IR36021 datasheet(29/41 Pages) IRF

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IR36021

DIGITAL POL BUCK CONTROLLER with I2C AND PMBus

Interface

February 27, 2013 | Rev 3.5

Figure 35: OCP on Loop #2 shuts down both loops

Slow Current Limit

In addition to the (fast) OCP, a Slow Current Limit can be

programmed to monitor and protect against the long‐term

average current (Table 17). This allows the system designer

to operate closer to the TDP level (thermal design power)

of the system.

TABLE 17: SLOW OCP

MTP Register

Function

Slow_Imax = 0

Disabled

Slow_Imax = non‐zero

Slow OCP range 2A to 62A

per phase in 2A steps

The fast OCP threshold should be set reasonabely above

the slow OCP threshold to prevent the instantaneous

current spikes from tripping OCP. The fast OCP comparator

has a 60kHz low‐pass filter and the slow OCP comparator

has a LPF with a programable band‐width of 52Hz or 3.2Hz.

When the slow OCP is tripped, the VR will shut down based

upon the OCP behavior set in Table 16.

Note that the slow OCP protection is disabled during start

up and during VID transitions. In addition, depending on

the revision of the the GUI, the current thresholds for OCP

might be set per phase or per rail.

VR_HOT and Over Temperature Protection (OTP)

The IR36021 provides a temperature measurement

capability at the TSEN pin that is used for over

temperature protection, VR_HOT flag and temperature

monitoring on loop one. The temperature is measured

with an NTC network that can be positioned close to

thermal hot spot. The thresholds are programmable in

1°C increments as shown in Table 18. If the measured

temperature exceeds the OTP threshold, the IR36021 will

latch off the VR (cycle system power or ENABLE to restart).

TABLE 18: VR_HOT & OTP

Function

VR_HOT polarity

VR_HOT threshold (64°C to 127°C)

OTP threshold (VR_HOT + 0°C to 32°C) max

134°C

The IR36021 includes a pre‐programmed look‐up table that

is optimized for the recommended NTC options shown in

Table 19. The NTC network is connected to the TSEN pin as

shown in Figure 36. A 0.01uF capacitor is recommended to

filter noise.

TABLE 19: NTC TEMPERATURE SENSE RANGE

NTC

Value

Rparallel

Murata NCP15WB473F03RC or

Panasonic ERT‐J0EP473J

47KΩ

13KΩ

TSEN

100µA

Rparallel

RNTC

0.01µF

5 ohm

Figure 36: Temperature Sense NTC Network

Icritical Flag

The IR36021 VR_HOT_ICRIT pin can be optionally

programmed to assert when a user programmable output

current level is exceeded. The assertion is not a fault and

the VR continues to regulate. I_CRITICAL monitors a long

term averaged output current which is a useful indicator of

average operating current and thermal operation. The user

can select between two I_CRITICAL filters bandwidths,

which is called telemetry‐BW. Telemetry‐BW affects other

readings/measurements like: slow‐OCP, Vin/Vout reading,

and temperature measurement. (Table 20).

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