NCP5422A_06 ONSEMI [ON Semiconductor], NCP5422A_06 Datasheet - Page 9

• Manufacturer Part Number: NCP5422A_06
• Description: Dual Out−of−Phase Synchronous Buck Controller with Current Limit
• Manufacturer: ONSEMI [ON Semiconductor]

Output Enable
implemented by pulling the COMP pins low. The COMP
pins must be driven below the 0.425 V PWM comparator
offset voltage in order to disable the switching of the GATE
drivers.
Definition of the design specifications
of the following reasons:
take into account all of the above effects and provide an
output voltage that will meet the specified tolerance at the
load.
component temperatures are kept within the manufacturer’s
specified ratings at full load and maximum ambient
temperature.
On/Off control of the regulator outputs can be
The output voltage tolerance can be affected by any or all
Budgeting the tolerance is left up to the designer who must
The designer must also ensure that the regulator
1. buck regulator output voltage setpoint accuracy;
2. output voltage change due to discharging or charging
3. output voltage change due to the ESR and ESL of the
4. output voltage ripple and noise.
of the bulk decoupling capacitors during a load
current transient;
bulk and high frequency decoupling capacitors,
circuit traces, and vias;
Figure 6. Hiccup Overcurrent Protection
DESIGN GUIDELINES
NCP5422A, NCP5423
http://onsemi.com
9
Selecting Feedback Divider Resistors
Selection of Feedback Divider Resistors
on a design trade−off between efficiency and output voltage
accuracy. Both error amplifiers are referenced to 1.0 V, and
resistors R1 and R2 are connected from each channel’s
output voltage to the inverting pin (V
amplifier. To set the channel output voltage, first choose a
value for R1, and then R2 can be sized as follows:
amplifier and the parallel combination of R1 and R2 can now
be estimated:
voltage error, but increase the power dissipation.
Calculating Duty Cycle
losses) is given by the formula:
where:
Feedback divider resistors R1 and R2 are selected based
The output voltage error due to the bias current of the error
Reducing the size of R1 and R2 will reduce the output
The duty cycle of a buck converter (including parasitic
Figure 7. Selecting Feedback Divider Resistors
V
V
V
V
V
OUT
HFET
L
IN
LFET
Duty Cycle + D +
= output inductor voltage drop due to inductor wire
= buck regulator input voltage;
DC resistance;
= buck regulator output voltage;
= low side FET voltage drop due to R
= high side FET voltage drop due to R
Error + 1.6 · 10 −6 · R1 · R2
V
R2 +
OUT
R1
R2
V IN ) V LFET * V HFET
V OUT ) V LFET ) V L
Vout
1.0
R1
* 1
V
FB
R1 ) R2
FB1(2)
) of each error
DS(ON)
DS(ON)
.
;