ISL6439 Datasheet, PDF (6/15 Pages) Intersil Corporation – Single Sync Buck PWM Controller for Broadband Gateway Applications

ISL6439, ISL6439A
Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted V_CC = 3.3V±5% and T_A = +25°C (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
GATE DRIVERS
Upper Gate Source Current
Upper Gate Sink Current
Lower Gate Source Current
Lower Gate Sink Current
PROTECTION / DISABLE
OCSET Current Source
Disable Threshold
I_UGATE-SRC V_BOOT - V_PHASE = 5V, V_UGATE = 4V
I_UGATE-SNK
I_LGATE-SRC V_VCC = 3.3V, V_LGATE = 4V
I_LGATE-SNK
I_OCSET
Commercial
Industrial
V_DISABLE
-
-1
-
A
-
1
-
A
-
-1
-
A
-
2
-
A
18
20
22
μA
16
20
22
μA
-
-
0.8
V
Functional Pin Description
14 LEAD SOIC
GND 1
14 UGATE
LGATE 2
CPVOUT 3
13 BOOT
12 PHASE
CT1 4
11 VCC
CT2 5
10 CPGND
OCSET 6
9 ENABLE
FB 7
8 COMP
16 LEAD 5x5 QFN
16 15 14 13
CPVOUT 1
CT1 2
CT2 3
OCSET 4
12 PHASE
11 VCC
10 CPGND
9 NC
5678
VCC
This pin provides the bias supply for the ISL6439. Connect a
well-decoupled 3.3V supply to this pin.
COMP and FB
COMP and FB are the available external pins of the error
amplifier. The FB pin is the inverting input of the internal
error amplifier and the COMP pin is the error amplifier
output. These pins are used to compensate the voltage-
control feedback loop of the converter.
GND
This pin represents the signal and power ground for the IC.
Tie this pin to the ground island/plane through the lowest
impedance connection available.
PHASE
Connect this pin to the upper MOSFET’s source. This pin is
used to monitor the voltage drop across the upper MOSFET
for overcurrent protection.
UGATE
Connect this pin to the upper MOSFET’s gate. This pin
provides the PWM-controlled gate drive for the upper
MOSFET. This pin is also monitored by the adaptive
shoot-through protection circuitry to determine when the
upper MOSFET has turned off.
BOOT
This pin provides ground referenced bias voltage to the
upper MOSFET driver. A bootstrap circuit is used to create a
voltage suitable to drive a logic-level N-Channel MOSFET.
LGATE
Connect this pin to the lower MOSFET’s gate. This pin provides
the PWM-controlled gate drive for the lower MOSFET. This pin
is also monitored by the adaptive shoot-through protection
circuitry to determine when the lower MOSFET has turned off.
OCSET
Connect a resistor (R_OCSET) from this pin to the drain of the
upper MOSFET (V_IN). R_OCSET, an internal 20μA current
source (I_OCSET), and the upper MOSFET on-resistance
(r_DS(ON)) set the converter overcurrent (OC) trip point
according to Equation 1:
I_PEAK
=
I_{--O-----C----S----E----T----}x_---R_{-----O----C----S----E----T--}
r_DS(ON)
(EQ. 1)
An overcurrent trip cycles the soft-start function.
ENABLE
This pin is the open-collector enable pin. Pulling this pin to a
level below 0.8V will disable the controller. Disabling the
ISL6439 causes the oscillator to stop, the LGATE and
UGATE outputs to be held low, and the softstart circuitry to
re-arm.
6
FN9057.5
November 5, 2008