MAX8717ETI+ Maxim Integrated Products, MAX8717ETI+ Datasheet - Page 16

• Manufacturer Part Number: MAX8717ETI+
• Description: IC CNTRLR PWR SUP 28-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8717ETI+

• Applications: Controller, Notebook Computers
• Voltage - Input: 4 ~ 26 V
• Number Of Outputs: 2
• Voltage - Output: 3.3V, 5V, 1 ~ 5.5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
The heart of each current-mode PWM controller is a
multi-input, open-loop comparator that sums two sig-
nals: the output-voltage error signal with respect to the
reference voltage and the slope-compensation
ramp (Figure 3). The MAX8716/MAX8717/MAX8756/
MAX8757 use a direct-summing configuration,
approaching ideal cycle-to-cycle control over the out-
put voltage without a traditional error amplifier and the
phase shift associated with it. The MAX8716/MAX8717/
MAX8756/MAX8757 use a relatively low loop gain,
allowing the use of low-cost output capacitors. The low
loop gain results in the 0.1% typical load-regulation
error and helps reduce the output capacitor size and
cost by shifting the unity-gain crossover frequency to a
lower level.
Figure 3. PWM-Controller Functional Diagram
16
SKIP
CSH
OSC
CSL
______________________________________________________________________________________
DECODE
SKIP
Current-Mode PWM Controller
(0.05 x V
LIMIT
0.1 x V
FOR MAX8756)
LIMIT
Fixed-Frequency,
-1.2 x V
0.2 x V
LIMIT
3mV
LIMIT
V
LIMIT
The FSEL input selects the PWM mode switching fre-
quency. Table 3 shows the switching frequency based
on the FSEL connection. High-frequency operation opti-
mizes the application for the smallest component size,
trading off efficiency due to higher switching losses.
This may be acceptable in ultra-portable devices where
the load currents are lower. Low-frequency operation
offers the best overall efficiency at the expense of com-
ponent size and board space.
To maintain low ripple fixed-frequency operation, drive
SKIP_ high to put the output into forced-PWM mode.
This disables the zero-crossing comparator and allows
negative inductor current. During forced-PWM mode,
AGND
SLOPE COMP
S
R
Q
R
S
Q
Frequency Selection (FSEL)
SOFT-START
SOFT-STOP
Forced-PWM Mode
DL DRIVER
FB
REF / 2
ON
DH DRIVER