ISL6567CRZ Intersil, ISL6567CRZ Datasheet - Page 17

• Manufacturer Part Number: ISL6567CRZ
• Description: IC CTLR PWM 2PHASE BUCK 24-QFN
• Manufacturer: Intersil

Specifications of ISL6567CRZ

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 1.5MHz
• Duty Cycle: 66%
• Voltage - Supply: 4.9 V ~ 5.5 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 24-VQFN
• Frequency-max: 1.5MHz
• Rohs Compliant: YES
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Specifications” table starting on page 5 ). Once these
conditions are met, the controller immediately initiates a
soft-start sequence.
General Application Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multi-phase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced in the
following. In addition to this guide, Intersil provides complete
reference designs that include schematics, bills of materials,
and example board layouts for typical applications.
BIAS SUPPLY CONSIDERATIONS
The ISL6567 features an on-board shunt regulator capable of
sinking up to 100mA (minimally). This integrated regulator can
be used to produce the necessary bias voltage for the
controller and the MOSFETs. The integrated regulator can be
utilized directly, via a properly sized resistor, as shown in
Figure 17, or via an external NPN transistor and additional
resistors when either the current needed or the power being
dissipated becomes too large to be handled inside the
ISL6567 in the given operating environment.
A first step in determining the feasibility and selecting the
proper bias regulator configuration consists in determining
the maximum bias current required by the circuit. While the
bias current required by the ISL6567 is listed in the
“Electrical Specifications” table starting on page 5, the bias
current required by the controlled MOSFETs needs be
calculated. Equation 10 helps determine this bias current
function of the sum of the gate charge of all the controlled
MOSFETs at 5V V
frequency, F
FIGURE 17. INTERNAL SHUNT REGULATOR USE WITH
SHUNT REG
E/A
CIRCUIT
POR
+
-
SW
VREF
EXTERNAL RESISTOR (PASSIVE
CONFIGURATION)
:
GS
ISL6567
, Q
GTOTAL
17
VREG
VCC
PVCC
EXTERNAL CIRCUIT
, and the switching
R
BIAS
V
IN
ISL6567
Total required bias current, I
bias current, I
The maximum bias current, I
the internal shunt regulator and a simple external resistor is
characterized in Figure 18 and can also be determined using
Equation 11.
To exemplify the use, for an input voltage ranging from 10V
to 14V, find the intersection of the ΔV
V
find the maximum bias current obtainable (approximately
56% of the maximum current obtainable via the integrated
shunt regulator, I
Once the maximum obtainable bias current, I
determined, and providing it is greater than the bias current,
I
based on the lowest input voltage, V
Figure 19 helps with a quick resistor selection based on the
previous guidelines presented. Divide the value thus
obtained by the maximum desired bias current, I
obtain the actual resistor value to be used.
I
I
R
BIAS
BIASMAX
B
FIGURE 18. NORMALIZED MAXIMUM BIAS CURRENT
I
INmin
BIAS
BIAS
≅
90
80
70
60
50
40
30
20
10
Q
0
, required by the circuit, R
GTOTAL
=
=
= 10V mark and project the result on the Y axis to
ΔV
ΔV
ΔV
ΔV
V
------------------------------------------
I
IN
IN
IN
VCC
IN
=
6
INMIN
= 1V
= 2V
= 3V
= 4V
I
OBTAINABLE IN PASSIVE CONFIGURATION vs
INPUT VOLTAGE RANGE CHARACTERISTIC;
V
VREGMAX
VCC
⋅
I
VCC
BIAS
+
F
SW
I
VREG_MAX
–
B
, to that required by the MOSFETs, I
V
= 5V
7
VCC
⋅
------------------------------------------- -
V
V
INMAX
INMIN
BIAS
).
8
BIAS
V
INmin
SHUNT
–
–
, sums up the ISL6567’s
, that can be obtained via
V
V
VCC
(V)
VCC
INMIN
IN
9
can be determined
= 4V curve with the
:
BIAS_MAX
10
BIAS
ΔV
ΔV
ΔV
ΔV
May 28, 2009
IN
IN
IN
IN
(EQ. 10)
, to
(EQ. 11)
(EQ. 12)
FN9243.3
B
= 5V
= 6V
= 7V
= 8V
11
, is
.