isl62883c Intersil Corporation, isl62883c Datasheet - Page 21

• Manufacturer Part Number: isl62883c
• Description: Multiphase Pwm Regulator For Imvp-6.5? Mobile Cpus And Gpus
• Manufacturer: Intersil Corporation

(kΩ)
MIN
When the ISL62883C is in DE mode, it will actively drive
the output voltage up when the VID changes to a higher
value. The DE mode operation will resume after reaching
the new voltage level. If the load is light enough to
warrant DCM, it will enter DCM after the inductor current
has crossed zero for four consecutive cycles. The
ISL62883C will remain in DE mode when the VID
changes to a lower value. The output voltage will decay
to the new value and the load will determine the slew
rate. Overvoltage protection is blanked during VID down
transition in DE mode until the output voltage is within
60mV of the VID value.
During load insertion response, the Fast Clock function
increases the PWM pulse response speed. The
ISL62883C monitors the VSEN pin voltage and compares
it to 100ns-filtered version. When the unfiltered version
is 20mV below the filtered version, the controller knows
there is a fast voltage dip due to load insertion, hence
issues an additional master clock signal to deliver a PWM
pulse immediately.
The R
feed-forward. The output voltage is insensitive to a fast
slew rate input voltage change.
Protections
The ISL62883C provides overcurrent, current-balance,
undervoltage, overvoltage, and over-temperature
protections.
The ISL62883C determines overcurrent protection
(OCP) by comparing the average value of the droop
current I
It declares OCP when I
120µs. A resistor R
programs the OCP current source threshold, as well as
the overshoot reduction function in 1-phase
configuration, as Table 4 shows. It is recommended to
use the nominal R
the R
the internal OCP threshold accordingly. It remembers
the R
POR threshold.
320
210
155
104
78
62
45
TABLE 4. ISL62883C R
R
NOM
(kΩ)
none none
comp
comp
400
235
165
120
comp
3™
85
66
50
droop
modulator intrinsically has voltage
MAX
(kΩ)
value until the VR_ON signal drops below the
value at the beginning of start-up, and sets
480
260
175
136
92
70
55
with an internal current source threshold.
3-PHASE
CONFIG.
comp
comp
60
68
62
54
56
58
64
66
OCP THRESHOLD
droop
value. The ISL62883C detects
from the COMP pin to GND
21
2-PHASE
CONFIG.
comp
(µA)
37.33
45.3
41.3
38.7
42.7
is above the threshold for
40
36
44
PROGRAMMABILITY
1-PHASECONFIG.
60
68
62
54
60
68
62
54
OVERSHOOT
REDUCTION
FUNCTION
Disabled
Enabled
ISL62883C
The default OCP threshold is the value when R
populated. It is recommended to scale the droop current
I
approximately the desired OCP level, then use R
fine tune the OCP level if necessary.
For overcurrent conditions above 2.5x the OCP level, the
PWM outputs will immediately shut off and PGOOD will
go low to maximize protection. This protection is also
referred to as way-overcurrent protection or
fast-overcurrent protection, for short-circuit protections.
The ISL62883C monitors the ISEN pin voltages to
determine current-balance protection. If the ISEN pin
voltage difference is greater than 9mV for 1ms, the
controller will declare a fault and latch off.
The ISL62883C will declare undervoltage (UV) fault and
latch off if the output voltage is less than the VID set
value by 300mV or more for 1ms. It’ll turn off the PWM
outputs and de-assert PGOOD.
The ISL62883C has two levels of overvoltage
protections. The first level of overvoltage protection is
referred to as PGOOD overvoltage protection. If the
output voltage exceeds the VID set value by +200mV for
1ms, the ISL62883C will declare a fault and de-assert
PGOOD.
The ISL62883C takes the same actions for all of the
above fault protections: de-assertion of PGOOD and
turn-off of the high-side and low-side power MOSFETs.
Any residual inductor current will decay through the
MOSFET body diodes. These fault conditions can be reset
by bringing VR_ON low or by bringing V
POR threshold. When VR_ON and V
high operating levels, a soft-start will occur.
The second level of overvoltage protection is different.
If the output voltage exceeds 1.55V, the ISL62883C will
immediately declare an OV fault, de-assert PGOOD, and
turn on the low-side power MOSFETs. The low-side
power MOSFETs remain on until the output voltage is
pulled down below 0.85V when all power MOSFETs are
turned off. If the output voltage rises above 1.55V
again, the protection process is repeated. This behavior
provides the maximum amount of protection against
shorted high-side power MOSFETs while preventing
output ringing below ground. Resetting VR_ON cannot
clear the 1.55V OVP. Only resetting V
1.55V OVP is active all the time when the controller is
enabled, even if one of the other faults have been
declared. This ensures that the processor is protected
against high-side power MOSFET leakage while the
MOSFETs are commanded off.
The ISL62883C has a thermal throttling feature. If the
voltage on the NTC pin goes below the 1.18V OT
threshold, the VR_TT# pin is pulled low indicating the
need for thermal throttling to the system. No other
action is taken within the ISL62883C in response to NTC
pin voltage.
Table 5 summarizes the fault protections.
droop
such that the default OCP threshold gives
DD
DD
return to their
DD
will clear it. The
below the
comp
March 18, 2010
comp
FN7557.1
is not
to