ISL8036AIRZ Intersil, ISL8036AIRZ Datasheet - Page 23

• Manufacturer Part Number: ISL8036AIRZ
• Description: IC REG SYNC BUCK DUAL 3A 24QFN
• Manufacturer: Intersil
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of ISL8036AIRZ

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 V ~ 6 V
• Current - Output: 3A
• Frequency - Switching: 2.5MHz
• Voltage - Input: 2.85 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

are reset and soft-start is attempted again. If the
overcurrent condition goes away prior to the OC Fault
Counter reaching a count of four, the Overcurrent
Condition Flag will set back to LOW.
If the negative output current reaches -2.5A, the part
enters Negative Overcurrent Protection. At this point, all
switching stops and the part enters tri-state mode while
the pull-down FET is discharging the output until it
reaches normal regulation voltage, then the IC restarts.
PG
There are two independent power-good signals. PG1
monitors the Output Channel 1 and PG2 monitors the
Output Channel 2. When powering up, the open-collector
Power-on Reset output holds low for about 1ms after V
reaches the preset voltage. The PG_ output also serves
as a 1ms delayed Power-Good signal.
UVLO
When the input voltage is below the undervoltage lock
out (UVLO) threshold, the regulator is disabled.
Enable
The enable (EN) input allows the user to control the
turning on or off the regulator for purposes such as
power-up sequencing. When the regulator is enabled,
there is typically a 600µs delay for waking up the
bandgap reference. Then the soft start-up begins.
Soft-start-up
The soft-start-up eliminates the inrush current during the
start-up. The soft-start block outputs a ramp reference to
both the voltage loop and the current loop. The two
ramps limit the inductor current rising speed as well as
the output voltage speed so that the output voltage rises
in a controlled fashion. At the very beginning of the start-
up, the output voltage is less than 0.5V; hence the PWM
operating frequency is 1/2 of the normal frequency.
When the IC ramps up at start-up, it can't sink current
even at PWM mode, behaving like in diode emulated
mode for the soft-start time.
Discharge Mode (Soft-Stop)
When a transition to shutdown mode occurs, or the
output undervoltage fault latch is set, its output
discharges to PGND through an internal 100Ω switch.
Power MOSFETs
The power MOSFETs are optimize for best efficiency. The
ON -resistance for the P-MOSFET is typically 50mΩ and
the ON-resistance for the N-MOSFET is typical 50mΩ.
100% Duty Cycle
The ISL8036, ISL8036A features 100% duty cycle
operation to maximize the battery life. When the battery
voltage drops to a level that the ISL8036, ISL8036A can
no longer maintain the regulation at the output, the
regulator completely turns on the P-MOSFET. The
maximum drop-out voltage under the 100% duty-cycle
23
ISL8036, ISL8036A
O
operation is the product of the load current and the ON-
resistance of the P-MOSFET.
Thermal Shutdown
The ISL8036, ISL8036A has built-in thermal protection.
When the internal temperature reaches +150°C, the
regulator is completely shutdown. As the temperature
drops to +125°C, the ISL8036, ISL8036A resumes
operation by stepping through a soft start-up.
Applications Information
Output Inductor and Capacitor Selection
To consider steady state and transient operation,
ISL8036, ISL8036A typically uses a 1.5µH output
inductor. Higher or lower inductor value can be used to
optimize the total converter system performance. For
example, for a higher output voltage 3.3V application, in
order to decrease the inductor current ripple and output
voltage ripple, the output inductor value can be
increased. The inductor ripple current can be expressed
in Equation 2:
The inductor’s saturation current rating needs be at least
larger than the peak current. The ISL8036, ISL8036A
protects the typical peak current 4.8A. The saturation
current needs be over 4.8A for maximum output current
application.
ISL8036, ISL8036A uses an internal compensation
network and the output capacitor value is dependent on
the output voltage. The ceramic capacitor is
recommended to be X5R or X7R. The recommended
minimum output capacitor values for the ISL8036,
ISL8036A are shown in Table 4.
In Table 4, the minimum output capacitor value is given
for different output voltages to make sure the whole
converter system is stable.
Output Voltage Selection
The output voltage of the regulator can be programmed
via an external resistor divider, which is used to scale the
ΔI
TABLE 4. OUTPUT CAPACITOR VALUE vs V
=
V
-------------------------------------- -
O
V
(V)
0.8
1.2
1.6
1.8
2.5
3.3
3.6
•
OUT
L f
⎛
⎜
⎝
1
•
ISL8036, ISL8036A
–
S
---------
V
V
IN
O
⎞
⎟
⎠
2 x 6.8
2 x 22
2 x 22
2 x 22
2 x 22
2 x 22
C
(µF)
OUT
10
1.0~2.2
1.0~2.2
1.0~2.2
1.0~3.3
1.0~3.3
1.0~4.7
1.0~4.7
OUT
October 18, 2010
(µH)
L
FN6853.1
(EQ. 2)