MAX8855ETJ+ Maxim Integrated Products, MAX8855ETJ+ Datasheet - Page 12

• Manufacturer Part Number: MAX8855ETJ+
• Description: IC REG STP DWN DUAL 5A 32-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX8855ETJ+

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: 0.6 ~ 3.24 V
• Current - Output: 5A
• Frequency - Switching: 500kHz ~ 2MHz
• Voltage - Input: 2.35 ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Power - Output: 2.76W
• Output Current: 5 A
• Input Voltage: 2.35 V to 3.6 V
• Supply Current: 2.8 mA
• Switching Frequency: 2 MHz
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Dual, 5A, 2MHz Step-Down Regulator
In Figure 3d, EN1 and EN2 are connected together and
driven as a single input. Although both outputs begin
ramping up at the same time, slope matching is
achieved by selecting the SS_ capacitors. See the
Setting the Soft-Start Time section for information on
selecting the SS_ capacitors. In Figure 3d, the slope of
the output voltages during soft-start is equal. This is
achieved by setting the ratio of the soft-start capacitors
equal to the ratio of the output voltages:
The MAX8855 operates from 500kHz to 2MHz using
either its internal oscillator, or an externally supplied
clock. See the Setting the Switching Frequency section.
Thermal-overload protection limits the total power dissi-
pation of the MAX8855. Internal thermal sensors monitor
the junction temperature at each of the regulators. When
the junction temperature exceeds +165°C, the corre-
sponding regulator is shut down, allowing the IC to cool.
The thermal sensor turns the regulator on after the junc-
tion temperature cools by +20°C. In a continuous ther-
mal-overload condition, this results in a pulsed output.
Figure 3d. Startup and Sequencing Options—Matching Startup Slopes of Output Voltages with Internal Reference
12
______________________________________________________________________________________
Thermal-Overload Protection
C
C
SS
SS
Synchronization (FSYNC)
1
2
=
V
V
OUT
OUT
1
2
The output voltages for regulator 1 (with REFIN con-
nected to SS1) and regulator 2 are set with a resistor
voltage-divider connected from the output to FB_ to
GND as shown in Figure 4. Select a value for the resis-
tor connected from output to FB_ (R4 in Figure 4)
between 2kΩ and 10kΩ. Use the following equations to
find the value for the resistor connected from FB_ to
GND (R6 in Figure 4):
Figure 4. Type III Compensation Network
MAX8855
PWRGD1
PWRGD2
OUT1
OUT2
EN
COMP_
R
6
FB_
LX_
=
(
Setting the Output Voltage
10kΩ
10kΩ
V
OUT
0 6
L
_
.
Design Procedure
R7
−
0 6
C
.
O
PWRGD1
PWRGD2
V
SS1
C10
DD
)
C9
×
R
4
REFIN
EN2
SS2
EN1
R4
R6
OUTPUT
R8
C11
EN