ISL62883HRTZ-T Datasheet, PDF (17/37 Pages) Intersil Corporation – Multiphase PWM Regulator for IMVP-6.5™ Mobile CPUs

ISL62883, ISL62883B
Modes of Operation
TABLE 2. ISL62883 MODES OF OPERATION
CONFIGURATION
PSI#
DPRSLPVR
OPERATIONAL
MODE
3-phase Configuration
0
0
2-phase CCM
0
1
1-phase DE
1
0
3-phase CCM
1
1
1-phase DE
2-phase Configuration
0
0
1-phase CCM
0
1
1-phase DE
1
0
2-phase CCM
1
1
1-phase DE
1-phase Configuration
0
0
1-phase CCM
0
1
1-phase DE
1
0
1-phase CCM
1
1
1-phase DE
Table 2 shows the ISL62883 operational modes, programmed by
the logic status of the PSI# and the DPRSLPVR pins. In 3-phase
configuration, the ISL62883 enters 2-phase CCM for (PSI# = 0 and
DPRSLPVR = 0) by dropping PWM3 and operating phases 1 and 2
180° out-of-phase. It also reduces the overcurrent and the
way-overcurrent protection levels to 2/3 of the initial values. The
ISL62883 enters 1-phase DE mode when DPRSLPVR = 1. It drops
phases 2 and 3, and reduces the overcurrent and the way-
overcurrent protection levels to 1/3 of the initial values.
In 2-phase configuration, the ISL62883 enters 1-phase CCM for
(PSI# = 0 and DPRSLPVR = 0). It drops Phase-2 and reduces the
overcurrent and the way-overcurrent protection levels to 1/2 of
the initial values. The ISL62883 enters 1-phase DE mode when
DPRSLPVR = 1 by dropping phase 2.
In 1-phase configuration, the ISL62883 does not change the
operational mode when the PSI# signal changes status. It enters
1-phase DE mode when DPRSLPVR = 1.
Dynamic Operation
The ISL62883 responds to VID changes by slewing to the new
voltage at 5mV/µs slew rate. As the output approaches the VID
command voltage, the dv/dt moderates to prevent overshoot.
Geyserville-III transitions commands one LSB VID step (12.5mV)
every 2.5µs, controlling the effective dv/dt at 5mv/µs. The
ISL62883 is capable of 5mV/µs slew rate.
When the ISL62883 is in DE mode, it will actively drive the output
voltage up when the VID changes to a higher value. It’ll resume
DE mode operation 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
ISL62883 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.
During load insertion response, the Fast Clock function increases
the PWM pulse response speed. The ISL62883 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 R³â„¢ modulator intrinsically has voltage feed forward. The
output voltage is insensitive to a fast slew rate input voltage
change.
Protections
The ISL62883 provides overcurrent, current-balance,
undervoltage, overvoltage, and over-temperature protections.
The ISL62883 determines overcurrent protection (OCP) by
comparing the average value of the droop current I_droop with an
internal current source threshold. It declares OCP when I_droop is
above the threshold for 120µs. A resistor R_comp from the COMP
pin to GND programs the OCP current source threshold, as Table 3
shows. It is recommended to use the nominal R_comp value. The
ISL62883 detects the R_comp value at the beginning of start up,
and sets the internal OCP threshold accordingly. It remembers the
R_comp value until the VR_ON signal drops below the POR
threshold.
TABLE 3. ISL62883 OCP THRESHOLD
R_comp
NOMINAL
MIN. (kΩ) (kΩ)
MAX.
(kΩ)
OCP THRESHOLD (µA)
1-PHASE 2-PHASE 3-PHASE
MODE
MODE
MODE
none
none
20
40
60
320
400
480
22.7
45.3
68
210
235
260
20.7
41.3
62
155
165
175
18
36
54
104
120
136
20
37.33
56
78
85
92
22.7
38.7
58
62
66
70
20.7
42.7
64
45
50
55
18
44
66
The default OCP threshold is the value when R_comp is not
populated. It is recommended to scale the droop current I_droop
such that the default OCP threshold gives approximately the
desired OCP level, then use R_comp to fine tune the OCP level if
necessary.
For overcurrent conditions above 2.5 times 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 ISL62883 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 ISL62883 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 dessert PGOOD.
The ISL62883 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
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FN6891.4
June 21, 2011