MAX16046A Datasheet, PDF (60/71 Pages) Maxim Integrated Products – 12-Channel/8-Channel EEPROM-Programmable System Managers with Nonvolatile Fault Registers

12-Channel/8-Channel EEPROM-Programmable
System Managers with Nonvolatile Fault Registers
DC-DC OR LDO
OUT
FB
R₁
R₃
R₂
V_REF
MAX16046A
MAX16048A
V_{DACOUT_}
DC-DC OR LDO
OUT
R₁
FB
R_3A
R₂
V_REF
R_3B
C
MAX16046A
MAX16048A
V_{DACOUT_}
Figure 15. Connections for Margining Using Feedback Method
Filtering the DAC Outputs
Some applications require filtering of the DAC outputs.
This is especially necessary in applications that require
a large distance between the power supplies to be
margined and the MAX16046A/MAX16048A, or those
that require immunity to noise. A simple RC filter may
be inserted (see Figure 16).
The calculations change slightly for this configuration.
For DC margining calculations, R₃ = R_3A + R_3B. To cal-
culate the lowpass cutoff frequency, use the following
formula:
f= ¹
2πR _3BC
Place resistor R_3A and the capacitor, C, as close as
possible to the feedback node.
Trim Input Method
To connect the MAX16046A/MAX16048A to a power
supply using the trim input method, see Figure 17.
Calculate the output voltage, V_OUT, as follows:
V_OUT
=
⎛
⎝⎜ ^{1 +}
R₁
R₂
⎞⎛
⎠⎟ ⎝⎜
R₃V_{DACOUT_} + (R₄ + R ₅)V_REF
R₃ + R₄ + R₅
⎞
⎠⎟
where V_REF is the reference voltage of the power sup-
ply; R₁, R₂, R₃, and R₄ are resistors internal to the
power supply; R₅ is an optional series resistor connect-
ing the trim input to the DACOUT_ output; and
V_{DACOUT_} is the output voltage of the DACOUT_ output.
Figure 16. DACOUT Filter
Calculate the ratio of R₁ and R₂ using the following for-
mula:
⎛
⎝⎜ ^{1 +}
R₁
R₂
⎞
⎠⎟
=
V_{OUT_NOM}
V_REF
Resistors R₃ and R₄ and the reference voltage V_REF
may be derived from the formulas given in the DC-DC
converter data sheet where trim input functionality is
discussed. DC-DC module data sheets usually include
trim-up and trim-down formulas in the following form:
TRIM
DOWN:R
ADJ_DOWN
(kΩ)
=
⎛
⎝⎜
1
−Δ
Δ
⎞
⎠⎟
R₃
(kΩ)
−
R₄
(kΩ)
TRIM
UP:R _{ADJ_UP} (kΩ)
=
⎛
⎝⎜
V_{OUT_NOM}
V_REF
⎞
− 1_⎠⎟
⎛
⎝⎜
1− Δ
Δ
⎞
⎠⎟
R₃
(
kΩ
)
− R₄ (kΩ)
where Δ is the fraction of the total correction.
Another form of trim-up and trim-down formulas may
appear as follows:
( ) ^TRIM
DOWN:R _{ADJ_DOWN} (kΩ)
=
⎛
⎜
⎝
R₃
(kΩ) × 100
Δ%
−
R₄ (kΩ) + R₃ (kΩ)
⎞
⎟
⎠
( ) _TRIM
UP:R _{ADJ_UP}
(kΩ)
=
⎛
⎜
⎝⎜
V_{OUT_NOM}
R₃ (kΩ) × (100 + Δ%)
V_REF Δ%
⎞
⎟
⎠⎟
( ) _−
⎛
⎜
R
3
(
kΩ
)
×
100
+
R₄ (kΩ) + R₃ (kΩ)
Δ% ^⎞
⎟
⎝⎜
Δ%
⎠⎟
60 ______________________________________________________________________________________