ZHCSOF7B 数据表 | 德州仪器 TI.com.cn

ZHCSOF7B september 2022 – june 2023 TPS25990

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RQP|26
- MPQF569A

散热焊盘机械数据 (封装 | 引脚)

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8.3.14.7.1.30 READ_EIN (86h, Block Read)

The READ_EIN command is a standard PMBus® command which returns information to the host for computing the accumulated energy and average power consumption by a system powered by the eFuse. The information provided by this command is independent of any device specific averaging period, sampling frequency, or calculation algorithm.

This command uses the PMBus® block read protocol with a block size of six (6).

This command returns six (6) bytes of data. The first two (2) bytes are the two's complement and signed output of an accumulator that continuously sums samples of the instantaneous input power (the product of the samples of the input voltage and input current). These two data bytes are encoded in the DIRECT format as described in Section 8.3.14.10. The accumulator values are scaled so that the units are in “watt-samples”. This value in “watt-samples” must be multiplied by the effective ADC sampling period to obtain the real world value of energy accumulation in joules. If Bit[3] of the DEVICE_CONFIG register is set to high, the effective ADC sampling period is 18 µs (typical). Otherwise, it will be 11 µs (typical) by default.

The third data byte, ROLLOVER_COUNT is a count of rollover events for the accumulator. This byte is an unsigned integer indicating the number of times the accumulator has rolled over from its maximum positive value of 7FFFh to zero. The ROLLOVER_COUNT will periodically roll over from its maximum positive value to zero. It is up to the host to keep track of the state of the ROLLOVER_COUNT and account for the rollovers.

The other three (3) data bytes are a 24-bit unsigned integer that counts the number of samples of the instantaneous input power accumulated till now. This value will also roll over periodically from its maximum positive value to zero.

The combination of the accumulator and the rollover count may overflow within a few seconds. It is left to the host software to detect this overflow and handle it appropriately. Similarly, the sample count value will overflow. However, this event only occurs every five (5) minutes if Bit[3] of the DEVICE_CONFIG register is set to high, otherwise every three (3) minutes.

Table 8-25 READ_EIN Register Description

BYTE	Description	DEFAULT	Access
0	Power Accumulator Low Byte	0x00	Read
1	Power Accumulator High Byte	0x00
2	Power Accumulator Rollover Count	0x00
3	Sample Count Low byte	0x00
4	Sample Count Mid byte	0x00
5	Sample Count High byte	0x00

The host uses the accumulator value and rollover count to calculate the current “energy count” in “watt-samples” using Equation 15.

Equation 15.

E n e r g y_C o u n t = (R o l l o v e r_C o u n t \times A c c u m u l a t o r_R o l l_O v e r_V a l u e) + A c c u m u l a t o r_V a l u e

Where the Accumulator_Roll_Over_Value is the maximum possible positive value of the accumulator plus one (1). It is necessary to add one (1) to the maximum accumulator value to make the average power calculation correctly. The Accumulator_Roll_Over_Value is calculated using Equation 16.

Equation 16.

A c c u m u l a t o r_R o l l_O v e r_V a l u e = \frac{1}{m} [\{(Y_{M A X} + 1) {\times 10}^{- R}\} - b] = \frac{1}{m} [\{(2^{15}) {\times 10}^{- R}\} - b]

Table 8-67 includes the "m, b, R" coefficients used in Equation 16. Accumulator_Value is obtained using the coefficients in Table 8-67 and Equation 19. The real world value of energy accumulation in joules is calculated using Equation 17.

Equation 17.

A c c u m u l a t e d_E n e r g y = E n e r g y_C o u n t \times E f f e c t i v e_A D C_S a m p l i n g_P e r i o d

If Bit[3] of the DEVICE_CONFIG register is set to high, the Effective_ADC_Sampling_Period is 18 µs (typical). Otherwise, it will be 11 µs (typical) by default. The host calculates the average power in watt since the last reading using Equation 18.

Equation 18.

A v e r a g e_P o w e r = \frac{C u r r e n t_E n e r g y_C o u n t - L a s t_E n e r g y_C o u n t}{C u r r e n t_S a m p l e_C o u n t - L a s t_S a m p l e_C o u n t}

Note:

The ADC HI PERF bit in the DEVICE_CONFIG register) defines the ADC internal operating modes. The effective ADC sampling period is 11 µs in normal mode and 18 µs in high performance mode. The device is configured for normal mode by default. If it is necessary to change the ADC internal modes, it must be done before the downstream loads are enabled. It should not be changed under normal operation. This results in the wrong real world value for energy accumulation.