ISL6237IRZ Intersil, ISL6237IRZ Datasheet - Page 30

• Manufacturer Part Number: ISL6237IRZ
• Description: IC MAIN PWR CTRLR QUAD 32-QFN
• Manufacturer: Intersil

Specifications of ISL6237IRZ

• Applications: Controller, Notebook Computers
• Voltage - Input: 5.5 ~ 25 V
• Number Of Outputs: 4
• Operating Temperature: -40°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -

Adjustable-Output Feedback (Dual-Mode FB)
Connect FB1 to GND to enable the fixed 5V or tie FB1 to
VCC to set the fixed 1.5V output. Connect a resistive
voltage-divider at FB1 between OUT1 and GND to adjust the
respective output voltage between 0.7V and 5.5V
(Figure 72). Choose R
for R
where V
Likewise, connect REFIN2 to VCC to enable the fixed 3.3V
or tie REFIN2 to a 3.3V supply to set the fixed 1.05V output.
Set REFIN2 from 0 to 2.50V for SMPS2 tracking mode
(Figure 73).
where:
• VR = 2V nominal (if tied to REF)
Design Procedure
Establish the input voltage range and maximum load current
before choosing an inductor and its associated ripple-current
ratio (LIR). The following four factors dictate the rest of the
design:
LOW
“>2.5” → HIGH
“>2.5” → HIGH
“>2.5” → HIGH
“>2.5” → HIGH
“>2.5” → HIGH
“>2.5” → HIGH
1. Input Voltage Range. The maximum value (V
2. Maximum Load Current. The peak load current
R3
R
1
must accommodate the maximum AC adapter voltage.
The minimum value (V
lowest input voltage after drops due to connectors, fuses
and battery selector switches. Lower input voltages result
in better efficiency.
(I
stress and filtering requirements and thus drives output
capacitor selection, inductor saturation rating and the
design of the current-limit circuit. The continuous load
current (I
the selection of input capacitors, MOSFETs and other
critical heat-contributing components.
VEN_LDO
1
=
LOAD(MAX)
=
using Equation 5.
R4
R
FB1
2
⋅
⋅
⎛
⎜
⎝
⎛
⎝
V
------------------ - 1
= 0.7V nominal.
------------------ - 1
V
LOAD
V
OUT1
OUT2
VR
FB1
) determines the instantaneous component
) determines the thermal stress and drives
–
–
⎞
⎟
⎠
⎞
⎠
2
VEN1 (V)
to be approximately 10k and solve
HIGH
HIGH
HIGH
LOW
LOW
LOW
REF
IN(MIN)
30
) must account for the
TABLE 4. SHUTDOWN AND STANDBY CONTROL LOGIS
VEN2 (V)
HIGH
HIGH
HIGH
LOW
LOW
LOW
REF
IN(MAX)
(EQ. 5)
(EQ. 6)
)
ISL6237
LDO
OFF
ON
ON
ON
ON
ON
ON
3. Switching Frequency. This choice determines the basic
4. Inductor Ripple Current Ratio (LIR). LIR is the ratio of the
FIGURE 72. SETTING V
trade-off between size and efficiency. The optimal
frequency is largely a function of maximum input voltage
and MOSFET switching losses.
peak-peak ripple current to the average inductor current.
Size and efficiency trade-offs must be considered when
setting the inductor ripple current ratio. Low inductor
values cause large ripple currents, resulting in the
smallest size, but poor efficiency and high output noise.
Also, total output ripple above 3.5% of the output
regulation will cause controller to trigger out-of-bound
condition. The minimum practical inductor value is one
that causes the circuit to operate at critical conduction
(where the inductor current just touches zero with every
cycle at maximum load). Inductor values lower than this
grant no further size-reduction benefit.
The ISL6237 pulse-skipping algorithm (SKIP = GND)
initiates skip mode at the critical conduction point, so the
inductor's operating point also determines the load
current at which PWM/PFM switchover occurs. The
optimum LIR point is usually found between 25% and
50% ripple current.
ISL6237
ISL88732
ISL88732
ISL88733
ISL6237
ISL88733
ISL88734
ISL88734
UGATE_
UGATE1
UGATE_
ON (AFTER SMPS2 IS UP)
LGATE_
LGATE1
LGATE_
VOUT_
VOUT_
OUT1
LGATE1
UGATE1
FB_
FB1
FB_
OUT1
FB1
SMPS1
OFF
OFF
OFF
ON
ON
ON
OUT1
Q
Q
V
WITH A RESISTOR DIVIDER
4
IN
3
ON (AFTER SMPS1 IS UP)
R
R
1
2
SMPS2
OFF
OFF
OFF
ON
ON
ON
March 18, 2008
OUT1
FN6418.4