Datasheet

MAX8650
4.5V to 28V Input Current-Mode Step-Down
Controller with Adjustable Frequency
8 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 FSYNC
Frequency Set and Synchronization. Connect a resistor from FSYNC to GND to set the switching
frequency, or drive with an external clock signal between 160kHz and 1.2MHz. See the Switching
Frequency and Synchronization section.
2 MODE
Current-Limit Operating-Mode Selection. Connect MODE to AVL for latch-off current limit or connect
MODE to GND for automatic-recovery current limit.
3 SYNCO
Synchronization Output. Provides a clock output that is 180° out-of-phase with the internal oscillator
for synchronizing another MAX8650.
4 BST Boost Capacitor Connection. Connect a 0.1µF ceramic capacitor from BST to LX.
5DH
High-Side n-Channel MOSFET Gate-Driver Output. Connect DH to the gate of the high-side MOSFET.
DH is internally pulled low in shutdown.
6 LX External Inductor Connection
7DL
Low-Side n-Channel MOSFET Gate-Driver Output. Connect DL to the gate of the low-side MOSFET
(synchronous rectifier). DL is internally pulled low in shutdown.
8 PGND
Power Ground. Connect PGND to the power ground plane and to the source of the low-side external
MOSFET. The return path for both gate drivers is through PGND.
9VL
Inter nal 6.5V Li near - Reg ul ator Outp ut. C onnect a 1µF to 10µF cer am i c cap aci tor fr om V L to g r ound . For
V
IN
< 7V , connect V L d i r ectl y to IN . V L p ow er s b oth g ate d r i ver s. V L i s the i np ut to the AV L l i near r eg ul ator .
10 IN Input Supply Voltage. IN is the input to the VL linear regulator. Connect VL to IN for V
IN
< 7V.
11 EN
Enable. Apply logic-high to enable the output, or logic-low to put the controller in low-power shutdown
mode. Connect EN to IN for always-on operation.
12 AVL
Internal 5V Linear-Regulator Output. Connect a 1µF ceramic capacitor from AVL to ground. AVL
powers the MAX8650’s internal circuits.
13 GND
Ground. Connect GND to the analog ground plane. Connect the analog ground and power ground
planes at a single point near the IC. Low-current signals return to GND.
14 CS+ Positive Differential Current-Sense Input
15 CS- Negative Differential Current-Sense Input
16 ILIM1
Programmable Current-Limit Input for Inductor Current. Connect a resistor from ILIM1 to GND to set
the peak current-limit threshold. ILIM1 sources 10µA through the resistor, and the voltage at ILIM1 is
attenuated 7.5:1 to set the final current limit. For example, a 60kΩ resistor results in 600mV at ILIM1.
This results in a current-limit threshold (V
CS+
- V
CS-
) of 80mV. The ILIM1 resistor range is 24kΩ to
60kΩ. Connect ILIM1 to AVL to set the default current-limit threshold of 80mV.