MAX5978ETJ+ Maxim Integrated Products, MAX5978ETJ+ Datasheet - Page 17

• Manufacturer Part Number: MAX5978ETJ+
• Description: Hot Swap & Power Distribution 0-16V HOTSWAP CONTLR W/10BIT CUR VOLT MON
• Manufacturer: Maxim Integrated Products

Specifications of MAX5978ETJ+

• Product: Controllers & Switches
• Supply Voltage (max): 16 V
• Supply Voltage (min): 0 V
• Power Dissipation: 2759 mW
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Supply Current: 2.5 mA
• Package / Case: TQFN-32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 4a. ifast2slow Register Format
Table 4b. Setting Fast-Trip to Slow-Trip Threshold Ratio
To select and set the device slow-trip and fast-trip com-
parator thresholds, use the following procedure:
1) Select one of four ratios between the fast-trip thresh-
2) Determine the slow-trip threshold V
3) Calculate the necessary fast-trip threshold V
4) Select one of the three maximum current-sense
Description:
Resister Title:
Register Address:
old and the slow-trip threshold: 200%, 175%, 150%,
or 125%. A system that experiences brief but large
transient load currents should use a higher ratio,
whereas a system that operates continuously at high-
er average load currents might benefit from a smaller
ratio to ensure adequate protection. The ratio is set by
writing to the ifast2slow register. (The default setting
on power-up is 200%.)
anticipated maximum continuous load current during
normal operation, and the value of the current-sense
resistor. The slow-trip threshold should include some
margin (possibly 20%) above the maximum load cur-
rent to prevent spurious circuit-breaker shutdown and
to accommodate passive component tolerances:
based on the ratio set in step 1:
ranges: 25mV, 50mV, or 100mV. The current-sense
Bit 7
—
R
Current, Voltage Monitor, and 4 LED Drivers
V
Setting Circuit-Breaker Thresholds
TH,ST
FS1
V
0
0
1
1
TH,FT
0 to 16V, Hot-Swap Controller with 10-Bit
= R
Bit 6
—
= V
R
SENSE
TH,ST
x I
Current threshold fast-to-slow setting bits
ifast2slow
0x30
x (ifast2slow ratio)
Bit 5
LOAD,MAX
—
R
TH,ST
FS0
0
1
0
1
x 120%
Bit 4
—
R
based on the
TH,FT
Unused
R/W
Bit 3
5) Program the fast-trip and slow-trip thresholds by writ-
The device provides a great deal of system flexibil-
ity because the current-sense range, DAC setting, and
threshold ratio can be changed “on the fly” for systems
that must protect a wide range of interchangeable
load devices, or for systems that control the allocation
of power to smart loads. Table 5 shows the specified
ranges for the fast-trip and slow-trip thresholds for all
combinations of current-sense range and threshold ratio.
When an overcurrent event causes the device to shut
down the power channel, the open-drain FAULT output
alerts the system. Figure 2 shows the operation and fault-
management flowchart.
range is initially set upon power-up by the state of the
IRNG input, but can be altered at any time by writ-
ing to the status2 register. For maximum accuracy
and best measurement resolution, select the lowest
current-sense range that is larger than the V
value calculated in step 3.
ing an 8-bit value to the dac_fast register. This 8-bit
value is determined from the desired V
that was calculated in step 2, the threshold ratio from
step 1, and the current-sense range from step 4:
Unused
Bit 2
R/W
FAST-TRIP TO SLOW-TRIP RATIO (%)
DAC = V
(IRNG current-sense range)
TH,ST
Bit 1
R/W
FS1
125
150
175
200
x 255 x (ifast2slow ratio)/
R/W
Bit 0
FS0
TH,ST
RESET
VALUE
0x0F
—
TH,FT
value
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