STEVAL-IHP001V3 STMicroelectronics, STEVAL-IHP001V3 Datasheet - Page 19

• Manufacturer Part Number: STEVAL-IHP001V3
• Description: BOARD SMART PLUG STM32 SPZB260PR
• Manufacturer: STMicroelectronics
• Series: Zigbee™ SmartPlugr
• Type: Microcontroller, Energy Meteringr

Specifications of STEVAL-IHP001V3

• Frequency: 2.4GHz
• For Use With/related Products: STM32F10x, SPZB260-PRO, STPM01
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-10677

STPM01
8.3
Figure 14. First order ∑ Δ A/D converter
8.4
∑Δ A/D converters
The analog to digital conversion in the STPM01 is carried out using two first order ∑ Δ
converters. The device performs A/D conversions of analog signals on two independent
channels in parallel. The current channel is multiplexed as primary or secondary current
channel in order to be able to perform a tamper function, if it is enabled. The converted ∑ Δ
signals are supplied to the internal hardwired DSP unit, which filters and integrates those
signals in order to boost the resolution and to yield all the necessary signals for
computations.
A ∑ Δ modulator converts the input signal into a continuous serial stream of 1 s and 0 s at a
rate determined by the sampling clock. In the STPM01, the sampling clock is equal to f
The 1-bit DAC in the feedback loop is driven by the serial data stream. The DAC output is
subtracted from the input signal. If the loop gain is high enough, the average value of the
DAC output (and therefore the bit stream) can approach that of the input signal level. When
a large number of samples are averaged a very precise value of the analog signal is
obtained. This averaging is carried out in the DSP section which implements decimation,
integration and DC offset cancellation of the supplied ∑ Δ signals. The gain of the
decimation filters is 1.004 for the voltage channel and 0.502 for the current channel. The
resulting signal has a resolution of 11bits for voltage channel and 16 bits for current
channel.
Zero crossing detection
The STPM01 has a zero crossing detector circuit on the voltage channel which can be used
by application for synchronization of some utility equipment to event of zero crossing of line
voltage. This circuit produces the internal signal ZCR which has a rising edge every time the
line voltage crosses zero and a negative edge every time the voltage reaches its positive or
negative peak. The ZCR signal is then at twice the line voltage frequency. The ZCR signal is
available on the MOP pin only when STPM01 works as peripheral with the configuration bit
APL = 0.
Input analog signal
+
Σ
-
Doc ID 10853 Rev 7
Integrator
∫
DAC
f
CLK
/4
Output digital signal
Theory of operation
CLK/4
19/60
.