MAX1717 Maxim, MAX1717 Datasheet - Page 21

• Manufacturer Part Number: MAX1717
• Description: Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUs
• Manufacturer: Maxim

for each of the CPU’s grounded VID pins. This quies-
cent current can be avoided by taking advantage of the
fact that D0–D4 need only appear low impedance
briefly, not necessarily on a continuous DC basis. High-
impedance pull-ups can also be used if they are
bypassed with a large enough capacitance to make
them appear low impedance for the 4µs sampling inter-
val. As noted in Figure 10, 4.7nF capacitors allow the
inputs to appear low impedance even though they are
pulled up with 1MΩ resistors.
The MAX1717 is designed to perform output voltage
transitions in a controlled manner, automatically mini-
mizing input surge currents. This feature allows the cir-
cuit designer to achieve nearly ideal transitions,
guaranteeing just-in-time arrival at the new output volt-
age level with the lowest possible peak currents for a
given output capacitance. This makes the IC very suit-
able for CPUs featuring SpeedStep technology and
Figure 8. Internal Mux B-Mode Data Test and Latch
Output Voltage Transition Timing
3.0V TO 5.5V
Step-Down Controller for Notebook CPUs
______________________________________________________________________________________
Dynamically Adjustable, Synchronous
100k
D4
D3
D2
D1
D0
40k
8k
Figure 7. Using the Internal Mux with Hard-Wired A-Mode and
B-Mode DAC Codes
40k
8k
A-MODE VID =
01101 → 1.35V
40k
8k
3.0V TO 5.5V
40k
8k
40k
8k
+5V
100k
B-MODE VID =
01000 → 1.60V
GND
V
CC
MAX1717
B-DATA
LATCH
D4
D3
D2
D1
D0
MAX1717
A/B
A/B = LOW = 1.60V
A/B = HIGH = 1.35V
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