MAX8643 Maxim Integrated Products, MAX8643 Datasheet - Page 7

• Manufacturer Part Number: MAX8643
• Description: 2MHz Step-Down Regulator
• Manufacturer: Maxim Integrated Products

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14, 15, 16
21, 22, 23
17–20
PIN
1, 7
3, 4
10
11
12
13
24
—
2
5
6
8
9
PWRGD
NAME
REFIN
COMP
PGND
CTL1,
FREQ
CTL2
GND
OUT
V
BST
EN
SS
FB
LX
EP
IN
DD
_______________________________________________________________________________________
Analog Circuit Ground
Supply Voltage and Bypass Input. Connect V
capacitor from V
Preset Output Voltage Selection Input. CTL1 and CTL2 set the output voltage to one of nine preset
voltages. See Table 1 for preset voltages.
External Reference Input. Connect REFIN to SS to use the internal 0.6V reference. Connecting REFIN to an
external reference voltage forces FB to regulate the voltage applied to REFIN. REFIN is internally pulled to
GND when the IC is in shutdown mode.
Soft-Start Input. Connect a capacitor from SS to GND to set the startup time. See the Soft-Start and REFIN
section for details on setting the soft-start time.
Output of the Voltage-Error Amplifier. Connect the necessary compensation network from COMP to FB.
COMP is internally pulled to GND when the IC is in shutdown mode.
Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to GND to set
the output voltage from 0.6V to 90% of V
CTL1 and CTL2 to select any of nine preset voltages.
Output Voltage Sense. Connect to the output. Leave OUT unconnected when an external resistor-divider
is used.
Oscillator Frequency Selection. Connect a resistor from FREQ to GND to select the switching frequency.
P ow er - G ood O utp ut. O p en- d r ai n outp ut that i s hi g h i m p ed ance w hen V
i nter nal l y p ul l ed l ow w hen V
IC i s i n shutd ow n m od e, V
High-Side MOSFET Driver Supply. Bypass BST to LX with a 0.1µF capacitor.
Inductor Connection. All LX pins are internally connected together. Connect all LX pins to the output
inductor. LX is high impedance when the IC is in shutdown mode.
Power Ground. Connect all PGND pins externally to the power ground plane.
Power-Supply Input. Input supply range is from 2.35V to 3.6V. Bypass with 22µF ceramic capacitance to
PGND externally. See the Typical Application Circuit.
Enable Input. Logic input to enable/disable the MAX8643.
Exposed Paddle. Connect to a large ground plane to optimize thermal performance.
DD
to GND.
3A, 2MHz Step-Down Regulator
D D
F B
or V
fal l s b el ow 90% of i ts r eg ul ati on p oi nt. P W RG D i s i nter nal l y p ul l ed l ow w hen the
I N
i s b el ow the U V LO thr eshol d , or the IC i s i n ther m al shutd ow n.
with Integrated Switches
IN
. Connect FB through an RC network to the output when using
DD
FUNCTION
to IN with a 10Ω resistor. Connect a 1µF ceramic
F B
≥ 90% of V
Pin Description
R E F IN
or 0.6V . P W RGD i s
7