MAX17000AETG+ Maxim Integrated Products, MAX17000AETG+ Datasheet - Page 19

• Manufacturer Part Number: MAX17000AETG+
• Description: IC PWM CTLR DDR/DDR2/DDR3 24TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17000AETG+

• Applications: Memory, DDR2/DDR3 Regulator
• Current - Supply: 2mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX17000 always uses skip mode during startup,
regardless of the SKIP and STDBY setting. The SKIP
and STDBY controls take effect after soft-start is done.
See Figure 3.
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
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
Figure 3. Pulse-Skipping/Discontinuous Crossover Point
Figure 4. MAX17000 Standby Mode Timing
OUT
0
/V
∆I
∆t
IN
=
. The benefit of forced-PWM mode is to keep
ON-TIME
V
Forced-PWM Mode ( SKIP = V
IN
- V
L
STDBY
SMPS_RUNOK
SMPS OUTPUT
VTTR OUTPUT
VTT OUTPUT
VTT CURRENT LIMIT
PGOOD1
PGOOD2
______________________________________________________________________________________
OUT
TIME
Complete DDR2 and DDR3 Memory
I
LOAD
CC
= I
) disables
Power-Management Solution
I
PEAK
PEAK
VTT HIGH IMPEDANCE
/2
CC
)
current remains between 2mA to 20mA, depending on
the switching frequency.
STDBY = AGND overrides the SKIP pin setting, forcing
the MAX17000 into standby.
The MAX17000 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 MAX17000
corresponds to computer system standby operation,
and is not referring to the MAX17000 shutdown status.
When standby mode is enabled (STDBY = AGND), the
MAX17000 switches over from the fast internal PWM
block to a low-quiescent current mode using a low-
power valley comparator to initiate an on-time pulse.
The zero-crossing comparator is enabled so that the
MAX17000 only operates in discontinuous mode,
reducing the maximum available output current by 1/6.
The system is NOT expected to have any fast load tran-
sients in such a state. While in standby, VTT is disabled
(high impedance) but VTTR remains active. SKIP is
ignored when standby mode is enabled.
When standby mode is disabled (STDBY = V
MAX17000 reenables its fast internal PWM block. Once
the internal SMPS block is ready, the VTT block is
enabled and the VTT output capacitor is charged. The
VTT soft-start current limit increases linearly from zero
to its maximum current limit in 160µs (typ), keeping the
input VTTI inrush low. See Figure 4.
< 50µs
160µs
Standby Mode ( STDBY )
CC
), the
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