MAX17000A Maxim Integrated Products, MAX17000A Datasheet - Page 19

• Manufacturer Part Number: MAX17000A
• Description: Complete DDR2 and DDR3 Memory Power-Management Solution
• Manufacturer: Maxim Integrated Products

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Figure 3. Pulse-Skipping/Discontinuous Crossover Point
The low-noise forced-PWM mode (SKIP = V
the zero-crossing comparator, which controls the low-
side switch on-time. This forces the low-side gate-drive
waveform to constantly be the complement of the high-
side gate-drive waveform, so the inductor current
Figure 4. MAX17000A Standby Mode Timing
0
ΔI
Δt
=
ON-TIME
Forced-PWM Mode ( SKIP = V
V
IN
- V
SMPS OUTPUT
VTTR OUTPUT
VTT OUTPUT
VTT CURRENT LIMIT
PGOOD2
STANDBY TIMING
______________________________________________________________________________________
L
STDBY
PGOOD1
OUT
Complete DDR2 and DDR3 Memory
TIME
I
CC
LOAD
) disables
Power-Management Solution
= I
I
PEAK
PEAK
VTT HIGH-IMPEDANCE
/2
CC
)
reverses at light loads while DH maintains a duty factor
of V
a fairly constant switching frequency. However, forced-
PWM operation comes at a cost: the no-load 5V bias
current remains between 2mA to 20mA, depending on
the switching frequency.
STDBY = AGND overrides the SKIP pin setting, forcing
the MAX17000A into standby.
The MAX17000A switches to forced-PWM mode during
shutdown, regardless of the state of SKIP and STDBY
levels.
It should be noted that standby mode in the
MAX17000A corresponds to computer system standby
operation, and is not referring to the MAX17000A shut-
down status.
When standby mode is enabled (STDBY = AGND),
VTT is disabled (high impedance) but VTTR remains
active.
When standby mode is disabled (STDBY = V
VTT block is enabled and the VTT output capacitor is
charged. The VTT soft-start current limit increases lin-
early from zero to its maximum current limit in 160μs
(typ), keeping the input VTTI inrush low. See Figure 4.
OUT
/V
IN
. The benefit of forced-PWM mode is to keep
160μs
Standby Mode ( STDBY )
CC
), the
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