ncp5215 ON Semiconductor, ncp5215 Datasheet - Page 15

• Manufacturer Part Number: ncp5215
• Description: Dual Synchronous Buck Controller For Notebook
• Manufacturer: ON Semiconductor

applications, to compensate measurement error caused by
temperature, an additional resistance network including a
negative-temperature-coef ficient (NTC) thermistor can
be connected with C
where I
by the external resistor divider, that is
R
pin, and R
AGND. The load-line impedance R
is given by
where DCR is DC resistance of the inductor, Gain_CS is a
gain from [(CS+)-(CS-)] to (VDRP-VREF), R
internal resistance connected between the output reference
and the VDRP Pin, R
connected between the output reference and the VDRP pin.
Figure 31. Programmable AVP with Lossless Inductor
V
V
FO
R
The output voltage with AVP is
O
O0
LL
is a resistor connected between the output and the FB
Figure 32. Figure 32. Programmable AVP with
+ V
+ DCR Gain_CS @
+ 1 )
o
is load current, no-load output voltage V
O0
FG
* I
is a resistor connected between the FB Pin to
Resistive Current Sensing
R
R
O
FO
FG
@ R
Current Sensing
CS
LL
@ V
in parallel.
DRP_ext
REF
R
DRP_int
R
DRP_ext
is a external resistance
) R
LL
by the AVP function
DRP_ext
@
DRP_int
V
V
REF
O0
O0
http://onsemi.com
(eq. 3)
(eq. 4)
(eq. 5)
is set
is a
NCP5215
15
If an additional current sensing resistor (R
to improve accuracy, as shown in Figure 32, the load line
resistance can be calculated by
VDRP pin and VREF pin together.
Control Logic
shows a power-up and powerdown timing diagram for
each channel. Figure 34 shows a state diagram for each
channel.
with an undervoltage lockout (UVLO) function. If both
V
below 0.3 V, the converter has a soft-start after ENBL
signal goes high. The soft-start time is programmed by an
external capacitor C
AGND, which can be calculated by
where I
by over current or output undervoltage, the device operates
in soft stop and output discharge mode. The output is
discharged to GND through an internal 12 W switch
connected from the CS-/Vo pin to the PGND Pin, until the
output voltage decreases to 0.3 V. Also if restart the system
when the output voltage is still above 0.3 V, the device will
discharge the output voltage to 0.3 V first and then start
soft-start.
Overcurrent Protection (OCP)
occurs. The current through each channel is continuously
monitored with the differential current sense. Current limit
threshold is related to an external voltage at the I
which is normally produced by an external resistor divider
(R
current-limit threshold for peak current is set by
or
continuously, the top gate drive will be turned off
cycle-by-cycle. In the meanwhile, an internal fault timer
will be triggered to count normal operation clock. After 16
continuous clock pulses, if the fault still exists the part
latches off, both the top gate drive and the bottom gate drive
R
t
I
I
CC
The AVP function can be easily disabled by shorting
The internal control logic is powered by V
The NCP5215 continuously monitors V
When the ENBL goes low, or the internal fault latch is set
The NCP5215 protects power system if overcurrent
If inductor current exceeds the current threshold
SS
LIM(Peak)
LIM(Peak)
il1
LL
and V
and R
+
+ R
SS
0.8
CS
is a sourcing current output from the SS pin.
il2
IN
+ 0.2 @
+ 0.2 @
I
SS
) connected from the V
Gain_CS @
are in operation range, and output voltage is
C
SS
R
R
il1
il1
SS
R
R
) R
) R
il2
R
il2
connected from the SS Pin to
DRP_int
@ V
@ V
il2
il2
REF
REF
R
@ DCR
@ R
DRP_ext
) R
CS
REF
DRP_ext
pin to AGND. The
CC
CS
) is employed
CC
and V
@
V
V
. Figure 33
REF
O0
LIM
IN
(eq. 6)
(eq. 7)
(eq. 8)
(eq. 9)
level
pin,