Rainbow Electronics MAX1712 - Manual (Page 9)

MAX1710/MAX1711/MAX1712
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
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Standard Application Circuit
The standard application circuit (Figure 1) generates a
low-voltage, high-power rail for supplying up to 7A to the
core CPU V
CC
in a notebook computer. This DC-DC
converter steps down a battery or AC adapter voltage to
sub-2V levels with high efficiency and accuracy, and
represents a good compromise between size, efficiency,
and cost.
See the MAX1710 EV kit manual for a list of components
and suppliers.
Detailed Description
The MAX1710/MAX1711/MAX1712 buck controllers are
targeted for low-voltage, high-current CPU power sup-
plies for notebook computers. CPU cores typically exhib-
it 0A to 10A or greater load steps when the clock is
throttled. The proprietary Quick-PWM pulse-width modu-
lator in the MAX1710/MAX1711/MAX1712 is specifically
designed for handling these fast load steps while main-
taining a relatively constant operating frequency and
inductor operating point over a wide range of input volt-
ages. The Quick-PWM architecture circumvents the poor
load-transient timing problems of fixed-frequency cur-
Pin Description (continued)
NAME FUNCTION
16
(MAX1711/
MAX1712)
D4 DAC Code Input, MSB. 5µA internal pullup to V CC (Tables 1, 2, and 3).
PIN
13 DL Low-Side Gate-Driver Output, swings 0 to V DD
12 PGOOD Open-Drain Power-Good Output
11 GNDS
Ground Remote-Sense Input, normally connected to ground directly at the load. GNDS internally con-
nects to the integrator that fine tunes the ground offset voltage.
10 GND Analog Ground
14 PGND Power Ground. Also used as the inverting input for the current-limit comparator.
15 V DD Supply Voltage Input for the DL Gate Driver, 4.5V to 5.5V
17 D3 DAC Code Input. 5µA internal pullup to V CC .
16
(MAX1710)
OVP
Overvoltage-Protection Disable Control Input (Table 4). GND = normal operation and overvoltage
protection active, V
CC = overvoltage protection disabled.
22 BST
Boost Flying-Capacitor Connection. An optional resistor in series with BST allows the DH pullup
current to be adjusted (Figure 5). This technique of slowing the LX rise time can be used to prevent
accidental turn-on of the low-side MOSFET due to excessive gate-drain capacitance.
21 SKIP
Low-Noise-Mode Selection Control Input. Low-noise forced-PWM mode causes inductor current
recirculation at light loads and suppresses pulse-skipping operation. Normal operation prevents
current recirculation. SKIP can also be used to disable both overvoltage and undervoltage protection
circuits and clear the fault latch (Figure 6). GND = normal operation, V
CC = low-noise mode. Do not
leave SKIP floating.
20 D0 DAC Code Input LSB. 5µA internal pullup.
19 D1 DAC Code Input. 5µA internal pullup.
18 D2 DAC Code Input. 5µA internal pullup.
24 DH High-Side Gate-Driver Output. Swings LX to BST.
23 LX
Inductor Connection. LX serves as the lower supply rail for the DH high-side gate driver. Also used
for the noninverting input to the current-limit comparator, as well as the skip-mode zero-crossing com-
parator.