RT9911PQV RICHTEK [Richtek Technology Corporation], RT9911PQV Datasheet - Page 24

• Manufacturer Part Number: RT9911PQV
• Description: 6 Channel DC/DC Converters
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9911
RT9911 Component Selection for Compensation :
CH1 Sync-Boost (Select Pin = High Logic) :
CH1 sync-boost converter employs current-mode control
to simplify the control loop compensation. There is a RHPZ
(Right Hand Plane Zero) appeared in the loop-gain
frequency response when a boost converter operates with
continuous inductor current (typically the case), we also
call it works in CCM (Continuous Current Mode). For
stability, cross over frequency (f
must lower than this RHPZ frequency.
The fixed parameters for CH1 boost compensation are as
follows :
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24
COMP
Transconductance (from FB to COMP), GM = 200us
Current sense transresistance, R
Feedback voltage, V
Figure 6. CH3 Current Limit Setting
C
P
R
C
PWM
CH3
C
C
GM
10uA
+
-
FB
FB
V
Figure 7
0.8V
DDM
DRN3
= FB = 0.8V
CS3
V
OUT
R1
R2
C
), unity gain frequency,
V
BAT
CS
C
F
LX3
= 0.4V/A
I
inductor
R
C
ESR
OUT
I
OUT
The input parameters for CH1 boost compensation are as
follows:
The results we will get for CH1 boost compensation are
as follows:
R1, the voltage divider resistor in between V
FB.
V
V
I
F
L, inductance
R
(ceramic output capacitor)
T
R2, the voltage divider resistor in between FB and ground.
C
R
C
connect to ground.
C
ignored if C
C
on ceramic output capacitor.
WLED
OUT(MAX.)
OSC
DRP
IN
OUT
F
C
P
OUT
ESR
C
,
, compensation resistor on COMP pin.
, connect in between COMP pin and ground. (Can be
, compensation capacitor in series with Rc and
Figure 8. CH6 Over Voltage Protection Method
, input voltage.
feedforward capacitor in parallel with R1.
(V
(%), Transient droop.
, desired output voltage
, operating frequency
, ESR (Equivalent Series Resistance) of C
, output capacitance. This compensation is based
WLED
, maximum output load
P
> 50μA x R+1V, protection happens)
< 10pF).
R
V
BAT
VFB6
EXT6
DS9911-04 August 2007
50uA
1V
CFB6
-
+
OUT
PWM
CH6
and
OUT