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PDF IS32BL3554 Data sheet ( Hoja de datos )
| Número de pieza | IS32BL3554 | |
| Descripción | BOOST TYPE LED DRIVER | |
| Fabricantes | ISSI | |
| Logotipo |  |
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IS32BL3554
BOOST TYPE LED DRIVER WITH 4-CHANNEL CURRENT SOURCE
Preliminary Information
July 2014
GENERAL DESCRIPTION
The IS32BL3554 is a white LED driver for backlight
applications based on a highly efficient boost
controller operating over a wide input voltage range of
4.5V to 33V.
The IS32BL3554 contains four regulated current
sources with 1.5% (Typ.) current matching between
strings for a uniform LED brightness. Each current
source can be programmed via an external resistor to
drive from 20mA to 180mA. A fast slew rate current
source allows high frequency and narrow pulse width
dimming signals to achieve a very high contrast ratio.
The device operating frequency can be adjusted from
0.1MHz to 1MHz.
The IS32BL3554 has safety protection features to
prevent damage during fault conditions. Protection
features include an internal soft-start circuit to prevent
a high inrush current during startup, open/short LED
protection to automatically disable a faulty current
source, over temperature protection (OTP),
cycle-by-cycle current limit, under voltage lockout
(UVLO), programmable OVP, VOUT short / Schottky
diode open protection and Schottky Diode
short-circuit protection.
The IS32BL3554 is available in a thermally enhanced
eTSSOP-16 package.
FEATURES
Input voltage range: 4.5V to 33V
4-Channel LED current sinks, 180mA per string
LED current adjustable from 20mA to 180mA
String-to-string current matching accuracy: 1.5%
Adjustable operating frequency: 100kHz to 1MHz
External PWM dimming
High contrast ratio
Less than 3µA shutdown current
Programmable soft-start
Built-in protection features
• OCP, OTP, UVLO
• Open/short LED protection
• Programmable OVP
• Schottky Diode/inductor short-circuit protection
Automotive AEC-Q100 qualified
APPLICATIONS
Automotive Lighting
LCD Monitor/TV
LCD Display Module
TYPICAL APPLICATION CIRCUIT
Figure 1 Typical Application Circuit
Integrated Silicon Solution, Inc. – www.issi.com
Rev. 0B, 07/23/2014
1
1 page  
IS32BL3554
ELECTRICAL CHARACTERISTICS (CONTINUED)
VIN =12V, VEN=5V, TA = TJ = -40°C ~ +125°C, Typical values are at TA = 25°C.
Symbol
Parameter
Condition
Min.
High Frequency Oscillator
tON-TIME
fOSC
DMAX
Minimum on-time
Switch frequency (10% variation)
Maximum duty cycle
Enable Logic And Dimming Logic
VEN_H
VEN_L
VDIM_H
VDIM_L
tPWM_MIN
EN high voltage
EN low voltage
PWM logic for external dimming
PWM dimming minimum pulse width
Power Switch Drive
VLIMIT
VLIMIT2
tLEB
Current limit threshold voltage
D/I short threshold voltage
Current sense LEB time
Compensation And Soft Start (COMP Pin)
GEA Error amplifier trans-conductance
IO_H Sourcing current
IO_L Sinking current
Over-Voltage Protection
VOVP OVP threshold voltage
VOVP_HYS OVP hysteresis
VOVP_SD Shutdown under abnormal condition
f = 500kHz (Note 1)
RT = 100kΩ
f = 500kHz
440
88
(Note 1)
2.4
2.5
(Note 1)
480
720
80
VCOMP=0.5V
VCOMP=2V
VOUT rising,
TA= -40°C, 25°C
VOUT rising,
TA= 125°C
55
60
1.8
1.8
200
3.0
Typ.
200
520
90
3/fOSC
560
800
100
2300
120
120
2.0
2.0
250
3.2
Max.
570
0.5
0.3
640
930
150
200
200
2.2
2.25
330
3.6
Unit
ns
kHz
%
V
V
V
V
µs
mV
mV
ns
µA/V
µA
µA
V
V
mV
V
Integrated Silicon Solution, Inc. – www.issi.com
Rev. 0B, 07/23/2014
5
5 Page 
IS32BL3554
Step 6c: Determining the peak input current IPEAK,
calculated as follows:
First calculate the ripple current IRIPPLE using Equation
(14):
I RIPPLE
tON VIN
L1
0.625 12 0.75 A
10
(14)
Then calculate the inductor peak current using
equation (15):
I PEAK I IN ( Avg ) 0.5 I RIPPLE
1.42 0.5 0.75 1.795 A
(15)
Step 6d: The peak current protect resistor RCS is
shown in Equation (16):
RCS
[]
0.8
I
0.54
PEAK [ A]
0.8 0.54 0.24
1.795
(16)
Choose a 0.235Ω resistor for RCS.
Generally a constant term, 0.8x, is added when
calculating the RCS value. A lower RCS value will result
in a higher IPEAK to prevent over current protection
errors.
Step 7: The boost converter requires a diode to carry
the inductor current during the MOSFET off time.
Schottky diodes are recommended due to their fast
recovery time and low forward voltage. D1 should be
rated to handle the maximum output voltage (plus
switching node ringing) and the peak switch current.
The conduction loss of the diode is calculated by:
PDIODE I RMS _ OFF V F
I2
RMS _ OFF
VIN
VOUT
I IN 2
I L
12
2
(17)
Where VF is the forward voltage of the Schottky diode.
Step 8: The IS32BL3554 integrates a soft start and
control loop compensation in COMP Pin. The soft start
feature allows the boost converter to gradually reach
its initial steady state output voltage, thereby reducing
startup stresses and current surges. The startup time
is controlled by an internal 130μA (ICS) current source
and the external compensation circuit composed of CC
and RC. When powering on, after the VIN UVLO
threshold is satisfied, the internal 130μA current
source charges the external capacitor CC. The COMP
pin voltage will ramp up slowly and limit the inrush
current during startup. The soft start time is determined
by the Equation (18):
t SS
VCOMP CC
I CS
(18)
Where VCOMP is the voltage of COMP pin and ICS is the
internal source current. Typically, a value of RC=1kΩ
and CC=0.22µF is sufficient for operating at 500kHz.
Low-ESR Surface-Mount Ceramic Capacitors (MLCCs)
are recommended. For most applications, ceramic
capacitors with X7R temperature characteristics are
preferred. These capacitors have tight capacitance
tolerance (as good as ±10%) and hold their value over
temperature (X7R: ±15% over -55°C to 125°C).
Step 9: The IS32BL3554 includes an internal low
dropout linear regulator with the output pin VCC. This
pin is used to power the internal PWM controller,
control logic and MOSFET driver. The regulator
generates a 5V supply when VIN≥5.5V. When VIN is
less than 5.5V, connect VCC directly to VIN.
The VCC pin should be decoupled with a 2.2μF
ceramic capacitor placed as close to the pin as
possible. This capacitor keeps VCC voltage steady
when the system operates at a high frequency. X7R
type ceramic capacitors should be used for decoupling
due to their good thermal stability.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. 0B, 07/23/2014
11
11 Page | ||
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