILOAD x RSENSE x Gm) OUT is a high-impedance current source that can be systems by ensuring that the components in the control integrated by connecting it to a capacitive load. loop have sufficient voltage to operate correctly.
PG Output Applications Information
The PG output is an open-collector logic output that
Suggested Component Values
indicates the status of the MAX4172’s V+ power supply. A
for Various Applications
logic low on the PG output indicates that V+ is sufficient to The Typical Operating Circuit is useful in a wide variety of power the MAX4172. This level is temperature dependent applications. Table 1 shows suggested component values (see Typical Operating Characteristics graphs), and is and indicates the resulting scale factors for various applications typically 2.7V at room temperature. The internal PG required to sense currents from 100mA to 10A. comparator has a 100mV (typ) hysteresis to prevent possible oscillations caused by repeated toggling of the Adjust the RSENSE value to monitor higher/lower current PG output, making the device ideal for power-management levels. Select RSENSE using the guidelines and formulas systems lacking soft-start capability. An internal delay in the following section. (15μs, typ) in the PG comparator allows adequate time for power-on transients to settle out. The PG status indicator greatly simplifies the design of closed-loop www.maximintegrated.com Maxim Integrated │ 6