ISL6567 Datasheet, PDF (9/26 Pages) Intersil Corporation – Multipurpose Two-Phase Buck PWM Controller with Integrated MOSFET Drivers

ISL6567
FS (Pin 22)
This pin is used to set the switching frequency. Connect a
resistor, R_FS, from this pin to ground and size it according to
the graph in Figure 1 or Equation 2:
R_FS
=
(
10
10.61
–
( 1.035
⋅
log
(
FS
W
)))
(EQ. 2)
200k
PGOOD (Pin 21)
This pin represents the output of the on-board power-good
monitor. Thus, the FB pin is monitored and compared against
a window centered around the available reference; an FB
voltage within the window disables the open-collector output,
allowing the external resistor to pull-up PGOOD high.
Approximate pull-down device impedance is 65Ω.
While operating with an external reference, the power-good
function is enabled once the MON pin amplitude exceeds its
monitored threshold (typically 300mV).
100k
50k
20k
10k
100k
200k
500k
1M
2M
SWITCHING FREQUENCY (Hz)
FIGURE 1. SWITCHING FREQUENCY vs R_FS VALUE
COMP
R2
C1
FB
R1
VDIFF
REFERENCE
OSCILLATOR
PWM
Σ
CIRCUIT
PWM
Σ
CIRCUIT
Σ
AVERAGE
Σ
VSEN
RGND
ISL6567
V_IN
UGATE1
HALF-BRIDGE
DRIVE
HALF-BRIDGE
DRIVE
CURRENT
SENSE
CURRENT
SENSE
PHASE1
LGATE1
L1
R_ISEN1
ISEN1
V_IN
L2
UGATE2
PHASE2
LGATE2
ISEN2
R_ISEN2
V_OUT
C_OUT
FIGURE 2. SIMPLIFIED BLOCK DIAGRAM OF THE ISL6567 VOLTAGE AND CURRENT CONTROL LOOPS
9
FN9243.3
May 28, 2009