MAX1556ETB+T Maxim Integrated Products, MAX1556ETB+T Datasheet - Page 9

• Manufacturer Part Number: MAX1556ETB+T
• Description: IC PWM STEP-DN DC-DC CONV 10TDFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1556ETB+T

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.75 ~ 5.5 V
• Current - Output: 1.2A
• Frequency - Switching: 1MHz
• Voltage - Input: 2.6 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TDFN Exposed Pad
• Power - Output: 1.95W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 2. Inductor Selection
R
for a few recommended inductors is listed in Table 2.
The MAX1556/MAX1556A/MAX1557 use soft-start to
eliminate inrush current during startup, reducing tran-
sients at the input source. Soft-start is particularly use-
ful for higher-impedance input sources such as Li+ and
alkaline cells. Connect the required soft-start capacitor
from SS to GND. For most applications using a 22µF
output capacitor, connect a 1000pF capacitor from SS
to GND. If a larger output capacitor is used, then use
the following formula to find the value of the soft-start
capacitor:
Soft-start is implemented by exponentially ramping up
the output voltage from 0 to V
stant equal to C
Operating Characteristics ). Assuming three time con-
stants to full output voltage, use the following formula to
calculate the soft-start time:
Connecting SHDN to GND or logic low places the
MAX1556/MAX1556A/MAX1557 in shutdown mode and
reduces supply current to 0.1µA. In shutdown, the con-
trol circuitry and the internal p-channel and n-channel
MOSFETs turn off and LX becomes high impedance.
Connect SHDN to IN or logic high for normal operation.
* Estimated based upon similar-valued prototype inductors.
MANUFACTURER
Taiyo Yuden
Taiyo Yuden
TOKO
TOKO
Sumida
TOKO
Murata
Sumitomo
Sumitomo
DS(ON)P
V
DROPOUT
is given in the Electrical Characteristics . DCR
t
SS
_______________________________________________________________________________________
SS
= I
C
= 600
LMNP04SB3R3N
LMNP04SB4R7N
D52LC
D52LC
CDRH3D16
D412F
LQH32CN
CXL180
CXLD140
SS
times 200kΩ (see the Typical
OUT
PART
=
x (R
x
22000
C
OUT(NOM)
10
OUT
DS(ON)P
3
x C
Shutdown Mode
SS
VALUE (µH)
+ DCR)
with a time con-
Soft-Start
3.3
4.7
3.5
4.7
4.7
4.7
4.7
4.7
4.7
16µA I
DCR (mΩ)
100*
100*
70*
36
50
73
87
50
97
As soon as the junction temperature of the
MAX1556/MAX1556A/MAX1557 exceeds +160°C, the
ICs go into thermal shutdown. In this mode the internal
p-channel switch and the internal n-channel synchro-
nous rectifier are turned off. The device resumes nor-
mal operation when the junction temperature falls
below +145°C.
The MAX1556/MAX1556A/MAX1557 are optimized for
use with small external components. The correct selec-
tion of inductors and input and output capacitors
ensures high efficiency, low output ripple, and fast tran-
sient response.
The MAX1556/MAX1556A/MAX1557 offer preset output
voltages of 1.0V, 1.2V, 1.3V, 1.5V, 1.8V, 2.5V, and 3.3V
as well as an adjustable output using external resistors.
Whenever possible, the preset outputs (set by D1 and
D2) should be used. With external resistor feedback,
noise coupling to FB can cause alternate LX pulse to
terminate early resulting in an inductor current wave-
form with alternate large and small current pulses. See
the External Feedback Switching Waveforms graph in
Typical Operating Characteristics section. Note that
external feedback and the alternating large-small pulse
waveform do not impact loop stability and have no
harmful effect on regulation or reliability.
The adjustable output is selected when D1 = D2 = 0
and an external resistor-divider is used to set the output
voltage (see Figure 6). The MAX1556/MAX1557 have a
defined line- and load-regulation slope. The load regu-
lation is for both preset and adjustable outputs and is
described in the Electrical Characteristics table and
Figures 4 and 5. The impact of the line-regulation slope
Step-Down Converters
Q
, 1.2A PWM DC-DC
I
SAT
1200*
1000*
1300
1200
1340
1140
1200
800*
790
Applications Information
(mA)
Adjusting the Output Voltage
3.8 x 3.8 x 1.8
4.8 x 4.8 x 1.2
2.5 x 3.2 x 2.0
3.0 x 3.2 x 1.7
2.8 x 3.2 x 1.5
SIZE (mm)
5 x 5 x 2.0
5 x 5 x 2.0
5 x 5 x 2.0
5 x 5 x 2.0
Thermal Shutdown
SHIELDED
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
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