TM
MP2104 – 1.7MHz 600mA SYNCHRONOUS STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin # Name Description
1
2
3
4
5
5
Regulator Enable Control Input. Drive EN above 1.5V to turn on the MP2104. Drive EN below
0.3V to turn it off (shutdown current < 0.1µA).
GND Ground.
SW Power Switch Output. Inductor connection to drains of the internal PFET and NFET switches.
IN
Supply Input. Bypass to GND with a 2.2µF or greater ceramic capacitor.
Feedback Input (MP2104DJ). Connect FB to the center point of the external resistor divider. The
FB
feedback threshold voltage is 0.6V.
Output Voltage Sense Input (MP2104DJ-1.5 and MP2104DJ-1.8). An internal resistor divider is
OUT
connected to this pin to set the proper output voltage.
EN
OPERATION
The MP2104 is a constant frequency current
mode PWM step-down converter. The MP2104
is optimized for low voltage, Li-Ion battery
powered applications where high efficiency and
small size are critical. The MP2104 uses an
external resistor divider to set the output
voltage from 0.6V to 6V. The device integrates
both a main switch and a synchronous rectifier,
which provides high efficiency and eliminates
IN
+
IAMP
10X
--
CURRENT
SENSE
AMP
PWM
DH
MAIN
SWITCH
(PCH)
PWM
CONTROL
LOGIC
SW
SYNCHRONOUS
RECTIFIER
(NCH)
DL
an external Schottky diode. The MP2104 can
achieve 100% duty cycle. The duty cycle D of a
step-down converter is defined as:
D
=
T
ON
×
f
OSC
×
100%
≈
V
OUT
×
100%
V
IN
Where T
ON
is the main switch on time, f
OSC
is
the oscillator frequency (1.7MHz), V
OUT
is the
output voltage and V
IN
is the input voltage.
EN
BIAS
&
VOLTAGE
REFERENCE
ICS
+
SLOPE COMP
EAO
0.6V
FEEDBACK
ERROR EAMP
AMP
--
+
+
PWMCMP
--
FB
CC
17pF
1.7MHz
OSCILLATOR
OSC
GND
MP2104_BD01
Figure 1—Functional Block Diagram (MP2104)
MP2104 Rev. 1.3
10/4/2005
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6
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