LTC1558CGN-3.3 Linear Technology, LTC1558CGN-3.3 Datasheet - Page 5

• Manufacturer Part Number: LTC1558CGN-3.3
• Description: IC BACKUP BATT CNTRLR3.3V 16SSOP
• Manufacturer: Linear Technology
• Type: Charge Controllerr

Specifications of LTC1558CGN-3.3

• Function: Back-Up Management
• Battery Type: Nickel Cadmium (NiCd)
• Voltage - Supply: 2.9 V ~ 3.46 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Output Current: 330mA
• Output Voltage: 1.2V
• Operating Supply Voltage (min): 2.9V
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 3.465V
• Operating Temp Range: 0C to 70C
• Package Type: SSOP N
• Mounting: Surface Mount
• Pin Count: 16
• Operating Temperature Classification: Commercial
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

PIN
Pin Numbers are Shown First for the SO-8 Package
Then the GN16 and S16 Packages
SW (Pins 1/1, 2): Boost Converter Switching Node. Con-
nect a 22 H inductor from SW to the positive terminal of
the backup cell. In backup mode, this node is alternately
switched between ground and V
output voltage. In fast or trickle charge mode, an internal
regulator outputs a constant DC current from this pin
through the 22 H inductor and into the NiCd battery.
During power-up or undervoltage lockout (UVLO), the SW
pin enters a high impedance state.
GND (Pins 2/4): System Ground. The low power internal
circuitry returns to this pin in the 16-pin packages. GND
and PGND are bonded together to this pin in the SO-8.
CTL (Pins 3/5): Control. This pin provides three functions.
In backup mode this pin enters a high impedance state and
monitors the backup battery cell voltage (V
drops below 0.9V, the LTC1558 enters into UVLO. During
trickle charge mode, an external resistor R
trickle charge current. In all modes, pulling the CTL pin
below 250mV will generate either a “soft” or “hard” reset
pulse. See the Applications Information section for more
information.
FB (Pins 4/7): Output Voltage Feedback. This pin is fed to
the LTC1558’s internal comparators. The boost converter’s
output voltage is set with an external resistor divider
connected from V
mode when FB drops 7.5% below the internal reference
voltage (V
whenever FB drops below this (V
The LTC1558 exits backup mode when FB rises above
(V
RESET (Pins 5/11): System Reset, Active Low. This is an
open-drain output. This pin provides a low going reset
signal to the system processor. A 200ms pulse is gener-
ated if the CTL pin is pulled low for more than two seconds
(“hard” reset) or when the LTC1558 comes out of UVLO.
The “hard reset” stops the internal boost converter if it is
running. This pin is held low whenever the LTC1558 is in
UVLO and is guaranteed to be valid when V
than or equal to 1V.
REF
U
– 6%).
FUNCTIONS
REF
U
). During backup, the boost converter runs
BAK
U
to FB. The LTC1558 enters backup
BAK
REF
, generating the backup
– 7.5%) threshold.
BAT
CC
EXT
is greater
). If V
sets the
BAT
RESET also provides a low going 100 s signal if the CTL
pin is pulled low for less than two seconds (“soft” reset).
Unlike hard reset, soft reset does not affect the LTC1558’s
current operating mode.
BACKUP (Pins 6/13): Backup Active. This is an open-drain
output that pulls low unless the LTC1558 is in backup
mode. BACKUP signals the system controller that the
system is in backup mode so that it can reduce system
loading. BACKUP can also be used to drive the gate of a
P-channel MOSFET in series with the main system
regulator’s input. A 12V Zener diode is connected inter-
nally to this pin to act as a voltage clamp. See the
Applications Information section for more details.
V
except the boost converter are powered from this pin. A
0.1 F bypass capacitor is required from V
The UVLO detector inside the LTC1558 monitors V
V
9%, the LTC1558 enters UVLO mode and RESET is as-
serted. The LTC1558 will only exit from UVLO if V
to greater than – 6% of the rated output voltage. See the
Applications Information section for more details.
V
boost converter provides regulated output voltage to the
system through V
16-Pin GN and SO Package
PGND (Pin 3): Power Ground. The internal driver circuitry
returns to this pin. PGND should be connected to a low
impedance ground plane in close proximity to the NiCd
battery cell.
SHDN (Pin 6): Chip Shutdown. A TTL-compatible active
low voltage at SHDN puts the LTC1558 into low power
shutdown mode. In shutdown, all internal circuits power
down and are held in a reset state. The SW, CTL and V
pins enter into high impedance states. In shutdown mode,
supply current drops to below 50 A and current drawn
from the backup cell drops to below 15 A.
CC
CC
BAK
(Pins 7/14): Power Supply Input. All internal circuits
drops below the rated output voltage by greater than
(Pins 8/15, 16): Backup Supply Output. The LTC1558’s
LTC1558-3.3/LTC1558-5
BAK
during backup mode.
CC
to ground.
CC
rises
CC
5
BAK
.If