ISL6115CBZA-T Datasheet, PDF (7/13 Pages) Intersil Corporation – Power Distribution Controllers

ISL6115, ISL6116, ISL6117, ISL6120
R_CL
1.58kΩ
1W
LOAD
0.001µF
2kΩ
0.005
1%
1.47kΩ
1%
0.01µF
ISL6116
DD1
12V
0.047µF
NC
PWRON
V_{BUS -48V}
FIGURE 2. TYPICAL 5A LOAD CONTROL
Biasing the ISL6116
Table 3 gives typical component values for biasing the
ISL6116 in a ±48V application. The formulas and
calculations deriving these values are also shown in the
following equations.
TABLE 3. TYPICAL VALUES FOR A -48V HOT SWAP
APPLICATION
SYMBOL
PARAMETER
R_CL
DD1
1.58kΩ, 1W
12V Zener Diode, 50mA Reverse Current
When using the ISL6116 to control -48V, a Zener diode
may be used to provide the +12V bias to the chip. If a
Zener is used then a current limit resistor should also
be used. Several items must be taken into account
when choosing values for the current limit resistor
(R_CL) and Zener Diode (DD1):
• The variation of the V_BUS (in this case, -48V
nominal)
• The chip supply current needs for all functional
conditions
• The power rating of R_CL.
• The current rating of DD1
Formulas
Sizing R_CL is expressed in Equation 1:
R_CL
=
V_{-----B----U----S----(--M-----I--N----)---–----}1_----2_-
I_CHIP
(EQ. 1)
Power Rating of R_CL is expressed in Equation 2:
P_RCL = I_C(V_BUS(MAX) – 12)
(EQ. 2)
DD1 current rating is expressed in Equation 3:
I_DD1
=
(_---V_{----B----U----S----(--M-----A----X----)---–-----}1_---2_----)
R_CL
(EQ. 3)
Example:
A typical -48V supply may vary from -36 to -72V.
Therefore:
V_BUS,MAX = -72V
V_BUS,MIN = -36V
I_CHIP = 15mA (Max)
Sizing R_CL is expressed in Equation 4:
R_CL
=
-⁽--^V----^B----^U----^S----⁽--^M-----^I--^N----⁾---–-----¹---²----⁾
I_C
R_CL
=
3_----6_{-----–----}1_---2_--
0.015
R_CL = 16kΩ[TypicalValue = 1.58kΩ]
(EQ. 4)
Power rating of R_CL is expressed in Equation 5:
P_RCL = I_C(V_BUS(MAX) – 12)
P_RCL = (0.015)(72 – 12)
P_RCL = 0.9W[TypicalValue = 1W]
(EQ. 5)
DD1 current rating is expressed in Equation 6:
I_DD1
=
(_---V_{----B----U----S----(--M-----A----X----)---–-----}1_---2_----)
R_CL
I_DD1 = -⁽--₁₇---_.2--₅---₈^–----_k-¹--_Ω-²----⁾
(EQ. 6)
I_DD1 = 38mA[TypicalValue = 12Vrating, 50mA reverse current]
7
FN9100.7
April 29, 2010