rt9246a Richtek Technology Corporation, rt9246a Datasheet - Page 14

• Manufacturer Part Number: rt9246a
• Description: Multi-phase Controller Core Power Supply
• Manufacturer: Richtek Technology Corporation

RT9246A
Design Procedure Suggestion
a.Output filter pole and zero (Inductor, output capacitor
b.Error amplifier compensation & sawtooth wave amp-
Current Loop Setting
a.GM amplifier S/H current (current sense component
b.Over-current protection trip point (R
VRM Load Line Setting
a.Droop amplitude (ADJ pin resistor).
b.No load offset (R
c.DAC offset voltage setting (VOSS pin and compensation
Power Sequence & SS
DVD pin external resistor and SS pin capacitor.
PCB Layout
a.Sense for current sense GM amplifier input.
b.Refer to layout guide for other items.
Voltage Loop Setting
Design Example
Given:
Apply for four phase converter
V
V
I
V
OCP trip point set at 35A for each channel (S/H)
www.richtek.com
14
LOAD(MAX)
IN
CORE
DROOP
value & ESR).
litude (compensation network).
DCR, ISPX and ICOMMON pin external resistor value).
network resistor RB1)
= 12V
= 1.5V
= 100mV at full load (1mΩ Load Line)
= 100A
CSN
)
Figure 16.
Gain-Bandwidth Measurement by signal A divided by signal B
IMAX
resistor).
B
V
4.7k
REF
-
+
4.7k
EA
DCR = 1mΩ of inductor at 25°C
L = 1.5μH
C
1. Compensation Setting
a. Modulator Gain, Pole and Zero:
b. EA Compensation Network:
OUT
From the following formula:
Modulator Gain =V
where V
LC Filter Pole = 1.45kHz and
ESR Zero =3.98kHz
Select R1 = 4.7k, R2 = 15k, C1 = 12nF, C2 = 68pF
and use the Type 2 compensation scheme shown in
Figure 17. By calculation, the F
F
10.07dB).
P
Figure 17. Type 2 compensation network of EA
= 8000μF with 5mΩ equivalent ESR.
= 322kHz and Middle Band Gain is 3.19 (i.e
A
RAMP
: ramp amplitude of saw-tooth wave
RB1
4.7k
IN
/V
RAMP
RB2
15k
C2 68pF
+
-
EA
=12/1.9 = 6.3 (i.e 16dB)
DS9246A-04 March 2007
12nF
C1
Z
= 0.88kHz,