MAX5971B Maxim Integrated Products, MAX5971B Datasheet - Page 38

• Manufacturer Part Number: MAX5971B
• Description: PSE Controller
• Manufacturer: Maxim Integrated Products

Table 34. PWM Duty-Cycle Settings
Single-Port, 40W, IEEE 802.3af/at,
PSE Controller with I
mode. When DET_BY is set to 1 however, the MAX5971B
can power the port without doing the detection routine.
AC_TH[2:0] (R23h[2:0]) allows direct programming of
the AC disconnect threshold. The threshold is defined
as a current since the comparator verifies that the peak
current pulses sensed at the DET input exceeds a preset
threshold. The current threshold is defined as follows:
Table 33. PWM Register
38
SYMBOL
Reserved
Reserved
Reserved
PWM_TH
_____________________________________________________________________________________
I
ADDRESS = 24h
AC_TH
BIT NO.
= 85.28FA + 10.64FA x N
7
6
5
4
3
2
1
0
PWM_TH[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
—
—
00
01
10
11
Reserved
Reserved
PWM_TH[1]
PWM_TH[0]
Internally connected. For a write command, always write a zero to this bit.
AC_TH
2
C
where N
default N
sponds to a default I
The PWM register (R24h, Table 33) is used to program
the PWM duty cycle. On a power-up or after a reset
condition, this register is set to a default value of 0x00h.
PWM_TH[1:0] (R24h[5:4]) is used to set the PWM duty
cycle. The default PWM_TH[1:0] value of 00 corresponds
to a 6.25% duty cycle, while the maximum PWM_TH[1:0]
value of 11 corresponds to a 25% duty cycle (see Table 34).
DESCRIPTION
AC_TH
AC_TH
is the decimal value of AC_TH[2:0]. The
is 4 (AC_TH[2:0] = 100) which corre-
DUTY CYCLE (%)
AC_TH
18.75
6.25
12.5
25.0
of ~128FA.
PWM Register (R24h)