NCP5331_05 ONSEMI [ON Semiconductor], NCP5331_05 Datasheet - Page 31

• Manufacturer Part Number: NCP5331_05
• Description: Two-Phase PWM Controller with Integrated Gate Drivers
• Manufacturer: ONSEMI [ON Semiconductor]

the inductor’s resistance increase due to current heating and
ambient temperature rise. Also, depending on the current
sense points, the circuit board may add additional resistance.
In general, the temperature coefficient of copper is +0.393%
per C. If using a current sense resistor (R
pin voltage should be set based on the maximum value of the
sense resistor. To set the level of the I
where
current sense time constant (RC) should be slightly larger
than the RL time constant. If the RC time constant is too fast,
during step load changes the sensed current waveform will
appear larger than the actual inductor current and will
probably trip the current limit at a lower level than expected.
10. Overcurrent Timer
allow hiccup mode operation. Given the capacitance from
the C
can be calculated from the following equation.
t OVC + C OVC @ (OVC THRESH * OVC MIN ) I OVC
where
11. Soft Start Time
where
V COMP + V CORE @ 0 A ) Channel_Startup_Offset
Int_Ramp + 125 mV @ D 0.50
Ext_Ramp + D @ (V IN * V CORE ) (R CSx @ C CSx @ f SW )
For the overcurrent protection to work properly, the
The overcurrent timer sets the time the converter will
The Soft Start time (t
t SS + (V COMP * R C1 @ I COMP ) @ C C2 I COMP
I
DI
R
G
OVC
OVC
I
I
Int_Ramp
Ext_Ramp
OUT,LIM
OVC
OVC
COMP
+ C OVC @ (3.0 V * 0.25 V) 5.0 mA
+ C OVC @ 5.5
ILIM
Lo
V ILIM + (I OUT,LIM ) DI Lo 2) @ R @ G ILIM
/2
THRESH
MIN
pin to GND, the nominal overcurrent time (t
) Int_Ramp ) G CSA @ Ext_Ramp 2
is the current limit threshold of the converter,
is half the inductor ripple current,
is either (R
is the current sense to I
is the peak−to−peak external
is the overcurrent timer’s shutdown
voltage, nominally 3 V,
is the overcurrent timer’s starting
voltage, nominally 0.25 V,
is the charge current supplied to the
capacitor at the C
5 mA.
is the COMP source current from the
data sheet,
is the internal ramp value at the
corresponding duty cycle,
steady−state ramp at 0 A,
SS
10 5
) can be calculated from
LMAX
+ R
PCB
OVC
LIM
LIM
) or R
pin,
pin, nominally
SENSE
gain.
SENSE
), the I
http://onsemi.com
,
OVC
(34)
(35)
(36)
LIM
NCP5331
)
31
12. Power Good Delay Time
V
and when PGD will actually transition high. The PGD delay
time can be calculated from
t PGD + C PGD @ (PGD THRESH * PGD MIN ) I PGD
where
Typical Design Requirements:
1. Output Capacitor Selection
as the Rubycon 16MBZ1000M10X16: 16 V, 1000 mF,
2.55 A
number of output capacitors.
N OUT,MIN + ESR per capacitor @
CORE
The power good timer sets the delay time between when
V
V
V
VID Range: 0.800 Vdc − 1.550 Vdc
I
I
dI
f
T
T
t
t
t
DV
DV
DV
First, choose a low−cost, low−ESR output capacitor such
SS
OVC
PGD
O,MAX
OUT,LIM
SW
A,MAX
J,MAX
IN
CORE
OUT,RIPPLE
IN
G
Startup Offset is typically 0.60V.
PGD
PGD
I
= 80% min at full−load
−25 mV from VID setting = 1.225 Vdc
–37 mV from VID setting = 1.163 Vdc
−50 mV from VID setting = 1.150 Vdc
PGD
= 6.0 ms (Soft Start time)
CORE
CORE
CORE
+ C PGD @ (3.0 V * 0.25V) I PGD
CSA
/dt = 0.50 A/ms max
= 200 kHz
= 12.0 Vdc
RMS
= 6.0 ms (PGD Delay time)
= 120 ms (Overcurrent time)
exceeds the C
THRESH
MIN
= 1.20 Vdc (nominal)
= 52 A at full−load
= 120 C
= 55 C
, 19 mW, 10
at no−load (static) =
at full−load (static) =
transient loading from 3.0 A to 25 A =
= 72 Adc
+ 19 mW @ 22 A (1.225 V * 1.150 V)
+ 5.6 or 6 capacitors minimum (6000 mF)
< 20 mV
is the Current Sense Amplifier Gain
(nominally 2.0 V/V),
is the PGD comparator’s threshold
voltage, nominally 3 V,
is the PGD timer’s starting voltage,
nominally 0.25 V,
is the charge current supplied to the
capacitor at the C
is a function of the R
according to I
Design Example
PGD
PP
16 mm. Calculate the minimum
comparator’s threshold voltage
max
PGD
DV O,MAX
DI O,MAX
PGD
= 0.52 V/R
OSC
pin. This current
resistor
OSC
.
(37)
(1)