Rainbow Electronics MAX1545 - Manual (Page 17)

MAX1519/MAX1545
Dual-Phase, Quick-PWM Controllers for
Programmable CPU Core Power Supplies
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Power-Up Sequence
The MAX1519/MAX1545 are enabled when SHDN is
driven high (Figure 2). The reference powers up first.
Once the reference exceeds its undervoltage lockout
threshold, the PWM controller evaluates the DAC target
and starts switching.
For the MAX1519/MAX1545, the slew-rate controller
ramps up the output voltage in 25mV increments to the
proper operating voltage (see Tables 3 and 4) set by
either D0–D4 (SUS = GND) or S0–S1 (SUS = REF or
high). The ramp rate is set with the R
TIME resistor (see
the Output Voltage Transition Timing section). The con-
troller pulls VROK low until at least 3ms after the
MAX1519/MAX1545 reach the target DAC code.
Shutdown
When SHDN goes low, the MAX1519/MAX1545 enter
low-power shutdown mode. VROK is pulled low imme-
diately, and the output voltage ramps down to 0V in
25mV increments at 4 times the clock rate set by
R
TIME :
t
f
V
V
SHDN
SLEW
DAC
LSB
≤

 

4
MAX1519/MAX1545
2-PHASE DESKTOP P4
MAX1519/MAX1545
4- PHASE DESKTOP P4 DESIGNATION
Circuit of Figure 1 Circuit of Figure 12
Input Voltage Range 7V to 24V 7V to 24V
VID Output Voltage
(D4–D0) 1.5V
(CODE = GND, D4–D0 = 01110)
1.5V
(CODE = GND, D4–D0 = 01110)
Suspend Voltage
(SUS, S0–S1) Not Used
(SUS = GND)
Not Used
(SUS = GND)
Maximum Load Current 60A 60A
Number of Phases ( η
TOTAL )
Two phases
(1) MAX1519/MAX1545
Four phases
(1) MAX1519/MAX1545 + (2) MAX1980
Inductor (per phase)
0.6µH
Panasonic ETQP1H0R6BFA
0.7µH Panasonic ETQP2H0R7BFA or
0.8µH Sumida CDEP105L-0R8
Switching Frequency 300kHz (TON = REF) 300kHz (TON = REF)
High-Side MOSFET
(N
H , per phase)
Siliconix (1) Si7886DP
International Rectifier (2) IRF6604
International Rectifier (1) IRF7811W or
Fairchild (1) FDS6694
Low-Side MOSFET
(N
L , per phase)
Siliconix (2) Si7442DP or
International Rectifier (2) IRF6603
Fairchild (2) FDS6688 or
Siliconix (1) Si7442DP
Total Input Capacitance (C IN )
(6) 10µF, 25V
Taiyo Yuden TMK432BJ106KM or
TDK C4532X5R1E106M
(6) 10µF, 25V
Taiyo Yuden TMK432BJ106KM or
TDK C4532X5R1E106M
Total Output Capacitance
(C
OUT )
(4) 680µF, 2.5V
Sanyo 2R5TPD680M
(4) 680µF, 2.5V
Sanyo 2R5TPD680M
Current-Sense Resistor
(R
SENSE , per phase)
1.0m Ω
Panasonic ERJM1WTJ1M0U
1.5m Ω
Panasonic ERJM1WTJ1M5U
Table 1. Component Selection for Standard Multiphase Applications*
*Contact Intel for the Mobile P4 specifications and contact Maxim for a reference schematic.