Interleaved High-Efficiency, Dual Power-Supply
Controllers for Notebook Computers
Pin Description (continued)
Low-Side Gate-Driver Output for SMPS2. DL2 swings from PGND to VDD.
Supply Voltage Input for the DL_ Gate Drivers. Connect to a 5V supply.
Power and Analog Ground. Connect backside pad to GND.
Analog Ground. Connect backside pad to AGND.
Low-Side Gate-Driver Output for SMPS1. DL1 swings from PGND to VDD.
Inductor Connection for SMPS1. Connect LX1 to the switched side of the inductor. LX1
is the lower supply rail for the DH1 high-side gate driver.
High-Side Gate-Driver Output for SMPS1. DH1 swings from LX1 to BST1.
Boost Flying Capacitor Connection for SMPS1. Connect to an external capacitor and
diode as shown in Figure 1. An optional resistor in series with BST1 allows the DH1 turn-
on current to be adjusted.
Positive Current-Sense Input for SMPS1. Connect to the positive terminal of the current-
sense element. Figure 8 describes two different current-sensing options.
Negative Current-Sense Input for SMPS1. Connect to the negative terminal of the
current-sense element. Figure 8 describes two different current-sensing options.
Feedback Input for SMPS1. Connect FB1 to VCC for fixed 3.3V output. In adjustable
mode, FB1 regulates to 1V.
SMPS1 Open-Drain Power-Good Output. PGOOD1 is low when SMPS1 is more than
10% below its regulation threshold, during soft-start, and in shutdown.
SMPS1 Peak Current-Limit Threshold Adjustment. Connect ILIM1 to VCC to enable the
default 50mV current-limit threshold. In adjustable mode, the current-limit threshold
across CSH1 and CSL1 is precisely 1/10th the voltage seen at ILIM1 over a 500mV to
2.0V range. The logic threshold for switchover to the 50mV default value is
approximately VCC - 1V.
Exposed Pad. Connect exposed backside pad to analog ground.
The MAX8716/MAX8717/MAX8757 Standard Application
Circuit (Figure 1) generates the 5V/5A and 3.3V/5A typi-
cal of the main supplies in notebook computers. The
input supply range is 6V to 24V. See Table 1 for compo-
nent selections, while Table 2 lists the compo-
The MAX8716/MAX8717/MAX8757 contain two inter-
leaved fixed-frequency, step-down controllers
designed for low-voltage power supplies. The optimal
interleaved architecture guarantees out-of-phase oper-
ation, which reduces the input capacitor ripple.
SMPS 5V Bias Supply (VCC and VDD)
The MAX8716/MAX8717/MAX8757 switch-mode power
supplies (SMPS) require a 5V bias supply in addition to
the high-power input supply (battery or AC adapter).
VDD is the power rail for the MOSFET gate drive, and
VCC is the power rail for the IC. Connect the external
4.5V to 5.5V supply directly to VDD and connect VDD to
VCC through an RC filter, as shown in Figure 1. The
maximum supply current required is:
IBIAS = ICC + fSW (QG(NL1) + QG1(NH1) +QG2(NL2) +
QG2(NH2)) = 1.3mA to 40mA
where ICC is 1.3mA, fSW is the switching frequency,
and QG_ are the MOSFET data sheet’s total gate-
charge specification limits at VGS = 5V.