Rainbow Electronics MAX17000 User Manual

Page 21

MAX17000

Complete DDR2 and DDR3 Memory

Power-Management Solution

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Soft-shutdown begins after SHDN goes low, an output
undervoltage fault occurs, or a thermal fault occurs. A
fault on the SMPS (UV fault for more than 200μs (typ)),
or fault on the VTT output that persists for more than
5ms (typ), triggers shutdown of the whole IC. During
soft-shutdown, the output is ramped down to 0V in
2.8ms, reducing negative inductor currents that can
cause negative voltages on the output. At the end of
soft-shutdown, DL is driven low.

When OVP is enabled (OVP = V

), the internal 16

discharging MOSFETs on CSL and VTT are enabled
until startup is triggered again by a rising edge of
SHDN. When OVP is disabled (OVP = AGND), the CSL
and VTT internal 16

Ω discharging MOSFETs are not

enabled in shutdown.

Output Fault Protection

The MAX17000 provides overvoltage/undervoltage fault
protections for the PWM output. Drive OVP to enable
and disable fault protection as shown in Table 4.

STDBY

INT_REF

SMPS OUTPUT

REFOK

SMPS_RUNOK

PGOOD1

160

μs

SHDN

VTT OUTPUT

VTTR OUTPUT

VTT CURRENT LIMIT

PGOOD2

1.4ms

2.8ms

VTT 16

Ω FET

SKIP

FPWM

CSL 16

Ω FET

25mV

Figure 6. MAX17000 Startup/Shutdown Timing when OVP Is Enabled