MAX1606 Datasheet, PDF (7/10 Pages) Maxim Integrated Products – 28V Internal Switch LCD Bias Supply with True Shutdown

28V Internal Switch LCD Bias Supply
with True Shutdown
V_IN = 0.8V TO 5.5V
BATT
C2
V_CC = 2.4V TO 5.5V
V_CC
C1
LIM
ON
OFF
SHUTDOWN
LOGIC
SHDN
MAX1606
LOGIC
CONTROL
CURRENT
LIMIT
I_LIM
ERROR
AMPLIFIER
1.25V
SW
L1
10µH
D1
LX
N
V_OUT = V_IN TO 28V
C_OUT
C_FF
R1
FB
R2
Figure 1. Functional Diagram
V_CC
(2.4V TO 5.5V)
V_CC
MAX1606
LIM
V_CC
(2.4V TO 5.5V)
V_CC
NO CONNECTION
MAX1606
LIM
V_CC
(2.4V TO 5.5V)
V_CC
MAX1606
LIM
GND
IPEAK = 500mA
Figure 2. Setting the Peak Inductor Current Limit
GND
IPEAK = 250mA
GND
IPEAK = 125mA
Detailed Description
The MAX1606 step-up DC-DC converter operates from a
2.4V to 5.5V supply and converts voltages as low as
0.8V up to 28V. The device includes an internal switch-
ing MOSFET with a 0.8Ω on-resistance and selectable
current limit (Figure 1) and consumes 160µA of supply
current. During startup, the MAX1606 extends the mini-
mum off-time, limiting initial battery surge current. The
MAX1606 uses a P-channel MOSFET to isolate the out-
put from the input during true shutdown mode. This isola-
tion switch also includes short-circuit current limiting,
which protects the inductor and diode during a short-cir-
cuit fault.
Control Scheme
The MAX1606 features a minimum off-time, current-limit-
ed control scheme. The duty cycle is governed by a pair
of one-shots that set a minimum off-time and a maximum
on-time. The switching frequency can be up to 500kHz
and depends upon the load and input voltage. The peak
current limit of the internal N-channel MOSFET is pin
selectable and may be set at 125mA, 250mA, or 500mA
(Figure 2).
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