RT9644 RICHTEK [Richtek Technology Corporation], RT9644 Datasheet - Page 5

• Manufacturer Part Number: RT9644
• Description: ACPI Regulator/Controller for Dual Channel DDR Memory Systems
• Manufacturer: RICHTEK [Richtek Technology Corporation]

DS9644/A-01 August 2007
RT9644
14
15
16
17
18
19
20
21
Pin No.
RT9644A
14
15
16
18
20
21
--
--
VREF_IN
FB
COMP
FB4
FB3
DRIVE3
REFADJ4
DRIVE4
Pin Name
A capacitor, C
capacitor and the parallel combination of the Upper and Lower Divider
Impedance (RU//RL), sets the time constant for the start up ramp when
transitioning from S3/S4/S5 to S0/S1/S2. The soft start capacitance will
determine the V
FB is the error amplifier negative input that needs proper resistance divider
connected to V
control mode. It needs a typical Type 2 compensation network from COMP to
FB (or Type 3). The reference voltage of the error amplifier is 0.8V m onitored
by under and over voltage protection.
The COMP is the output to the voltage loop error amplifier. Loop
compensation is achieved by connecting an AC network across COMP and
FB.
In RT9644, the FB4 pin connects the output of the upper V
linear regulator to this pin. The voltage at this pin is regulated via the
REFADJ4 pin (Pin 20). Generally, the FB4 is connected to V
REFADJ4 = V
(V
equal to (V
In RT9644A, the FB4 is the 2
amplifier feedback. There should be the suitable AC compensation RC
network. The compensation may be Type 2 even Type 3. The feedback
voltage is monitored by the under voltage protection.
In RT9644, the FB3 pin connects the output of the lower V
linear regulator to this pin through a properly sized resistor divider. The
voltage at this pin is regulated to 0.8V. This pin is monitored for under-voltage
protection.
In RT9644A, the pin connects the output of the V
proper resister divider.
In RT9644, the DRIVE3 pin provides the gate voltage for the lower V
linear regulator pass transistor. Connect this pin to the gate terminal of an
external N-MOSFET transistor.
In RT9644A, the DRIVE3 pin provides the gate voltage for the V
regulator pass transistor. Connect this pin to the gate terminal of an external
N- MOSFET transistor.
This REFADJ4 pin controls the V
ENSURE that both upper and lower pass transistors dissipate the same
power, connecting this REFADJ4 pin to the V
The DRIVE4 pin provides the gate voltage for the upper V
linear regulator. Connect this pin to the gate terminal of an external
N-MOSFET transistor.
C
SS
DDQ
> (C
+REFADJ4)/2 as reference voltage. Then we can have the VGMCHH
VTT
DDQ
Preliminary
x V
GMCH
SS
+V
DDQ
TT_DDR
, connected between VREF_IN and ground is required. This
DDQ
GMCH
. The V
. The V
) / [10 x 2 x 1A x (RU//RL)]
)/2.
soft start ramp by the above RC time constant.
GMCHH
DDQ
nd
Pin Function
synchronous DC-DC buck is simple voltage
GMCHH
synchronous DC-DC buck converter error
LDO controller will set the positive input to
LDO controller reference voltage. To
GMCH
output rail.
DAC
RT9644/A
linear regulator with
GMCH
GMCH
To be continued
www.richtek.com
GMCH
GMCHH
DAC
(V
(V
(V
GMCHH
GMCHH
GMCH
, and
GMCH
linear
5
)
)
)