ISL6520B Datasheet, PDF (8/10 Pages) Intersil Corporation – Single Synchronous Buck Pulse-Width Modulation PWM Controller

ISL6520B
through protection present aboard the ISL6520B may be
circumvented by these MOSFETs if they have large parasitic
impedences and/or capacitances that would inhibit the gate
of the MOSFET from being discharged below it’s threshold
level before the complementary MOSFET is turned on.
+5V
D_BOOT
VCC
ISL6520B
+ V_D -
+5V
BOOT
C_BOOT
Q1
UGATE
PHASE
Q2
-
LGATE
+
GND
NOTE:
V_G-S ≈ V_CC -V_D
NOTE:
V_G-S ≈ V_CC
FIGURE 6. UPPER GATE DRIVE BOOTSTRAP
Figure 6 shows the upper gate drive (BOOT pin) supplied by a
bootstrap circuit from V_CC. The boot capacitor, C_BOOT,
develops a floating supply voltage referenced to the PHASE
pin. The supply is refreshed to a voltage of V_CC less the boot
diode drop (V_D) each time the lower MOSFET, Q₂, turns on.
ISL6520B DC/DC Converter Application
Circuit
Figure 7 shows an application circuit of a DC/DC Converter.
Detailed information on the circuit, including a complete Bill-
of-Materials and circuit board description, can be found in
Application Note AN9932.
+5V
50kΩ
10.0kΩ
8200pF
1.00kΩ
0.1μF
ISL6520B
VCC
5
POR
AND
SOFT START
+
C_IN
2 x 330μF
1 _BOOT
COMP/SD 7
REF
470pF
+_-
FB 6
U₁
OSC
2 UGATE
8 PHASE
+_-
4 _LGATE
3
GND
3.16kΩ
60.4Ω
18000pF
2 x 1μF
D₁
0.1μF
Q₁
L₁
V_OUT
Q₂
C_OUT ⁺
0.1μF
3 x 330μF
Component Selection Notes:
C_IN - Each 330mF 6.3WVDC, Sanyo 6TPB330M or Equivalent.
C_OUT - Each 330mF 6.3WVDC, Sanyo 6TPB330M or Equivalent.
D1 - 30mA Schottky Diode, MA732 or Equivalent
L₁ - 3.1μH Inductor, Panasonic P/N ETQ-P6F2ROLFA or Equivalent.
Q₁, Q₂ - Fairchild MOSFET; HUF76143.
FIGURE 7. 5V TO 3.3V 15A DC/DC CONVERTER
8
FN9083.3
July 23, 2007