MAX17036 Maxim Integrated Products, MAX17036 Datasheet - Page 30

• Manufacturer Part Number: MAX17036
• Description: (MAX17030 / MAX17036) 1/2/3-Phase Quick-PWM IMVP-6.5 VID Controllers
• Manufacturer: Maxim Integrated Products

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1/2/3-Phase Quick-PWM
IMVP-6.5 VID Controllers
When pulse-skipping, the controller blanks the upper
PWRGD and CLKEN thresholds. Upon entering pulse-
skipping operation, the controller temporarily sets the
OVP threshold to 1.5V, preventing false OVP faults
when the transition to pulse-skipping operation coin-
cides with a VID code change. Once the error amplifier
detects that the output voltage is in regulation, the OVP
threshold tracks the selected VID DAC code. The
MAX17030/MAX17036 automatically use forced-PWM
operation during soft-start and soft shutdown, regard-
less of the DPRSLPVR and PSI configuration.
In skip mode (DPRSLPVR = high), an inherent automatic
switchover to PFM takes place at light loads (Figure 8).
This switchover is affected by a comparator that trun-
cates the low-side switch on-time at the inductor cur-
rent’s zero crossing. The zero-crossing comparator
senses the inductor current across the low-side
MOSFETs. Once V
comparator threshold (see the Electrical Characteristics ),
the comparator forces DL low. This mechanism causes
the threshold between pulse-skipping PFM and non-
skipping PWM operation to coincide with the boundary
between continuous and discontinuous inductor-current
operation. The PFM/PWM crossover occurs when the
load current of each phase is equal to 1/2 the peak-to-
peak ripple current, which is a function of the inductor
value (Figure 8). For a battery input range of 7V to 20V,
this threshold is relatively constant, with only a minor
dependence on the input voltage due to the typically
Figure 9. Power-Up and Shutdown Sequence Timing Diagram
30
______________________________________________________________________________________
PWM CONTROL
VID (D0–D6)
INTERNAL
IMVPOK
CLKEN
Automatic Pulse-Skipping Switchover
SHDN
V
CORE
1/4 SLEW RATE SET
V
CC
LX
SOFT-START
BY R
drops below the zero-crossing
TIME
IGNORE
60µs TYP
VID
PULSE-SKIPPING
t
BLANK
t
20µs TYP
BLANK
low duty cycles. The total load-current at the PFM/PWM
crossover threshold (I
The MAX17030/MAX17036 are enabled when SHDN is
driven high (Figure 9). The reference powers up first.
Once the reference exceeds its undervoltage-lockout
(UVLO) threshold, the internal analog blocks are turned
on and masked by a 150µs one-shot delay. The PWM
controller then begins switching.
Figure 8. Pulse-Skipping/Discontinuous Crossover Point
t
5ms TYP
BLANK
0
I
LOAD SKIP
∆I
∆t
Power-Up Sequence (POR, UVLO)
ON-TIME
(
=
FORCED-PWM
V
IN
)
– V
=
20µs TYP
L
⎛
⎝ ⎜
OUT
t
LOAD(SKIP)
BLANK
T
IGNORE
SW OUT
VID
V
L
TIME
SOFT-SHUTDOWN
1/4 SLEW RATE SET
BY R
) is approximately:
⎞
⎠ ⎟
⎛
⎝ ⎜
TIME
V
IN
2
-
×
V
V
OUT
IN
I
LOAD
I
PEAK
⎞
⎠ ⎠ ⎟
= I
PEAK
/2