MAX1845 Maxim, MAX1845 Datasheet - Page 8

• Manufacturer Part Number: MAX1845
• Description: Dual / High-Efficiency / Step-Down Controller with Accurate Current Limit
• Manufacturer: Maxim

(8A COMPONENTS, PWM MODE, V
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
(Circuit of Figure 1, components from Table 1, V
8
QSOP
1
2
3
4
5
6
_______________________________________________________________________________________
LOAD-TRANSIENT RESPONSE
PIN
QFN
32
33
34
35
1
2
20µs/div
NAME
OUT1
ILIM1
SKIP
TON
FB1
V+
OUT1
MAX1845 toc07b
= 1.8V)
Output Voltage Connection for the OUT1 PWM. Connect directly to the junction of the external
inductor and output filter capacitors. OUT1 senses the output voltage to determine the on-time
and also serves as the feedback input in fixed-output modes.
Feed b ack Inp ut for O U T1. C onnect to G N D for 1.8V fi xed outp ut or to V
connect to a r esi stor - d i vi d er netw or k fr om O U T1 for an ad j ustab l e outp ut b etw een 1V and 5.5V .
Current-Limit Threshold Adjustment for OUT1. The current-limit threshold at CS1 is 0.1 times the
voltage at ILIM1. Connect a resistor-divider network from REF to set the current-limit threshold
between 25mV and 250mV (with 0.25V to 2.5V at ILIM). Connect to V
current-limit threshold.
Battery Voltage-Sense Connection. Connect to input power source. V+ is only used to adjust the
DH_ on-time for pseudofixed-frequency operation.
On-Time Selection Control Input. This four-level input pin sets the DH_ on-time to determine the
operating frequency.
Pulse-Skipping Control Input. Connect to V
to enable pulse-skipping operation.
V
100mV/div
I
5A/div
OUT1
OUT1
(4A COMPONENTS, SKIP = GND, V
AGND
Open
TON
V
REF
IN
CC
Typical Operating Characteristics (continued)
= 15V, SKIP = GND, TON = unconnected, T
STARTUP WAVEFORM
400µs/div
FREQUENCY (OUT1) (kHz)
OUT2
MAX1845 toc09
CC
= 2.5V)
FUNCTION
for low-noise forced-PWM mode. Connect to AGND
620
485
345
235
V
1V/div
I
2A/div
OUT2
OUT2
(4A COMPONENTS, SKIP = GND, V
A
= +25°C, unless otherwise noted.)
SHUTDOWN WAVEFORM
CC
C C
FREQUENCY (OUT2) (kHz)
Pin Description
for 1.5V fi xed outp ut, or
to assert 50mV default
100µs/div
460
355
255
170
OUT2
MAX1845 toc09
= 2.5V)
V
1V/div
I
5A/div
OUT2
OUT2