RT8207LZQW datasheet(22/27 Pages) RICHTEK

22 / 27 page

DS8207L/M-08 September 2016

www.richtek.com

RT8207L/M

is a registered trademark of Richtek Technology Corporation.

Table 2. S3 and S5 truth table

STATE S3

VDDQ

VTTREF

VTT

Off (Hi-Z)

S4/S5 Lo

Off

(Discharge)

Off

(Discharge)

Off

(Discharge)

VDDQ and VTT Discharge Control

The RT8207L/M discharges VDDQ, VTTREF and VTT

outputs when S5 is low or in the S4/S5 state. There are

two different discharge modes. For the RT8207L, the

discharge mode is set by connecting the MODE pin

according to Table 3. For the RT8207M, the discharge

mode is set by placing a resistor (RTON) between the TON

pin and VIN, as shown in Table 4.

MODE

Discharge Mode

VDD

No discharge

VDDQ

Tracking discharge

GND

Non-tracking discharge

Table 3. Discharge selection for the RT8207L

TON pin connect RTON to

Discharge Mode

VIN

Non-tracking discharge

Table 4. Discharge selection for the RT8207M

When in tracking discharge mode, the RT8207L

discharges outputs through the internal VTT regulator

transistors and VTT output tracks half of the VDDQ voltage

during this discharge. Note that the VDDQ discharge

current flows via VLDOIN to VTTGND; thus VLDOIN must

be connected to VDDQ in this mode. The internal LDO

can handle up to 1.5A and discharge quickly. After VDDQ

is discharged down to 0.15V, the terminal LDO will be

turned off and the operation mode is changed to the non-

tracking discharge mode.

When in non-tracking discharge mode, the RT8207L/M

discharges outputs using internal MOSFETs which are

connected to VDDQ and VTT. The current capability of

these MOSFETs is limited to discharge slowly. Note that

the VDDQ discharge current flows from VDDQ to GND in

this mode.

When in no discharge mode, the RT8207L does not

discharge output charge at all.

Output Inductor Selection

The switching frequency (on-time) and operating point (%

ripple or LIR) determine the inductor value as follows :



 ON

VDDQ

LOAD(MAX)

x (V

)

x I

where LIR is the ratio of the peak-to-peak ripple current to

the maximum average inductor current.

Find a low loss inductor having the lowest possible DC

resistance that fits in the allotted dimensions. Ferrite cores

are often the best choice, although powdered iron is

inexpensive and can work well at 200kHz. The core must

be large enough not to saturate at the peak inductor current

(IPEAK) :



 

PEAK

LOAD(MAX)

(L /2) x I

Output Management by S3, S5 Control

In DDR2/DDR3 memory applications, it is important to

always keep VDDQ higher than VTT/VTTREF, even during

start up and shutdown. The RT8207L/M provides this

management by simply connecting both S3 and S5

terminals to the sleep-mode signals such as SLP_S3 and

SLP_S5 in notebook PC system. All VDDQ, VTTREF and

VTT are turned on at S0 state (S3 = S5 = high). In S3

state (S3 = low, S5 = high), VDDQ and VTTREF voltages

are kept on while VTT is turned off and left at high

impedance (high-Z) state. The VTT output is floated and

does not sink or source current in this state. In S4/S5

states (S3 = S5 = low), all of the three outputs are

disabled. Outputs are discharged to ground according to

the discharge mode selected by the MODE pin (see VDDQ

and VTT Discharge Control section). The code of each

state represents the following: S0 = full ON, S3 = suspend

to RAM (STR), S4 = suspend to disk (STD), S5 = soft

OFF. (See Table 2)

RT8207LZQW Datasheet(PDF) 22 Page - Richtek Technology Corporation

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