NCP5212A_09 ONSEMI [ON Semiconductor], NCP5212A_09 Datasheet - Page 13

• Manufacturer Part Number: NCP5212A_09
• Description: Single Synchronous Step-Down Controller
• Manufacturer: ONSEMI [ON Semiconductor]

large enough to exceed the threshold and then TRE “flag”
signal will be asserted in a short period which is typically
around one normal switching cycle. In this short period, the
controller will be running at high frequency and hence has
faster response. After that the controller comes back to
normal switching frequency operation. We can program the
internal TRE threshold (TRE_TH). For detail please see the
electrical table of “TRE Setting” section. Basically, the
recommend internal TRE threshold value is around 1.5
times of peak−to−peak value of the COMP signal at CCM
operation. The higher the internal TRE_TH, the lower
sensitivity to load transient. The TRE function can be
disable by setting the Rtre which is connecting to DL/TRE
pin to less than 25 kW. For system component saving, it is
usually set as default value, that is, Rtre is open (w75 kW)
and internal TRE_TH is 300 mV typical.
Once the large transient occurs, the COMP signal may be
Figure 18. Transient Response with TRE Disable
Figure 19. Transient Response with TRE Enable
Top to Bottom SWN, Vo, Transient Signal
Top to Bottom SWN, Vo, Transient Signal
http://onsemi.com
13
Adaptive Voltage Positioning (AVP)
voltage positioning can reduce peak−to−peak output voltage
deviations due to load transients. With the use of AVP, the
output voltage allows to have some controlled sag when load
current is applied. Upon removal of the load, the output
voltage returns no higher than the original level, just
allowing one output transient peak to be cancelled over a
load step up and release cycle. The amount of AVP is
adjustable.
are depicted at Figure 20.
current path is connecting to the FB pin via Rocp resistor.
Rocp is not actually for AVP function, indeed, Rocp is used
for OCP threshold value programming. The IDRP/OCP pin
has dual functions: OCP programming and AVP. At the
IDRP/OCP pin, conceptually there is a current source which
is modulated by current sensing amplifier.
The output voltage V
Where I
set by the external divider that is:
For applications with fast transient currents, adaptive
The behaviors of the V
The Figure 21 shows how to realize the AVP function. A
Figure 21. Configuration for AVP Function
Figure 20. Adaptive Voltage Positioning
o
Vo
L
DCR
Vo With AVP
Vo Without AVP
is the load current, no load output voltage V
Rb
Rt
Rs1
Cs
IDRP/OCP
V
Rocp
V
Rs2
O
O
0 + 1 )
o
CS+
CS−
FB
+ V
with AVP is:
o
waveforms with or without AVP
O
0 * I
+
−
Vref
+
+
Rb
Rt
G i
O
* R
* V
LL
I DRP
ref
COMP
(eq. 1)
(eq. 2)
o
0 is