MAX16928EVKIT# Maxim Integrated, MAX16928EVKIT# Datasheet - Page 16

• Manufacturer Part Number: MAX16928EVKIT#
• Description: Power Management IC Development Tools Eval Kit MAX16928 (Complete Automotive TFT-LCD Display Power Supply)
• Manufacturer: Maxim Integrated
• Series: MAX16928r

4) Next, calculate the pole set by the regulator’s feed-
5) Next, calculate the zero caused by the output capaci-
Table 3
tance for the negative-gate voltage regulator and is appli-
cable for output currents in the 10mA to 15mA range.
Maxim Integrated
found in the transistor’s data sheet. Because R
much greater than R
simplified:
Substituting for C
back resistance and the capacitance between FBGL
and GND (including stray capacitance):
where C
GND and is equal to 30pF, R
of the regulator’s feedback divider, and R
the lower resistor of the divider.
tor’s ESR:
where R
C
enough so the crossover occurs well before the poles
and zero calculated in steps 2 to 5. The poles in steps
3 and 4 generally occur at several MHz and using
ceramic capacitors ensures the ESR zero also occurs
at several MHz. Placing the crossover frequency
below 500kHz is sufficient to avoid the amplifier delay
pole and generally works well, unless unusual compo-
nent choices or extra capacitances move one of the
other poles or the zero below 1MHz.
OUT_LR
f
POLE_FBGL
is a list of recommended minimum output capaci-
Automotive TFT-LCD Power Supply with Boost
f
ZERO_ESR
FBGL
ESR
. To ensure stability, make C
f
POLE_IN
is the equivalent series resistance of
is the capacitance between FBGL and
=
2
IN
π ×
f
=
POLE
and R
C
2
IN
=
π ×
FBGL
, the above equation can be
Converter and Gate Voltage Regulators
2
π ×
=
C
IN
h
OUT_LR
C
f
×
FE
yields:
T
TOP
IN
1
(R
1
1
×
TOP
is the upper resistor
R
IN
×
/R
R
ESR
BOTTOM
OUT_LR
BOTTOM
)
BE
large
is
is
Table 3. Minimum Output Capacitance vs.
Output Voltage Range for Negative-Gate
Voltage Regulator (I
An IC’s maximum power dissipation depends on the ther-
mal resistance from the die to the ambient environment
and the ambient temperature. The thermal resistance
depends on the IC package, PCB copper area, other
thermal mass, and airflow. More PCB copper, cooler
ambient air, and more airflow increase the possible dis-
sipation, while less copper or warmer air decreases the
IC’s dissipation capability. The major components of
power dissipation are the power dissipated in the boost
converter, positive-gate voltage regulator, negative-gate
voltage regulator, and the 1.8V/3.3V regulator controller.
Power dissipation in the boost converter is primarily due
to conduction and switching losses in the low-side FET.
Conduction loss is produced by the inductor current
flowing through the on-resistance of the FET during the
on-time. Switching loss occurs during switching transi-
tions and is a result of the finite time needed to fully turn
on and off the FET. Power dissipation in the boost con-
verter can be estimated with the following formula:
where I
input (i.e., inductor) current, D is the duty cycle of the
boost converter, R
the internal low-side FET, V
f
R
SW
DS_ON(LXP)
P
LXP
is the switching frequency of the boost converter.
I
OUTPUT VOLTAGE
IN(DC,MAX)
-8V R V
-2V R V
-5V R V
≈ [(I
IN(DC,MAX)
RANGE
IN(DC,MAX)
GL
GL
GL
is 110mI (typ) and f
R -13V
R -4V
R -7V
Applications Information
× f
SW
DS_ON(LXP)
is the maximum expected average
×
× [(t
√
D)
OUT
R-V
SH
2
× R
is the output voltage, and
+ t
MAX16928
is the on-resistance of
= 10mA to 15mA)
CAPACITANCE (µF)
Power Dissipation
MINIMUM OUTPUT
DS_ON(LXP)
F-I
SW
) + (t
is 2.2MHz.
Boost Converter
2.2
1.5
R-I
1
+ t
] + V
F-V
SH
)]
×
16