RT8167A datasheet(29/40 Pages) RICHTEK

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RT8167A

DS8167A-00

January 2012

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

ICCMAX, ICCMAXA and TMPMAX

The RT8167A provides ICCMAX, ICCMAXA and TMPMAX

pins for platform users to set the maximum level of output

current or VR temperature: ICCMAX for CORE VR

maximum current, ICCMAXA for GFX VR maximum

current, and TMPMAX for CORE VR maximum

temperature.

To set ICCMAX, ICCMAXA and TMPMAX, platform

designers should use resistive voltage dividers on these

three pins. The current of the divider should be several

milli-Amps to avoid noise effect. The three items share

the same algorithms : the ADC divides 5V into 255 levels.

Therefore, LSB = 5/255 = 19.6mV, which means 19.6mV

applied to ICCMAX pin equals to 1A setting. For example,

if a platform designer wants to set TMPMAX to 120

°C, the

voltage applied to TMPMAX should be 120 x 19.6mV =

2.352V. The ADC circuit inside these three pins will

decode the voltage applied and store the maximum current/

temperature setting into ICC_MAX and Temp_Max

registers. The ADC monitors and decodes the voltage at

these three pins only after EN = high. If EN = low, the

RT8167A will not take any action even when the VR output

current or temperature exceeds its maximum setting at

these ADC pins. The maximum level settings at these

ADC pins are different from over current protection or over

temperature protection. That means, these maximum level

setting pins are only for platform users to define their

system operating conditions and these messages will only

be utilized by the CPU.

Precise Reference Current Generation

The RT8167A includes extensive analog circuits inside

the controller. These analog circuits need very precise

reference voltage/current to drive these analog devices.

The RT8167A will auto-generate a 2.14V voltage source

at IBIAS pin, and a 53.6k

Ω resistor is required to be

connected between IBIAS and analog ground. Through

this connection, the RT8167A generates a 40

μA current

from IBIAS pin to analog ground and this 40

μA current will

be mirrored inside the RT8167A for internal use. Other

types of connection or other values of resistance applied

at the IBIAS pin may cause failure of the RT8167A's analog

circuits. Thus a 53.6k

Ω resistor is the only recommended

component to be connected to the IBIAS pin. The

resistance accuracy of this resistor is recommended to

be at least 1%.

Figure 4. IBIAS Setting

IBIAS

53.6k

Current

Mirror

2.14V

Power Ready Detection and Power On Reset (POR)

During start-up, the RT8167A detects the voltage on the

voltage input pins : VCC and EN. When VCC > VUVLO,

the RT8167A will recognize the power state of system to

be ready (POR = high) and wait for enable command at

EN pin. After POR = high and EN > VENTH, the RT8167A

will enter start-up sequence for both CORE VR and GFX

VR. If the voltage on any voltage pin drops below POR

threshold (POR = low), the RT8167A will enter power down

sequence and all the functions will be disabled. SVID will

be invalid within 300

μs after chip becomes enabled. All

the protection latches (OVP, OCP, UVP, OTP) will be

cleared only after POR = low. EN = low will not clear

these latches.

Figure 3. Power Ready Detection and Power On Reset

(POR)

VUVLO

VENTH

POR

Chip EN

VCC

RT8167A Datasheet(PDF) 29 Page - Richtek Technology Corporation

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