NCP5222 ON Semiconductor, NCP5222 Datasheet - Page 11

• Manufacturer Part Number: NCP5222
• Description: High Performance Dual-channel / Two-phase Synchronous Buck Controller For Notebook Power System
• Manufacturer: ON Semiconductor

Control Logic
(UVLO) function. If V
converter has a soft−start after EN signal goes high. The
internal digital soft−start time is fixed to 1 ms. The two
channels share one DAC ramping−up circuit. If the two ENs
become high at the same time (within 5 ms), the two channels
start soft−start together; If one channel’s EN comes when the
other channel is powering up, the channel starts powering up
after the other channel completes soft start. If one channel’s
EN comes when the other channel is in any fault condition,
the channel does not start powering up until the fault is
cleared. The NCP5222 has output discharge operation
through one internal 20 W MOSFET per channel connected
from CS−/Vo pin to PGND pin, when EN is low or the
channel is under any fault condition.
Current−Sense Network
sensed differentially. A high gain and low offset−voltage
PGOOD1
PGOOD2
EN2 goes high and
mode detection starts.
The NCP5222 monitors V
In the NCP5222, the output current of each channel is
DRVS
VCC
EN1
EN2
Vo1
Vo2
VIN
Mode detection
complete.
System and Ch2 reset complete
and Ch2 soft start begins.
3.5us
53us
67us
3 .6V
CC
4.2 5V
is in normal operation range, the
0 .5V
Ch2 r amping up
complet e.
1ms
CC
with undervoltage lockout
260 us
Figure 6. Timing Diagram in Two−Phase Mode
150us
Ch2 i n
regul ati on.
PGOOD2
vali d.
EN1 goes hi gh
and Ch1 reset.
57us
http://onsemi.com
Ch1 sof tst art
begins.
1ms
11
Ch1 rampi ng up
complet e.
differential amplifier in each channel allows low−resistance
current−sense resistor or low−DCR inductor to be used to
minimize power dissipation. For lossless inductor current
sensing as shown in Figure 7, the sensing RC network
should satisfy:
where the dividing−down ratio k
is selected to be around 0.1 mF. The current−sense input
voltage across CS+ and CS− is
by temperature, an additional resistance network including
0.2V
DCR
260us
DCR is a DC resistance of an inductor, and normally CCS
If there is a need to compensate measurement error caused
L
Ch1 i n
regul ation.
150us
+
R
R
PGOOD1 valid and
DRVS soft start begins.
CS1
CS1
) R
@ R
DRVS soft start
complet e.
k
V
CS2
CS2
CS
CS
+
+ k
@ C
R
CS
CS
CS1
Ch1 power down.
R
+ k
@ I
) R
CS2
CS
L
@ DCR
CS
is
CS2
@ R
CS1
@ C
Ch2 power down.
CS
(eq. 1)
(eq. 2)
(eq. 3)