EL7520ILZ-T13 Intersil, EL7520ILZ-T13 Datasheet - Page 11

• Manufacturer Part Number: EL7520ILZ-T13
• Description: IC CTRLR DC/DC 4-CHAN 20-QFN
• Manufacturer: Intersil
• Type: Step-Up (Boost)r

Specifications of EL7520ILZ-T13

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 4
• Current - Output: 40mA
• Frequency - Switching: 1MHz
• Voltage - Input: 3 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-VQFN Exposed Pad, 20-HVQFN, 20-SQFN, 20-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Power - Output: -

The internal current limit circuitry is shown in Figure 26. The
circuit senses the voltage across the R
MOSFET is on; then compare it to the internal voltage
reference to realize the current limit. The internal voltage
reference is generated by a 10µA current and any additional
current set at I
voltage reference is based on the following equation:
V
Where V
Where V
The external resistor R
100K to generate µA of current.
I
V
SAD
THRESHOLD
ISAD
=
=
V
---------------- -
ISAD
BE
ISAD
V
R1
REF
≈ 0.7V
is the voltage at pin I
SAD
=
–



V
V
---------------- -
BE
ISAD
R
pin flowing through an 8kΩ resistor. The
V
1
REF
–
COMPARATOR
1K
1
AMPLIFIER
+
should be chosen in the order of
10µA
×
UVLO
GENERATOR
REFERENCE
GM
I
SAD
11



×
FIGURE 25. FUNCTION DIAGRAM OF THE BOOST CONTROLLER
8K
SAD
COMPENSATION
DS(ON)
SHUTDOWN
.
& STARTUP
AMPLIFIER
VOLTAGE
CONTROL
SLOPE
when the
OSCILLATOR
Σ
EL7520, EL7520A
CURRENT LIMIT
COMPARATOR
CONTROLLER
AMPLIFIER
CURRENT
LOGIC
PWM
OSC
Hence the maximum output current is determined by the
following equation:
I
Where ∆I
set by:
∆I
f
D
R
OMAX
S
1
L
=
is the switching frequency; D is the duty cycle.
=
V
----------------------- -
O
V
---------
GENERATOR
V
=
L
V
FIGURE 26. CURRENT LIMIT BLOCK DIAGRAM
IN
CURRENT
LIMIT REF
–
REF
BUFFER
O



L
V
×
I
V
---------------------------------------
SAD
IN
is the peak to peak inductor ripple current, and is
THRESHOLD
---- -
f
D
S
R
DSON
1K
V
DD
10µA
DRVB
I
I
–
SIN
SAD
∆I
--------
8K
2
L
+


-
×
V
V
---------
IN
V
IN
O
CONTROLLER
LOGIC
V
BOOST
DRVB
I
SIN
July 12, 2005
FN7318.0
LX