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MAX34407EWE+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17
Bits 23 to 0: CNT23 to CNT0
These bits report the number of times the accumulators have been updated. Send the UPDATE command before read-
ing this register. By dividing the total accumulated power reported in each power accumulator by this count, the average
power can be determined. The accumulator counter does not roll over. If the accumulator counter overflows, the OVF bit
in the CONTROL command is set and remains set until the UPDATE command is sent.
Table 8. Accumulator Counter (02h)—Block Read
Table 9. Power Accumulator for Channel 1 (03h)—Block Read
Power Accumulator for Channel 2 (04h)—Block Read
Power Accumulator for Channel 3 (05h)—Block Read
Power Accumulator for Channel 4 (06h)—Block Read
BIT 23 BIT 22 BIT 21 BIT 20 BIT 19 BIT 18 BIT 17 BIT 16
NAME: CNT23 CNT22 CNT21 CNT20 CNT19 CNT18 CNT17 CNT16
POR: 0 0 0 0 0 0 0 0
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8
NAME: CNT15 CNT14 CNT13 CNT12 CNT11 CNT10 CNT9 CNT8
POR: 0 0 0 0 0 0 0 0
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NAME: CNT7 CNT6 CNT5 CNT4 CNT3 CNT2 CNT1 CNT0
POR: 0 0 0 0 0 0 0 0
BIT 47 BIT 46 BIT 45 BIT 44 BIT 43 BIT 42 BIT 41 BIT 40
NAME: ACC47 ACC46 ACC45 ACC44 ACC43 ACC42 ACC41 ACC40
POR: 0 0 0 0 0 0 0 0
BIT 39 BIT 38 BIT 37 BIT 36 BIT 35 BIT 34 BIT 33 BIT 32
NAME: ACC39 ACC38 ACC37 ACC36 ACC35 ACC34 ACC33 ACC32
POR: 0 0 0 0 0 0 0 0
BIT 31 BIT 30 BIT 29 BIT 28 BIT 27 BIT 26 BIT 25 BIT 24
NAME: ACC31 ACC30 ACC29 ACC28 ACC27 ACC26 ACC25 ACC24
POR: 0 0 0 0 0 0 0 0
BIT 23 BIT 22 BIT 21 BIT 20 BIT 19 BIT 18 BIT 17 BIT 16
NAME: ACC23 ACC22 ACC21 ACC20 ACC19 ACC18 ACC17 ACC16
POR: 0 0 0 0 0 0 0 0
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8
NAME: ACC15 ACC14 ACC13 ACC12 ACC11 ACC10 ACC9 ACC8
POR: 0 0 0 0 0 0 0 0
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NAME: ACC7 ACC6 ACC5 ACC4 ACC3 ACC2 ACC1 ACC0
POR: 0 0 0 0 0 0 0 0
MAX34407 SMBus 4-Channel Wide Dynamic Range
Power Accumulator
www.maximintegrated.com
Maxim Integrated
│
13
Bits 47 to 0: ACC47 to ACC0
These bits report the total power accumulated by each channel. Send the UPDATE command before reading these reg-
isters. The power accumulators do not roll over. If any of the power accumulator overflows, the OVF bit in the CONTROL
command is set and remains set until the UPDATE command is sent.
Bits 15 to 4: V11 to V0
These bits report the last measured common-mode voltage for each channel. The LSB bit weighting is 3.9mV (16V full
scale/4096). The UPDATE command must be sent before reading the channel voltages. The host should wait 500µs after
sending the UPDATE command before reading the VOLTAGE commands.
Bits 7 to 3: ID4 to ID0
These bits report the device identification (ID). The ID is fixed at 05h.
Bits 2 to 0: REV2 to REV0
These bits report the device revision. The device revision is factory set.
Applications Information
Average Power Calculation Example
The average power can be derived in an external calculation as shown below if the current sense resistor value is known.
Power accumulator (48 bit) = 0001CEFBD314h (7767577364 decimal)
Accumulator counter (24 bit) = 0005DEh (1502 decimal)
Current-sense resistor = 10mΩ
Step 1
Calculate the unscaled average power by dividing the power accumulator value with the accumulator count value:
0001CEFBD314h/0005DEh = 4EE921h (5171489 decimal)
Step 2
Calculate the ratio of the Step 1 result to the calculated power full-scale value which is a 28-bit value:
5171489/2
28
= 0.019265
Table 10. Voltage for Channel 1 (07h)—Block Read
Voltage for Channel 2 (08h)—Block Read
Voltage for Channel 3 (09h)—Block Read
Voltage for Channel 4 (0Ah)—Block Read
Table 11. Device ID & Revision Register (0Fh)—Read Byte
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8
NAME: V11 V10 V9 V8 V7 V6 V5 V4
POR: 0 0 0 0 0 0 0 0
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NAME: V3 V2 V1 V0 N/A N/A N/A N/A
POR: 0 0 0 0 0 0 0 0
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
NAME:
ID4 ID3 ID2 ID1 ID0 REV2 REV1 REV0
POR:
0 0 1 0 1 Factory set
Note: Bit positions marked as N/A are not assigned and have no meaning. These bits can be either 0 or 1 when read.
MAX34407 SMBus 4-Channel Wide Dynamic Range
Power Accumulator
www.maximintegrated.com
Maxim Integrated
│
14
Step 3
Multiply the result from Step 2 by the correction factor listed in Table 12 that matches the current-sense resistor value:
0.019265 x 160 = 3.08W
Kelvin Sense
For best performance, a Kelvin sense arrangement is recommended. See Figure 2. In a Kelvin sense arrangement,
the voltage sensing nodes across the sense element are placed so that they measure the true voltage drop across
the sense element and not any additional excess voltage drop that can occur in the copper PCB traces or the solder
mounting of the sense element. Routing the differential sense lines along the same path to the MAX34407 and keeping
the path short also improve the system performance.
Minimizing Trace Resistance
PCB trace resistance from the sense resistor (RSENSE) to the IN+ inputs can affect the MAX34407 power measurement
accuracy. Every 1 ohm of PCB trace resistance will add about 25µV of error. It is recommended to place the sense resistors
as close as possible to the MAX34407 and not to use minimum width PCB traces.
Table 12. Correction Factors for Various Current-Sense Resistor Values
CURRENT-SENSE
RESISTOR VALUE
(mΩ)
FULL-SCALE
CURRENT
(A)
FULL-SCALE
VOLTAGE
(V)
POWER SCALE
CORRECTION
CALCULATION
POWER SCALE
CORRECTION FACTOR
(W)
100 1 16 1 x 16 16
50 2 16 2 x 16 32
40 2.5 16 2.5 x 16 40
25 4 16 4 x 16 64
20 5 16 5 x 16 80
15 6.667 16 6.667 x 16 106.667
10 10 16 10 x 16 160
5 20 16 20 x 16 320
4 25 16 25 x 16 400
2 50 16 50 x 16 800
1 100 16 100 x 16 1600
Figure 2. Kelvin Sense Connection Layout Example
CURRENT PATH
SENSE RESISTOR OUTLINE
ROUTE SENSE LINES ALONG
THE SAME PATH
COPPER
TRACE
COPPER
TRACE
IN+
IN-
KELVIN CONNECTIONS
MAX34407 SMBus 4-Channel Wide Dynamic Range
Power Accumulator
www.maximintegrated.com
Maxim Integrated
│
15
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17

MAX34407EWE+T

Mfr. #:
Buy MAX34407EWE+T
Manufacturer:
Maxim Integrated
Description:
Current & Power Monitors & Regulators SMBUS 4 CHANNEL WIDE DYNAMIC RANGE
Lifecycle:
New from this manufacturer.
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