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SLAU880C December 2022 – May 2024 ULC1001

5.2.2.1 Voltage and Current Sense Circuitry

Each input into the ULC1001 current and voltage sense amplifiers require a voltage divider to decrease the high voltage across the transducer from 0V to 0.9V. The circuit representation of the current and voltage sense amplifiers is shown in Figure 5-9, where the items in I-sense Amp and V-sense Amp are internal to ULC1001. The resistors used in the voltage dividers must have a 0.1% tolerance to achieve high accuracy for power measurements. Three scale factors, USER_Params_ohms_sf_Q22, USER_Params_watts_sf_Q18, and USER_Params_Imag_max_sf_Q27, are used to convert the measured values into power, impedance, and current values, respectively. Use the below equation to determine the scale factors and the current and voltage sense amplifier gains. Table 5-6 containing typical resistor values for common voltage levels.

Note: The equivalent resistance between VDD and GND must be ≥ 4kΩ. R_F is fixed to 84kΩ.

ULC1001 DRV2901 ULC1001-DRV-FL-EVM ULC1001-DRV290XEVM Voltage and Current Sense Amplifiers

Figure 5-9 Voltage and Current Sense Amplifiers

Equation 2.

U S E R_P a r a m s_o h m s_s f_Q 22 = \frac{{I S N S}_{G A I N}}{{V S N S}_{G A I N}}

Equation 3.

U S E R_P a r a m s_w a t t s_s f_Q 18 = \frac{1}{{V S N S}_{G A I N}} ✕ \frac{1}{{I S N S}_{G A I N}} ✕ 0.2025

Equation 4.

U S E R_P a r a m s_I m a g_m a x_s f_Q 27 = \frac{0.9}{{I S N S}_{G A I N}}

Equation 5.

{I S N S}_{G A I N} (\frac{V}{A}) = \frac{R_{f} ✕ R_{S N S}}{R_{4}}

Equation 6.

{V S N S}_{G A I N} (\frac{V}{V}) = 1.043 ✕ \frac{R_{f}}{R_{1} {✕ R}_{3} ✕ (\frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}})}

Table 5-6 Voltage and Current Sense Resistor Reference Values R5 = 6kΩ. R6 = 2kΩ

Differential Voltage (pk-pk)	R1	R2	R3	R4
460	1.3MΩ	6.34kΩ	294kΩ	422kΩ
90	360kΩ	30kΩ	1MΩ	150kΩ
40	150kΩ	30kΩ	1MΩ	150kΩ