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ISL78235 Schematic ( PDF Datasheet ) - Intersil Corporation

Teilenummer ISL78235
Beschreibung 5A Automotive Synchronous Buck Regulator
Hersteller Intersil Corporation
Logo Intersil Corporation Logo 




Gesamt 20 Seiten
ISL78235 Datasheet, Funktion
DATASHEET
5A Automotive Synchronous Buck Regulator
ISL78235
The ISL78235 is a highly efficient, monolithic, synchronous
step-down DC/DC converter that can deliver 5A of continuous
output current from a 2.7V to 5.5V input supply. The device uses
peak current mode control architecture to achieve very low duty
cycle operation at high frequency with fast transient response and
excellent loop stability.
The ISL78235 integrates a low ON-resistance P-Channel
(35mΩ, typ) high-side FET and N-Channel (11mΩ, typ) low-side
FET to maximize efficiency and minimize external component
count. The 100% duty cycle operation allows less than 250mV
dropout voltage at 5A output current. The operating frequency
of the Pulse Width Modulator (PWM) is adjustable from
500kHz to 4MHz. The default switching frequency of 2MHz is
set by connecting the FS pin high.
The ISL78235 can be configured for discontinuous (PFM) or
forced continuous (PWM) operation at light load. Forced
continuous operation reduces noise and RF interference, while
discontinuous mode provides higher efficiency by reducing
switching losses at light loads.
Fault protection is provided by internal hiccup mode current
limiting during short circuit and overcurrent conditions. The
device also integrates output over voltage and
over-temperature protections. A power-good monitor indicates
when the output is in regulation. The ISL78235 offers a 1ms
Power-Good (PG) timer at power-up.
When in shutdown, the ISL78235 discharges the output
capacitor through an internal 100Ω soft-stop switch. Other
features include internal fixed or adjustable soft-start and
internal/external compensation.
The ISL78235 is available in a 3mmx3mm 16 Ld Thin Quad Flat
No-Lead (TQFN) Pb-free package with an exposed pad for
improved thermal performance. The ISL78235 is rated to
operate across the temperature range of -40°C to +105°C.
Features
• 2.7 to 5.5V input voltage range
• 2MHz default switching frequency
• 100ns guaranteed phase min on time for wide output
regulation
• Adjustable switching frequency from 500kHz to 4MHz
• External synchronization from 1MHz to 4MHz
• Optional PFM mode for light-load efficiency improvement
• Very low ON-resistance HS/LS switches: 35mΩ/11mΩ
• Internal 1ms or adjustable external soft-start
• Soft-stop output discharge during disable
• OTP, OCP, Output OVP, Input UVLO Protections
• 1% reference accuracy over-temperature
• Up to 95% efficiency
• AEC-Q100 qualified
• Common pinout family allows migration from 3A to 5A
without PCB change:
- ISL78233 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3A
- ISL78234 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4A
- ISL78235 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5A
Applications
• DC/DC POL modules
μC/µP, FPGA and DSP power
• Video processor/SOC power
• Li-ion battery powered devices
• Automotive infotainment power
Related Literature
UG015, “ISL7823xEVAL1Z Evaluation Board User Guide”
ISL78233, ISL78234 Datasheet
L
2.7V TO 5.5V
COUT
CIN
16 15 14 13
VIN 1
VDD 2
PG 3
*ISL78235
PGND
12
PGND
11
SGND
10
SYNC 4
FB
9
56 78
VOUT 5A LOAD
DSP, FPGA
*Pin Compatible
ISL78233 - 3A BUCK
ISL78234 - 4A BUCK
100
90
2.5VOUT
80 3.3VOUT
1.8VOUT 1.5VOUT
1.2VOUT
70
60
50
TA = +25°C
40
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT LOAD (A)
FIGURE 1. TYPICAL APPLICATION: 5A BUCK REGULATOR
FIGURE 2. EFFICIENCY vs LOAD (VIN = 5V; fsw = 2MHz; SYNC = GND)
February 20, 2015
FN8713.1
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2015. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.






ISL78235 Datasheet, Funktion
ISL78235
Electrical Specifications Specification limits are established at the following conditions: TA = -40°C to +105°C, VIN = 3.6V, EN = VIN,
unless otherwise noted. Typical values are at TA = +25°C. Boldface limits apply across the operating temperature range - 40°C to +105°C. (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN MAX
(Note 7) TYP (Note 7) UNITS
COMPENSATION
Error Amplifier Transconductance
COMP = VDD, Internal compensation
125 µA/V
External compensation
130 µA/V
Transresistance
RT
0.11 0.17 0.22
Ω
MOSFET
P-Channel ON-resistance
N-Channel ON-resistance
PHASE
VIN = 5V, IO = 200mA
VIN = 2.7V, IO = 200mA
VIN = 5V, IO = 200mA
VIN = 2.7V, IO = 200mA
26 35 50 mΩ
38 52 78 mΩ
5 11 20 mΩ
8 15 31 mΩ
PHASE Maximum Duty Cycle
100 %
PHASE Minimum On-time
SYNC = High
100 ns
OSCILLATOR
Nominal Switching Frequency
fSW FS = VIN
FS with RS = 402kΩ
1730
2000
420
2350
kHz
kHz
FS with RS = 42.2kΩ
4200
kHz
SYNC Logic Low to High Threshold
0.67 0.75 0.84
V
SYNC Logic Hysteresis
0.1 0.17 0.2
V
SYNC Logic Input Leakage Current
SYNC = 3.6V
3.7 5
µA
POWER-GOOD (PG)
Output Low Voltage
IPG = 1mA
0.3 V
PG Delay Time (Rising Edge)
PG Delay Time (Falling Edge)
Time from VOUT reached regulation
0.5 1
2 ms
6.5 µs
PG Pin Leakage Current
OVP PG Rising Threshold
PG = VIN
0.01
0.80
0.1
µA
V
UVP PG Rising Threshold
80 85 90
%
UVP PG Hysteresis
5.5 %
EN
Logic Input Low
0.4 V
Logic Input High
0.9 V
EN Logic Input Leakage Current
EN = 3.6V
0.1 1
µA
OVER-TEMPERATURE PROTECTION
Thermal Shutdown
Temperature Rising
150 °C
Thermal Shutdown Hysteresis
Temperature Falling
25 °C
NOTE:
7. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
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FN8713.1
February 20, 2015

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ISL78235 pdf, datenblatt
ISL78235
Typical Operating Performance Unless otherwise noted, operating conditions are: TA = +25°C, VIN = VDD = 5V,
VOUT = 1.8V, EN = VDD, SYNC = VDD, L = 0.68µH, fSW = 2MHz, CIN = 2 x 22µF, COUT = 2 x 22µF, IOUT = 0A to 5A. (Continued)
VOUT 100mV/DIV AC
COUT = 4x22µF
VOUT 100mV/DIV AC
COUT = 4x22µF
I_LOAD 2A/DIV
Rcomp = 154kΩ
Ccomp = 220pF
I_LOAD 2A/DIV
Rcomp = 154kΩ
Ccomp = 220pF
500µs/DIV
FIGURE 33. LOAD TRANSIENT 0A TO 5A; 0.5A/µs (SYNC = GND)
500µs/DIV
FIGURE 34. LOAD TRANSIENT 0A TO 5A; 0.5A/µs (SYNC = VDD)
VOUT
PG
I_PHASE
PHASE
FIGURE 35. OUTPUT SHORT CIRCUIT
CSS = 33nF
SS
I_PHASE
VOUT
I_LOAD
FIGURE 37. SHORT CIRCUIT HICCUP WAVEFORM
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PHASE
PG
VOUT
I_PHASE
FIGURE 36. OUTPUT SHORT CIRCUIT RECOVERY TO 1A LOAD
PHASE
LOAD = 4A TO 8A STEP
I_PHASE
VOUT
PG
FIGURE 38. OVERCURRENT PROTECTION
FN8713.1
February 20, 2015

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