Rainbow-electronics MAX17000 Manual do Utilizador descarregar pdf (Página 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 16Ω

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 16Ω 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

160μs

SHDN

VTT OUTPUT

VTTR OUTPUT

VTT CURRENT LIMIT

PGOOD2

1.4ms

2.8ms

VTT 16Ω FET

SKIP FPWM

CSL 16Ω FET

25mV

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

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 30 31

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